AO-001
ABERSON, S.D. Five-day tropical cyclone track forecasts in the North
Atlantic basin. Weather and Forecasting, 13(4):1005-1015 (1998).
Statistical analyses of the most recent 40 years of hurricane tracks
(1956-1995) are presented, leading to a version of the North Atlantic
climatology and persistence (CLIPER) model that exhibits much smaller
forecast biases but similar forecast errors compared to the previously
used version. Changes to the model involve the inclusion of more accurate
historical tropical cyclone track data and a simpler derivation of the
regression equations. Nonlinear systems analysis shows that the
predictability timescale in which the average errors increase by a factor
e is approximately 2.5 days in the Atlantic basin, which is larger than
that found by similar methods near Australia. This suggests that five-day
tropical cyclone track forecasts may have some benefit and, therefore, a
version of CLIPER extended to five days to be used as a baseline to
measure this skill is needed.
AO-002
ABERSON, S.D. Impact of the Gulfstream-IV jet aircraft on hurricane
forecasts. Minutes, 52nd Interdepartmental Hurricane Conference,
Clearwater, FL, January 26-30, 1998. Office of the Federal Coordinator
for Meteorological Services and Supporting Research, Washington, D.C.
(paper was mistakenly omitted from the Minutes) (1998).
No abstract.
AO-003
ABERSON, S.D. Targeted observations to improve tropical cyclone
forecasts. Scientific Programme, XXIII General Assembly, European
Geophysical Society, Nice, France, April 20-24, 1998. European
Geophysical Society, 256 (1998).
No abstract.
AO-004
ABERSON, S.D., M.A. Bender, and R.E. Tuleya. Ensemble forecasting of
tropical cyclone intensity. Preprints, Symposium on Tropical Cyclone
Intensity Change, American Meteorological Society 78th Annual Meeting,
Phoenix, AZ, January 11-16, 1998. American Meteorological Society,
Boston, 150-153 (1998).
No abstract.
AO-005
ABERSON, S.D., M.A. Bender, and R.E. Tuleya. Ensemble forecasting of
tropical cyclone tracks. Preprints, 12th Conference on Numerical Weather
Prediction, American Meteorological Society 78th Annual Meeting, Phoenix,
AZ, January 11-16, 1998. American Meteorological Society, Boston,
290-292 (1998).
No abstract.
AO-006
ABERSON, S.D., M.A. Bender, and R.E. Tuleya. Ensemble forecasting of
tropical cyclone tracks and intensity. Scientific Programme, XXIII
General Assembly, European Geophysical Society, Nice, France, April
20-24, 1998. European Geophysical Society, 255 (1998).
No abstract.
AO-007
ABERSON, S.D., R.E. Tuleya, and M.A. Bender. Ensemble forecasting of
hurricane track and intensity using the GFDL model during 1997. Minutes,
52nd Interdepartmental Hurricane Conference, Clearwater, FL, January
26-30, 1998. Office of the Federal Coordinator for Meteorological
Services and Supporting Research, Washington, D.C.,143-145 (1998).
Tropical cyclone track predictions have shown considerable skill past
three days, and intensity predictions are beginning to show some skill.
While most forecasts are good, great variability in the utility of
individual forecasts occurs. Ensemble forecasting provides a mechanism
by which the inherent uncertainty in model forecasts can be assessed.
During the 1996 and 1997 hurricane seasons, more than 100 sets of
ensemble forecasts using a two-mesh version of the Geophysical Fluid
Dynamics Laboratory (GFDL) hurricane model have been run, based upon the
bred growing modes produced operationally at the National Centers for
Environmental Prediction (NCEP). Results of these track and intensity
forecasts will be presented, including information as to how well the
models conform to the "perfect model" scenario, whether the forecasts
envelope the evolution of the atmosphere, and whether information on the
utility of individual model forecasts can be obtained from the
ensembles. Plans to continue ensemble forecasting runs during the 1998
hurricane season will be presented.
AO-008
ABERSON, S.D., R.E. Tuleya, and J. Heming. Five-day forecasts of tropical
cyclone tracks in the Atlantic basin. Minutes, 52nd Interdepartmental
Hurricane Conference, Clearwater, FL, January 26-30, 1998. Office of the
Federal Coordinator for Meteorological Services and Supporting Research,
Washington, D.C. (paper was mistakenly omitted from the Minutes) (1998).
Tropical cyclone track predictions have improved so that skill, as
assessed by the improvement of forecasts over a forecast provided by a
simple statistical model based upon climatology and persistence, averages
more than 30% at 72 h, the current standard length of forecasts. Because
of the possibility of such skill levels at longer forecast times during
the 1997 Atlantic hurricane season, four tropical cyclone track models
produced quasi-operational 120 h forecasts. The models were a new
version of CLIPER, with which to assess skill, and extensions of the
currently run VICBAR, GFDL, and UKMO models. Individual track forecasts
and skill assessments for the various models will be shown, and
recommendations for future work in this area, both operationally and for
research, will be made.
AO-009
Alfaro, E., L. Cid, and D.B. ENFIELD. Relationships between the start
and end date of the rainy season in Central America and the tropical
Atlantic and Pacific Oceans. Investigaciones Marinas, 26:59-69 (1998).
In recent years, several studies have shown that anomalies in the sea
surface temperature of the tropical Atlantic and Pacific Oceans are
related to variations in the intensity and timing of the rainy season in
Central America. In order to study anomalous behavior of the rainy season
over Central America, tropical Atlantic and Pacific Oceans indices are
used to produce correlation series with the starting and ending date
(IELL and TELL) of the rainy season. The North Atlantic (ATN) and
SOI-Niño3 indices show the main correlations with the IELL and the TELL,
respectively.
AO-010
AMAT, L.R., M.D. POWELL, and S.H. HOUSTON. WANDA: HRD's real-time
tropical cyclone "Wind Analysis Distributed Application." Preprints,
16th Conference on Weather Analysis and Forecasting, Symposium on the
Research Foci of the U.S. Weather Research Program, American
Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16,
1998. American Meteorological Society, Boston, J29-J31 (1998).
No abstract
AO-011
Asher, W.E., and R.H. WANNINKHOF. The effect of bubble-mediated gas
transfer on purposeful dual gaseous-tracer experiments. Journal of
Geophysical Research, 103(C5):10,555-10,560 (1998).
For air-water gas exchange across unbroken surfaces, the only
gas-dependent parameter affecting the transfer velocity is the molecular
diffusivity of the transferring species. In contrast, bubble-mediated
transfer processes can cause the transfer velocity to depend on both
molecular diffusivity and aqueous-phase solubility. This can complicate
the analysis of data from dual-gaseous tracer gas transfer experiments.
Bubble effects also complicate the estimation of transfer velocities for
other gases from the transfer velocity calculated using the dual-tracer
data. Herein, a method for incorporating the effects of bubble-mediated
gas transfer processes on the transfer velocity is presented. This new
procedure is used to analyze the data from two recent dual-tracer gas
transfer experiments. Transfer velocities that include the effect of
bubbles are calculated using the data from two previous oceanic
dual-gaseous tracer experiments. Comparing these transfer velocities with
transfer velocities calculated by neglecting the effect of bubbles shows
that bubble-mediated transfer increased the transfer velocity of helium 3
by 5% at a wind speed of 10.6 m s-1. However, when using the transfer
velocities form helium 3 to calculate transfer velocities for carbon
dioxide under the same conditions, including the effect of bubbles,
decreases the transfer velocity of carbon dioxide by 18%. This shows that
bubble-mediated transfer does not have a large effect on the analysis of
dual-tracer data, but it is important in relating transfer velocities
determined using helium 3 and sulfur hexafluoride to transfer velocities
of more soluble gases at wind speeds above 10 m s-1.
AO-012
Asher, W., and R.H. WANNINKHOF. Transient tracers and air-sea gas
transfer. Journal of Geophysical Research, 103(C8):15,939-15,958 (1998).
This paper provides a review of the physics and chemistry associated with
air-sea gas transfer of transient atmospheric trace gases and the
available laboratory and field measurement techniques used to study
air-water gas transfer. The mechanistic principals and their relation to
the measurement techniques are used to show that the error associated
with estimating air-sea transfer velocities of transient tracers from
transfer velocities measured using proxy tracers can be significant if an
incorrect dependence of the transfer velocity on molecular diffusivity is
assumed. Bubble-mediated transfer processes are also demonstrated to have
a significant effect on the parameterization of the transfer velocity.
AO-013
BLACK, M.L., S.H. HOUSTON, and G. Carter. AFRES-NOAA flight-level data
comparisons. Minutes, 52nd Interdepartmental Hurricane Conference,
Clearwater, FL, January 26-30, 1998. Office of the Federal Coordinator
for Meteorological Services and Supporting Research, Washington, D.C.
(paper was mistakenly omitted from the Minutes) (1998).
A coordinated flight between an Air Force Reserve (AFRES) C-130 aircraft
and both National Oceanic and Atmospheric Administration (NOAA) WP-3D
aircraft was conducted on 12 July 1997. This mission was the third in
recent years and resulted from a recommendation made at the 49th
Interdepartmental Hurricane Conference. The AFRES and NOAA aircraft each
recorded, at 1-sec intervals, the standard suite of flight-level
meteorological data (winds, temperature, dew point, pressure) and
navigational information (e.g., position, true air speed, heading, etc.).
The data were collected during clear and moderate-wind conditions along
the Florida west coast, about 100 miles north of Tampa. The NOAA and
AFRES aircraft conducted "fly-bys" adjacent to an Air Force Aerostat
balloon which was carrying a NOAA calibrated instrument package. The
balloon approaches were at altitudes ranging from 1,000 to 10,000 feet
and provide the basis for the intercomparisons. A GPS dropwindsonde was
released along the coast to supply another set of independent
measurements. Comparisons between the flight-level data collected from
the balloon, the dropsonde, and the NOAA and AFRES aircraft will be
presented. Recommendations, if any, will be made to improve the data
collection, processing, and strategies for future intercomparison
flights. Additionally, the calibration information gained from this
flight will be used to investigate the data quality from concurrent
flights into tropical cyclones by both the NOAA and AFRES aircraft this
past hurricane season.
AO-014
BLACK, P.G., and L.K. Shay. Observations of tropical cyclone intensity
change due to air-sea interaction processes. Preprints, Symposium on
Tropical Cyclone Intensity Change, American Meteorological Society 78th
Annual Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological
Society, Boston, 161-168 (1998).
No abstract.
AO-015
BLACK, P.G., F.D. MARKS, P. DODGE, I. Popstefanija and R. Pauwl. First
observations from the vertically scanning Doppler radar (VSDR): A key to
G-IV reconnaissance operations. Minutes, 52nd Interdepartmental Hurricane
Conference, Clearwater, FL, January 26-30, 1998. Office of the Federal
Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A236-A256 (1998).
No abstract.
AO-016
Boebel, O., C. Duncombe Rae, S.L. GARZOLI, J. Lutjeharms, P. Richardson,
T. Rossby, C. SCHMID, and W. Zenk. Float experiment studies interocean
exchanges at the tip of Africa. EOS, Transactions, American Geophysical
Union, 79(1):7-8 (1998).
A joint research effort is currently focused on the oceanic region south
of Africa-the gateway for the exchange of mass, heat, and salt between
the Indian and Atlantic Oceans. The name of this collaboration, KAPEX,
stands for Cape of Good Hope Experiments, Kap der guten Hoffnung
Experimente, or Kap die Goeie Hoop Experimente in the three languages of
the participating scientists. This is the first time that scientists are
using acoustically tracked floats extensively in ocean regions
surrounding southern Africa to measure ocean flow patterns. At the tip of
Africa, the Agulhas Current from the Indian Ocean interacts with the
South Atlantic Current, contributing to the northwestward flowing
Benguela Current; which transports water, heat, and and salt to the
subtropical and subequatorial South Atlantic. This transport increases
the heat and salinity of the North Atlantic, preconditioning it for the
formation of the global thermohaline circulation cell, a driving force of
the world climate (Gordon et al., 1992). Our objective in the KAPEX is to
trace the flow of intermediate water around southern African by the
Agulhas, Benguela, and South Atlantic Current systems and to answer key
questions about the inter-oceanic intermediate circulation.
AO-017
Bosart, L.F., W.E. BRACKEN, J. Molinari, C.S. Velden, and P.G. BLACK.
Environmental influences on the rapid intensification stage of Hurricane
Opal (1995) over the Gulf of Mexico. Preprints, Symposium on Tropical
Cyclone Intensity Change, American Meteorological Society 78th Annual
Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological
Society, Boston, 105-112 (1998).
No abstract.
AO-017
Bosart, L.F., W.E. BRACKEN, J. Molinari, C.S. Velden, and P.G. BLACK.
Environmental influences on the rapid intensification stage of Hurricane
Opal (1995) over the Gulf of Mexico. Preprints, Symposium on Tropical
Cyclone Intensity Change, American Meteorological Society 78th Annual
Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological
Society, Boston, 105-112 (1998).
No abstract.
AO-018
Broecker, W.S., and T.-H. PENG. Greenhouse Puzzles, Part I, Keeling's
World: Is CO2 Greening the Earth? Eldigio Press, Lamont-Doherty Earth
Observatory of Columbia University, Palisades, New York, 111 pp. (1998).
This section's hero is Charles David Keeling. In the late 1950s, he had
the wisdom to establish two stations for the continuous precise
measurement of atmospheric carbon dioxide, one high on Hawaii's extinct
volcano Mauna Loa and the other at the South Pole. The records from these
stations provide the foundation upon which all studies of man's
perturbation of the Earth's carbon cycle rest. Not only did Keeling have
the foresight to establish these stations but also the tenacity to make
sure that year in and year out they produced accurate results. Keeling
took on this task as part of a career-long effort to understand the flux
of CO2 gas through the atmosphere, into the ocean and into and out of the
terrestrial biosphere. He was the first to realize the wealth of
information contained in the spatial and seasonal texture of the
atmosphere's CO2 content. In addition to his direct scientific
contribution, he fostered a secondary one. Son, Ralph, is doing for
atmospheric O2 all the kinds of things papa did for atmospheric CO2.
AO-019
Broecker, W.S., and T.-H. PENG. Greenhouse Puzzles, Part II, Martin's
World: CO2's Glacial Hideout? Eldigio Press, Lamont-Doherty Earth
Observatory of Columbia University, Palisades, New York, 73 pp. (1998).
The selection of the hero of this section has proven difficult. Under
consideration were those who first measured the low CO2 contents of air
trapped in glacial age ice, those who used carbon isotope ratios and
cadmium contents in foraminifera to set constraints on scenarios designed
to explain this drop, and those who demonstrated that the high latitude
outcrops of the deep sea dictated the CO2 content of the entire surface
ocean and, in turn, that of the atmosphere. But in the end, we initially
selected a dark horse, David Archer, who at the time this book was being
written, put his finger on what appeared to be the mechanism responsible
for the atmosphere's glacial to interglacial CO2 cycle. He obtained
microelectrode O2 and pH data from the upper few centimeters of deep sea
sediments which clearly demonstrated the importance of bacterial
respiration as a driver of calcite dissolution. Encouraged by preliminary
boron-isotope-based paleo pH measurements which suggested large deep sea
CO=3 concentrations during glacial time, Archer showed that an increase
in the rain rate of organic matter could generate the required CO=3 ion
change with little or no change in lysocline depth. But alas, now five
years later, Archer's hypothesis has like its predecessors fallen on hard
times. Danny Sigman, while a graduate student at Woods Hole, demonstrated
that the requisite large separation between the saturation horizon and
the lysocline could not be sustained. So in this second edition, we
replace David Archer with the late John Martin who pioneered the concept
that the availability of iron limits plant productivity in many parts of
the oceans. He also pointed out that the large excess of iron carried to
the sea during glacial time by the several-fold higher dust rain may have
been responsible for the CO2 drawdown.
AO-020
Broecker, W.S., and T.-H. PENG. Greenhouse Puzzles, Part III, Walker's
World: CO2, Chemical Traffic Controller? Eldigio Press, Lamont-Doherty
Earth Observatory of Columbia University, Palisades, New York, 93 pp. (1998).
This section's hero is James C.G. Walker, a space physicist at the
University of Michigan. In 1981, together with his colleagues P.B. Hays
and J.F. Kasting, he published a paper which lays out in beautiful
simplicity the role of atmospheric CO2 as the chemical policeman
controlling the flow of continental weathering products to the sea, and
thereby maintaining a balance between the rate of outgassing of CO2 gas
from our planet's interior and the rate of CO2 removal to sea floor
sediments as calcite. The important consequence of this police action is
its influence on Earth climate. Walker and his colleagues pointed out
that early in the Earth's history the tendency toward cooler temperatures
related to the faintness of the young Sun was mostly likely compensated
by higher atmospheric CO2 contents. In an attempt to explain the cooling
of the Earth over the last 100 million years, the role of Walker's
mechanism was subsequently expanded by Berner, Lasaga and Garrels, who
postulated that the cooling was driven by a decrease in the planetary
outgassing rate related to a progressive slowing of plate motions. This
suggestion was met with wide interest and became known as the BLAG
hypothesis in honor of its creators. In the enthusiasm to explore all the
aspects of BLAG, the earlier contribution of Walker tended to be
forgotten. Hopefully, in naming this section, we will help to return the
credit for the CO2 policing concept to its originator, James C.G. Walker.
AO-021
Broecker, W.S., S.L. Peacock, S. Walker, R. Weiss, E. Fahrbach, M.
Schroeder, U. Mikolajewicz, C. Heinze, R. Key, T.-H. PENG, and S. Rubin.
How much deep water is formed in the Southern Ocean? Journal of
Geophysical Research, 103(C8):15,833-15,843 (1998).
Three tracers are used to place constraints on the production rate of
ventilated deep water in the Southern Ocean. The distribution of the
water mass tracer PO4* ("phosphage star") in the deep sea suggests that
the amount of ventilated deep water produced in the Southern Ocean is
equal to or greater than the outflow of North Atlantic Deep Water from
the Atlantic. Radiocarbon distributions yield an export flux of water
from the North Atlantic which has averaged about 15 Sv over the last
several hundred years. CFC inventories are used as a direct indicator of
the current production rate of ventilated deep water in the Southern
Ocean. Although coverage is as yet sparse, it appears that the CFC
inventory is not inconsistent with the deep water production rate
required by the distributions of PO4* and radiocarbon. It has been
widely accepted that the major part of the deep water production in the
Southern Ocean takes place in the Weddell Sea. However, our estimate of
the Southern Ocean ventilated deep water flux is in conflict with
previous estimates of the flux of ventilated deep water from the Weddell
Sea, which lie in the range 1-5 Sv. Possible reasons for this difference
are discussed.
AO-022
CASTLE, R.D., R.H. WANNINKHOF, J.L. Bullister, S.C. Doney, R.A. Feely,
B.E. HUSS, E. JOHNS, F.J. Millero, K. LEE, D. Frazel, D. Wisegarver, D.
Greeley, F. Menzia, M. Lamb, G. BERBERIAN, and L.D. MOORE. Chemical and
hydrographic profiles and underway measurements from the eastern North
Atlantic during July and August of 1993. NOAA Data Report, ERL AOML-32
(PB98-131865), 82 pp. (1998).
From July 4-August 30, 1993, the National Oceanic and Atmospheric
Administration's (NOAA) Ocean-Atmosphere Carbon Exchange Study (OACES)
and Radiatively Important Trace Species (RITS) programs participated in
an oceanographic research cruise aboard the NOAA ship Malcolm Baldrige.
The objectives of the OACES component were to determine the source and
sink regions of CO2 in the equatorial and North Atlantic during the
summer and to establish a baseline of total carbon inventory in the
region. Data were collected from 5°S to Iceland along a nominal longitude
of 20°W. This report presents only the OACES-related data from legs 1,
2A, and 2B, including hydrography, nutrients, carbon species, dissolved
oxygen, total inorganic carbon, chlorofluorocarbons, total alkalinity,
pH, and salinity. Included are contour plots of the various parameters
and descriptions of the sampling techniques and analytical methods used
in data collection.
AO-023
Chelton, D.B., and A.M. MESTAS-NUÑEZ. The large-scale, wind-driven
response of the North Pacific. International WOCE Newsletter, 25:3-6 (1997).
In this note, we present the results of an investigation of the validity
of the time-varying Sverdrup balance in the North Pacific based on
analysis of three years of: (1) a simple flat bottom Sverdrup model; (2)
the primitive equation global ocean circulation model developed by the
Parallel Ocean Program (POP) at the Los Alamos National Laboratory; and
(3) observations of sea surface height (SSH) by the TOPEX/POSEIDON (T/P)
altimeter. The three-year period considered here is October 1992 through
November 1995. We conclude that much of the large-scale, low-frequency
variability in the North Pacific can be accounted for by simple Sverdrup
dynamics.
AO-024
Chen, G., B. Chapron, J. Tournadre, K.B. KATSAROS, and D. Vandemark.
Global oceanic precipitation: A joint view by TOPEX and the TOPEX
microwave radiometer. Journal of Geophysical Research,
102(C5):10,457-10,471 (1997).
The TOPEX/POSEIDEN mission offers the first opportunity to observe rain
cells over the ocean by a dual-frequency radar altimeter (TOPEX) and
simultaneously observe their natural radiative properties by a
three-frequency radiometer (TOPEX microwave radiometer (TMR)). This work
is a feasibility study aimed at understanding the capability and
potential of the active/passive TOPEX/TMR system for oceanic rainfall
detection. On the basis of past experiences in rain flagging, a joint
TOPEX/TMR rain probability index is proposed. This index integrates
several advantages of the two sensors and provides a more reliable rain
estimate than the radiometer alone. One year's TOPEX/TMR data are used
to test the performance of the index. The resulting rain frequency
statistics show quantitative agreement with those obtained from the
Comprehensive Ocean-Atmosphere Data Set (COADS) in the Intertropical
Convergence Zone (ITCZ), while qualitative agreement is found for other
regions of the world ocean. A recent finding that the latitudinal
frequency of precipitation over the Southern Ocean increases steadily
towards the Antarctic continent is confirmed by our result. Annual and
seasonal precipitation maps are derived from the index. Notable features
revealed include an overall similarity in rainfall pattern from the
Pacific, the Atlantic, and the Indian Oceans and a general phase reversal
between the two hemispheres, as well as a number of regional anomalies in
terms of rain intensity. Comparisons with simultaneous Global
Precipitation Climatology Project (GPCP) multisatellite precipitation
rates and COADS rain climatology suggest that systematic differences also
exist. One example is that the maximum rainfall in the ITCZ of the
Indian Ocean appears to be more intensive and concentrated in our result
compared to that of the GPCP. Another example is that the annual
precipitation produced by TOPEX/TMR is constantly higher than those from
GPCP and COADS in the extratropical regions of the northern hemisphere,
especially in the northwest Pacific Ocean. Analyses of the seasonal
variations of prominent rainy and dry zones in the tropics and subtropics
show various behaviors such as systematic migration, expansion, and
contraction, merging and breakup, and pure intensity variations. The
seasonality of regional features is largely influenced by local
atmospheric events such as monsoon, storm, or snow activities. The
results of this study suggest that TOPEX and its follow-on may serve as a
complementary sensor to the special sensor microwave/imager in observing
global oceanic precipitation.
AO-025
Chereskin, T.K., W.D. WILSON, H.L. Bryden, A. Ffield, and J. Morrison.
Observations of the Ekman balance at 8°30'N in the Arabian Sea during the
1995 southwest monsoon. Geophysical Research Letters, 24(21):2541-2544
(1997).
The Ekman transport is estimated from two sets of hydrographic and
shipboard acoustic Doppler current profiler (ADCP) velocity observations
made during June and September 1995, during the southwest monsoon in the
Arabian Sea. Both sets of measurements were made along latitude 8°30'N,
designated as World Ocean Circulation Experiment (WOCE) line I1W, from
Somalia to Sri Lanka. The Ekman transport estimates calculated from
ageostrophic velocity were southward: 17.6 ± 2.4 106 m3 s-1 in June and
7.9 ± 2.7 106 m3 s-1 in September. These direct estimates were in good
agreement with those predicted by the Ekman balance using both shipboard
and climatological winds. The vertical structure of the ageostrophic
velocity and the stratification were quite different between the two
occupations of the transect. The wind-driven momentum was confined to a
very shallow layer in June (about 50 m) and the surface layer was
strongly stratified, with a maximum salinity layer at depths between 50
and 70 m. The ageostrophic velocity penetrated much deeper in September
(to about 160 m) and the pycnocline was correspondingly deeper. In both
cases, the Ekman transport penetrated beneath the mixed layer, to the top
of the pycnocline.
AO-027
CIONE, J.J., S. Raman, L.J. Pietrafesa, R.A. Neuherz, K. Keeter, and X.
Li. The use of pre-storm low-level baroclinicity in determining and
implementing the Atlantic surface cyclone intensification index. Boundary
Layer Meteorology, 89:211-224 (1998).
The lateral motion of the Gulf Stream off the eastern seaboard of the
United States during the winter season can act to dramatically enhance
the low level baroclinicity within the coastal zone during periods of
offshore cold advection. The relative close proximity of the Gulf Stream
current off the mid-Atlantic coast can result in the rapid and intense
destabilization of the marine atmospheric boundary layer directly above
and shoreward of the Gulf Stream within this region. This airmass
modification period oftentimes precedes either wintertime coastal
cyclogenesis or the cyclonic re-development of existing mid-latitude
cyclones. A climatological study investigating the relationship between
the severity of the pre-storm, cold advective period, and subsequent
cyclogenic intensification was undertaken by Cione et al. in 1993.
Findings from this study illustrate that the thermal structure of the
continental airmass, as well as the position of the Gulf Stream front
relative to land during the pre-storm period (i.e., 24-48 h prior to the
initial cyclonic intensification), are linked to the observed rate of
surface cyclonic deepening for storms that either advected into or
initially developed within the Carolina-southeast Virginia offshore
coastal zone. It is a major objective of this research to test the
potential operational utility of this pre-storm low level baroclinic
linkage to subsequent cyclogenesis in an actual National Weather Service
(NWS) coastal winter storm forecast setting. The ability to produce
coastal surface cyclone intensity forecasts recently became available to
North Carolina State University researchers and NWS forecasters. This
statistical forecast guidance utilizes regression relationships derived
from a nine-season (January 1982- April 1990), 116-storm study conducted
by Cione et al. (1993). During the period between February 1994 and
February 1996, the Atlantic Surface Cyclone Intensification Index (ASCII)
was successfully implemented in an operational setting by the NWS at the
Raleigh-Durham forecast office for 10 winter storms. Analysis of these
ASCII forecasts will be presented.
AO-028
CRANE, M.L. Project ACCESS: Community coastal monitoring for year 2007.
Earth System Monitor, 8(4):12-16 (1998).
No abstract.
AO-029
Dietrich, D.E., C.A. Lin, A.M. MESTAS-NUÑEZ, and D.-S. Ko. A high
resolution numerical study of Gulf of Mexico fronts and eddies.
Meteorology and Atmospheric Physics, 64:187-201 (1997).
The Gulf of Mexico (GOM) circulation is simulated using the DieCAST ocean
model, with a horizontal resolution of 1/12 deg and 20 vertical layers.
The results compare well with observations of both large and small scale
features, including Loop Current frontal occlusions associated with
frontal eddies. The simulation is carried out without any data
assimilation. The frontal eddies tend to be spaced at about 90 deg
intervals around the Loop Current, leading to a Loop Current head shaped
like a square with rounded corners. The pattern rotates as eddies circle
the Loop, and frontal eddies elongate as they squeeze through the Florida
Strait. Major warm core eddies separate regularly from the Loop Current
and propagate to the western GOM. Old warm core eddies in the western
Gulf dissipate through bottom drag effects, which also generate cyclonic
parasitic eddies. Newly arrived warm core eddies merge with old ones in
the western GOM. Recently separated elongated Loop Current eddies can
rotate and reattach temporarily to the Loop Current. The barotropic flow
component develops eddies between the main separated warm core eddy and
the Loop Current due to eastward dispersion, as the main eddy itself
propagates westward into the Gulf.
AO-030
Donelan, M.A., W.M. Drennan, and K.B. KATSAROS. The air-sea momentum flux
conditions of wind sea and swell. Journal of Physical Oceanography,
27(10):2087-2099 (1997).
During the Surface Wave Dynamics Experiment, direct measurements of
momentum, heat, and water vapor fluxes were obtained from a mast on the
foredeck of a SWATH (small water-plane area, twin hull) ship in deep
water off the state of Virginia. Directional wave spectra were obtained
simultaneously from a six or three-wire wave-staff array mounted at the
bow of the ship. One hundred and twenty-six 17-minute runs of flux and
wave data obtained with the ship steaming slowly into the wind are
examined for the effects of the relative direction of the wind sea and
background swell on the momentum transfer. The adequacy of the inertial
dissipation method, which depends on the high-frequency turbulent
fluctuations for evaluating the wind stress, is also examined for any
effects of swell. The results show that the presence of counter- and
cross-swells can result in drag coefficients that are much larger than
the value for a pure wind sea. The eddy correlation and inertial
dissipation methods for measuring wind stress are found to diverge during
the complex sea conditions. The authors interpret the latter observations
as an indication that the traditional inertial dissipation method, in
which the pressure and transport terms in the kinetic energy balance
equation are assumed to be in balance, may be unsuitable for use in a
marine boundary layer disturbed by swell.
AO-031
Doney, S.C., J.L. Bullister, and R.H. WANNINKHOF. Climatic variability
in upper ocean ventilation rates diagnosed using chlorofluorocarbons.
Geophysical Research Letters, 25(9):1399-1402 (1998).
The chlorofluorocarbon CFC-12 (CCl2-F2) distributions from two
occupations of a meridional hydrographic section in the eastern North
Atlantic are used to describe the oceanic penetration of CFCs and change
in the integrated ventilation patterns over the five years from 1988 to
1993. The CFC-12 water-column inventories increased by 30-40%, despite a
slowing atmospheric growth rate (14%), because of continuing uptake by
undersaturated subsurface water masses whose response is lagged by the
ventilation time-scales. After removing the long-term CFC temporal trend
using a tracer age based normalization technique, we observe a distinct
dipole pattern in upper ocean ventilation, with reduced convection in the
subpolar gyre and enhanced production of saline subtropical underwater in
1993. These differences are discussed in relation to interannual
variability in atmospheric surface forcing, upper ocean anomalies, and
convection patterns associated with the North Atlantic Oscillation.
AO-032
Drennan, W.M., M.A. Donelan, E.A. Terray, and K.B. KATSAROS. On waves,
oceanic turbulence, and their interaction. Geophysica, 33:17-28 (1997).
No abstract.
AO-033
Dunion, J., S.H. HOUSTON, C. Velden, M.D. POWELL, and P.G. BLACK. Use of
GOES high-density low-level VIS winds to improve the estimation of
tropical cyclone outer wind radii. Minutes, 52nd Interdepartmental
Hurricane Conference, Clearwater, FL, January 26-30, 1998. Office of the
Federal Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A72-A87 (1998).
UW-CIMSS recently began providing real-time GOES low-level VIS winds in
the vicinity of tropical cyclones on a demonstrational basis to NOAA's
Hurricane Research Division (HRD). These data were included in many of
HRD's real-time tropical cyclone surface wind analyses which were sent
to NHC forecasters on an experimental basis during 1997. These wind
analyses are used as guidance in their tropical cyclone advisories and
warnings. The satellite observations provide essential coverage in the
periphery of hurricanes where conventional in-situ observations (e.g.,
ships, buoys, etc.) are often widely spaced or non-existent and
reconnaissance aircraft do not normally fly. The GOES VIS winds were
adjusted to the surface using a PBL model. These adjusted data were used
in real-time surface wind analyses for Hurricanes Danny and Erika of 1997
and were available for post-storm analyses in 1996 Hurricanes Edouard,
Fran, Hortense, and Lili. The satellite observations improved the
estimation of the 34 kt wind radii in many cases and also helped place
the 50 kt wind radii for some cases. Examples of the impact of these data
on hurricane surface wind analyses will be shown. Statistics on
comparisons (>100 cases) of the adjusted and unadjusted GOES VIS winds
with in-situ surface measurements will be presented. Also, in some cases
GPS-sonde profiles were available in the vicinity of the GOES VIS winds.
Comparisons of these highly detailed soundings with the satellite winds
and their height assignments will be shown. The potential for further
improvement of outer wind radii estimation through joint use of GOES VIS
winds and satellite-based scatterometer surface winds will be discussed.
AO-034
Dupuis, H., P.K. Taylor, A. Weill, and K.B. KATSAROS. Inertial
dissipation method applied to derive turbulent fluxes over the ocean
during the Surface of the Ocean, Fluxes, and Interactions with the
Atmosphere/Atlantic Stratocumulus Transition Experiment (SOFIA/ASTEX) and
Structure des Echanges Mer-Atmosphere, Propietes des Heterogeneites
Oceaniques: Recherche Experimentale (SEMAPHORE) experiments with low to
moderate wind speeds. Journal of Geophysical Research,
102(C9):21,115-21,129 (1997).
The transfer coefficients for momentum and heat have been determined for
10 m neutral wind speeds (U10n) between 0 and 12 m/s using data from the
Surface of the Ocean, Fluxes and Interactions with the Atmosphere (SOFIA)
and Structure des Echanges Mer-Atmosphere, Proprietes des Heterogeneites
Oceaniques: Recherche Experimentale (SEMAPHORE) experiments. The inertial
dissipation method was applied to wind and pseudo virtual temperature
spectra from a sonic anemometer, mounted on a platform (ship) which was
moving through the turbulence field. Under unstable conditions the
assumptions concerning the turbulent kinetic energy (TKE) budget appeared
incorrect. Using a bulk estimate for the stability parameter, Z/L (where
Z is the height and L is the Obukhov length), this resulted in
anomalously low drag coefficients compared to neutral conditions.
Determining Z/L iteratively, a low rate of convergence was achieved. It
was concluded that the divergence of the turbulent transport of TKE was
not negligible under unstable conditions. By minimizing the dependence of
the calculated neutral drag coefficient on stability, this term was
estimated at about -0.65 Z/L. The resulting turbulent fluxes were then in
close agreement with other studies at moderate wind speed. The drag and
exchange coefficients for low wind speeds were found to be Cen ´ 103 = +
0.66 (U10n < 5.2 m/s), Cen ´ 103 = Chn ´ 103 = 1.2 (U10n ³ 5.2 m/s), and
Cdn ´ 103 = + 0.668 (U10n < 5.5 m/s), which imply a rapid increase of
the coefficient values as the wind decreased within the smooth flow
regime. The frozen turbulence hypothesis and the assumptions of isotropy
and an inertial subrange were found to remain valid at these low wind
speeds for these shipboard measurements. Incorporation of a free
convection parameterization had little effect.
AO-035
Eads, L.J., H.A. FRIEDMAN, and D.J. Garcia. From humble beginnings as
the Inner City Marine Project to selection as a National School of
Excellence. Preprints, Seventh Symposium on Education, American
Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16,
1998. American Meteorological Society, Boston, 162-165 (1998).
The evolution of the MAST Academy (Maritime and Science Technology High
School), a Dade County Magnet School of Choice, from its predecessor, the
Inner City Marine Project (ICMP), is described. ICMP originated after
Dade County experienced civil unrest in the Black community in 1984. At
that time, Dr. Linda J. Eads, currently MAST Academy's principal, was
assigned to design a program in maritime education which emphasized
career exploration for minorities. The ICMP operated from the District
Office of the Dade County Public Schools and targeted elementary and
middle schools in the inner city with high minority populations. When
the MAST Academy opened its doors in 1991, the ICMP became the MAST
Academy Outreach Department which continued to provide programs for the
targeted schools. The MAST Academy presently carries on the tradition of
the ICMP by providing high school students with specialized marine-theme
science and technology courses. In 1996, the MAST Academy was selected
as a U.S. Department of Education National Blue Ribbon School of Excellence.
AO-036
Elfouhaily, T., B. Chapron, K.B. KATSAROS, and D. Vandemark. A unified
directional spectrum for long and short wind-driven waves. Journal of
Geophysical Research, 102(C7):15,781-15,796 (1997).
Review of several recent ocean surface wave models finds that while
comprehensive in many regards, these spectral models do not satisfy
certain additional, but fundamental, criteria. We propose that these
criteria include the ability to properly describe diverse fetch
conditions and to provide agreement with in-situ observations of Cox and
Munk (1954), Jahne and Riemer (1990), and Hara et al. (1994) data in the
high-wavenumber regime. Moreover, we find numerous analytically
undesirable aspects such as discontinuities across wavenumber limits,
nonphysical tuning or adjustment parameters, and noncentrosymmetric
directional spreading functions. This paper describes a two-dimensional
wavenumber spectrum valid over all wavenumbers and analytically amenable
to usage in electromagnetic models. The two regime model is formulated
based on the Joint North Sea Wave Project (JONSWAP) in the long-wave
regime and on the work of Phillips (1985) and Kitaigorodskii (1973) at
the high wavenumbers. The omnidirectional and wind-dependent spectrum is
constructed to agree with past and recent observations including the
criteria mentioned above. The key feature of this model is the similarity
of description for the high- and low-wavenumber regimes; both forms are
posed to stress that the air-sea interaction process of friction between
wind and waves (i.e., generalized wave age, u/c) is occurring at all
wavelengths simultaneously. This wave age parameterization is the
unifying feature of the spectrum. The spectrum's directional spreading
function is symmetric about the wind direction and has both wavenumber
and wind speed dependence. A ratio method is described that enables
comparison of this spreading function with previous noncentrosymmetric
forms. Radar data are purposefully excluded from this spectral
development. Finally, a test of the spectrum is made by deriving
roughness length using the boundary layer model of Kitaigorodskii. Our
inference of drag coefficient versus wind speed and wave age shows
encouraging agreement with Humidity Exchange Over the Sea (HEXOS)
campaign results.
AO-037
Ellis, G., P. Swart, M. Lutz, C. Alvarez-Zarikian, P. Blackwelder, T.A.
NELSEN, H. Wanless, and J. Trefry. The stable isotope composition of
foraminifera, ostracods, and organic material in a dated core from
Whitewater Bay. Proceedings, 1998 Florida Bay Science Conference, Miami,
Florida, May 12-14, 1998. Florida Sea Grant College, 2 pp. (1998).
No abstract.
AO-038
Ellsberry, R.L., and F.D. MARKS. U.S. Weather Research Program Hurricane
Landfall Workshop Report. Technical Note, NCAR/TN-442, 40 pp. (1998).
No abstract.
AO-038
Ellsberry, R.L., and F.D. MARKS. U.S. Weather Research Program Hurricane
Landfall Workshop Report. Technical Note, NCAR/TN-442, 40 pp. (1998).
No abstract.
AO-039
Feely, R.A., R.H. WANNINKHOF, C. Goyet, D.E. Archer, and T. Takahashi.
Variability of CO2 distributions and sea-air fluxes in the central and
eastern equatorial Pacific during the 1991-1994 El Niño. Deep-Sea
Research II, 44(9-10):1851-1867 (1997).
As part of the U.S. JGOFS Program and the NOAA Ocean-Atmosphere Carbon
Exchange Study (OACES), measurements of CO2 partial pressure were made in
the atmosphere and in the surface waters of the central and eastern
equatorial Pacific during the boreal spring and autumn of 1992, the
spring of 1993, and the spring and autumn of 1994. Surface-water pCO2
data indicate significant diurnal, seasonal, and interannual variations.
The largest variations were associated with the 1991-1994 ENSO event,
which reached maximum intensity in the spring of 1992. The lower values
of surface-water DpCO2 observed during the 1991-1994 ENSO period were the
result of the combined effects of both remotely and locally forced
physical processes. The warm pool, which reached a maximum eastward
extent in January-February of 1992, began in September of 1991 as a
series of westerly wind events lasting about 30 days. Each wind event
initiated an eastward-propagating Kelvin wave which caused a deepening of
the thermocline. By the end of January 1992 the thermocline was at its
maximum depth, so that the upwelled water was warm and CO2-depleted. In
April of the same year, the local winds were weaker than normal, and the
upwelling was from shallow depths. These changes resulted in a
lower-than-normal CO2 flux to the atmosphere. The results show that for
the one-year period from the fall of 1991 until the fall of 1992,
approximately 0.3 GtC were released to the atmosphere; 0.6 GtC were
released in 1993, and 0.7 GtC in 1994, in good agreement with the model
results of Ciais et al. (Science, 269, 1098-1102; J. Geophys. Res., 100,
5051-5070). The net reduction of the ocean-atmosphere CO2 flux during the
1991-1994 El Niño was on the order of 0.8-1.2 GtC. Thus, the total amount
of CO2 sequestered in the equatorial oceans during the prolonged
1991-1994 El Niño period was about 25% higher than the severe El Niño of
1982-1983.
AO-040
Feely, R.A., R.H. WANNINKHOF, H.B. Milburn, C.E. Cosca, M. Stapp, and
P.P. Murphy. A new automated underway system for making high precision
pCO2 measurements onboard ships of opportunity. Analytica Chimica Acta,
377:185-191 (1998).
We have developed a new temperature-controlled, automated underway system
for making atmospheric and surface ocean pCO2 measurements onboard
research vessels equipped with an uncontaminated seawater intake system.
Uncontaminated seawater is supplied to a showerhead plexiglass
equilibrator at the rate of approximately 50 liters/minute. After about 3
minutes, the air trapped in the equilibrator is equilibrated with
seawater. This air is sampled six times per hour. In addition,
atmospheric air is sampled three times per hour from the intake on the
bow flagstaff through 3/8" DekabonÔ tubing to the underway system. The
CO2 measurements are made with a differential, non-dispersive, infrared
analyzer LiCorÔ (model 6252). The underway system operates on an hourly
cycle with the first quarter of each hour devoted to calibration with
three CO2 standards, each measured for 5 minutes. A second order
polynomial calibration curve is calculated from the voltage values of the
standards. The remaining time in each hour is used to measure
equilibrator air (15 min), bow air (15 min), and equilibrator air once
again (15 min). To date, we have successfully used the underway pCO2
system on 12 cruises of the NOAA Ship Ka'imimoana in the equatorial
Pacific. The analytical precision of the system is approximately 0.3-0.4
ppm for seawater and for air.
AO-041
Ffield, A., J. Toole, and W.D. WILSON. Seasonal circulation in the South
Indian Ocean. Geophysical Research Letters, 24(22):2773-2776 (1997).
Two World Ocean Circulation Experiment hydrographic cruises in March and
June 1995, along with Topex-Poseidon altimeter data and National
Meteorological Center wind data, are used to estimate seasonal changes in
the South Indian Ocean subtropical gyre. Mean annual curves derived from
the altimeter and wind data reveal strengthening of the anticyclonic gyre
in March and September, and weakening in June and December. The seasonal
changes correspond to variations in the wind field south of 30°S at the
equinoxes and solstices. In addition, the wind-driven gyre is further
north in July, and further south in March. These variations in strength
and location of the South Indian Ocean gyre may influence inter-ocean
transports south of Africa. Despite the inferred mean annual seasonal
variations in the South Indian Ocean gyre, volume transports estimated in
1995 from the hydrographic data are close to mean values. Apparently, a
mesoscale eddy in March disrupts the stronger fall gyre, whereas in June
the weaker winter gyre is delayed by 1 month.
AO-042
Ffield, A., C.I. FLEURANT, R.L. MOLINARI, and W.D. WILSON. NOAA Ship
Malcolm Baldrige 1995 cruises: MB95-02, MB95-04, MB95-07 hydrographic
data. LDEO-98-1, Technical Report, 310 pp. (1998).
No abstract.
AO-043
FRANKLIN, J.L., and M.L. BLACK. GPS dropwindsonde data in hurricanes.
Minutes, 52nd Interdepartmental Hurricane Conference, Clearwater, FL,
January 26-30, 1998. Office of the Federal Coordinator for
Meteorological Services and Supporting Research, Washington, D.C.,
A111-A142 (1998).
The 1997 hurricane season was the first with both NOAA WP-3D aircraft
equipped with the new NCAR GPS dropwindsonde system. The GPS sonde
replaces the old Omega-based ODW, in use since the early 80's on the
P-3s. During the season, the first successful dropwindsonde releases (of
any kind) were made in a hurricane eyewall (Guillermo). These were
followed by additional eyewall releases in Hurricane Erika. The wind
profiles show that surface winds in the eyewall may be much higher than
what is typically inferred from flight-level reconnaissance data. Very
strong jets resolved by the GPS dropsondes in and just above the boundary
layer may be indicative of peak surface gusts.
AO-044
FRIEDMAN, H.A., and D.J. Garcia. Tropical cyclone public awareness
programmes: Preparing for the twenty-first century. Preprints, Seventh
Symposium on Education, American Meteorological Society 78th Annual
Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological
Society, Boston, 166-168 (1998).
During the period from 1969 to 1993, a total of 1551 tropical cyclones,
typhoons, and hurricanes occurred worldwide. Literally millions of lives
are affected each year, and billions of dollars are lost as a result of
these storms. At present, we can do little, if anything, to lessen the
occurrence, frequency, or intensity of tropical cyclones, or to influence
their paths. But over the past three decades, significant advances have
been made in mankind's capability to prepare for and mitigate their
damaging effects. Concerted international scientific efforts have
resulted in better understanding the phenomenon of tropical cyclones,
their formation, characteristics, path of movement, and effects.
Technical advances in weather monitoring equipment-satellites, computers,
improved radar systems, and other space age meteorological tools-enable
scientists today to vigilantly monitor cyclones as they form, track them
as they move, and predict with some accuracy where they are likely to
impact on land and people. Correspondingly, meteorological services in
many countries have been substantially improved in recent years. Cyclone
monitoring equipment has been installed in most cyclone-prone regions of
the world. National systems have been linked to regional and
international networks through which meteorological data is shared and
warnings of approaching cyclones conveyed. In many localities, local
communication systems and administrative procedures have been
strengthened to ensure that information about approaching cyclones is
passed to communities most at risk. While great strides have been made in
our ability to understand and live with cyclones, still more must be
done. We must strive to further expand our basic knowledge about tropical
cyclones, upgrade tools needed for weather monitoring and prediction,
improve the warning and communi-ca-tions network, and strengthen
meteorological services. It is a useful reminder that the primary
objectives of these varied activities is to prevent the loss of lives and
prevent or minimize property damage from cyclones. The need for continued
effort is reconfirmed by the deaths and destruction left in the wake of
each tropical cyclone that affects populated areas today; a problem that
is likely to continue and increase in seriousness as coastal populations
enlarge. The goal of preventing loss of life and reducing property
damage from tropical cyclones, however, can not be achieved simply
through improved technical and meteorological services. Accurate
prediction and timely notice are critically important, but loss of life
and property can only be minimized if officials and the general public
are knowledgeable of the hazards faced, understand the warnings provided,
and take the proper actions to protect life and property before, during,
and after a cyclone. The process required to achieve a public state of
readiness is commonly referred to as an awareness program. A resource
guide, designed to provide a framework for the development and
implementation of local tropical cyclone awareness programs, will be
discussed. The Internet was used extensively to obtain up-to-date
information on worldwide issues concerning tropical cyclones. The guide's
design encourages interactive use by disaster preparedness officials and
educators at the local level. Questionnaires and community-specific
checklists are provided to elicit local participation in the process of
creating tropical cyclone awareness.
AO-045
Garcia, D.J., H.A. FRIEDMAN, and L.J. Eads. MAST Academy outreach:
Serving the community with marine theme programs. Preprints, Seventh
Symposium on Education, American Meteorological Society 78th Annual
Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological
Society, Boston, 169-171 (1998).
The MAST Academy's Outreach Department provides marine theme enrichment
programs which emphasize career opportunities for targeted schools with
high minority enrollments. Enrichment programs include the Land SHARC
(Science Hands-on and Related Careers) and WOW (Weather On Wheels) mobile
laboratories, environmental field trips, internships, and the MAST
Mariners Program, a middle school summer course focused on, but not
exclusively for, minority students. The role of NOAA's Atlantic
Oceanographic and Meteorological Laboratory (AOML) and other outside
agencies in providing school year and summer internships for MAST Academy
students is discussed. Meteorologists from AOML's Hurricane Research
Division serve as advisory board members for the WOW; their contributions
to the program are presented.
AO-046
German, C.R., D.L. Bourles, E.T. Brown, J. Hergt, S. Colley, N.C. Higgs,
E.M. Ludford, T.A. NELSEN, R.A. Feely, G. Raisbeck, and F. Yiou.
Hydrothermal scavenging on the Juan de Fuca Ridge: 230Thxs, 10Be, and REE
in ridge-flank sediments. Geochimica et Cosmochimica Acta,
61(19):4067-4078 (1997).
We have investigated the geochemistry of a hydrothermally-enriched
sediment core recovered from the western flank of the N. Cleft Segment,
Juan de Fuca Ridge, 8 km west of the "MegaPlume" area previously
identified near 45°N. The core contains varying biogenic, lithogenic, and
hydrothermal components, as reflected in CaCO3, Al, and Fe contents,
respectively. Horizons of pronounced hydrothermal input, in core-top
sediments and at depth, exhibit increased concentrations of Fe, Cu, Zn,
Pb, and shifts in Pb isotopic compositions toward nonradiogenic
(MORB/hydrothermal) values. REE concentrations co-vary with hydrothermal
Fe down-core, and shale-normalized REE distributions patterns exhibit
both negative Ce-anomalies and positive Eu-anomalies, indicative of input
from plume-particle fall-out. Unsupported 230Thxs activities down-core
are consistent with continuous slow sediment accumulation rates of 0.54
cm/ky for 200 ky since the deposition of the deeper Fe-rich horizon.
10Be(0) and 9Be isotope concentrations also co-vary with hydrothermal Fe
down-core and exhibit 10Be(0) 9Be ratios which approach that of Pacific
Ocean deep water, indicative of a seawater-scavenging source. 10Be(0)
230Thxs(0) ratios throughout most of Core GC88-6 are greater than mean
Pacific Ocean values, indicating that hydrothermal scavenging can lead to
significant net removal of dissolved 10Be into ridge-flank sediments.
AO-047
Gordon, A.L., S. Ma, D.B. Olson, P. Hacker, A. Ffield, L.D. Talley, W.D.
WILSON, and M.O. BARINGER. Advection and diffusion of Indonesian
throughflow within the Indian Ocean South Equatorial Current.
Geophysical Research Letters, 24(21):2573-2576 (1997).
Warm, low salinity Pacific water weaves through the Indonesian Seas into
the eastern boundary of the Indian Ocean. The Indonesian Throughflow
Water (ITW) adds freshwater into the Indian Ocean as it spreads by the
advection and diffusion within the Indian Ocean's South Equatorial
Current (SEC). The low salinity throughflow trace, centered along 12°S,
stretches across the Indian Ocean, separating the monsoon-dominated
regime of the northern Indian Ocean from the more typical subtropical
stratification to the south. ITW is well represented within the SEC
thermocline, extending with concentrations above 80% of initial
characteristics from the sea surface to 300-m within the eastern half of
the Indian Ocean, with 60% concentration reaching well into the western
Indian Ocean. The ITW transport within the SEC varies from 4 to 12 ´ 106
m3 sec-1, partly in response to variations of the injection rate at the
eastern boundary and to the likelihood of a zonally elongated
recirculation cell between the Equatorial Counter Current and the SEC
within the Indian Ocean. Lateral mixing disperses the ITW plume
meridionally with an effective isopycnal mixing coefficient of 1.1 to 1.6
´ 104 m2 sec-1.
AO-048
HANSEN, D.V., and M.S. SWENSON. Application of oceanic heat budgets to
evaluation of surface heat flux climatologies. Proceedings, First
International Conference on Reanalyses, Washington, D.C., October 27-31,
1997. World Climate Research Programme, 40 (1998).
We are using the extensive WOCE/TOGA data sets from drifting buoys and
VOS/XBT measurements for quantification of climatological heat budget
processes in the equatorial cold tongue and NECC regions of the eastern
tropical Pacific Ocean. One interesting application of the results is in
their implication for the net surface heat flux. Early results suggest
that the heat flux climatology generated from the NCEP/NCAR Reanalysis
Project is superior to other popular climatologies. A major factor in the
improvement appears to be the annual cycle of downward shortwave radiation.
AO-049
HENDEE, J.C. An expert system for marine environmental monitoring in the
Florida Keys National Marine Sanctuary and Florida Bay. Proceedings, 2nd
International Conference on the Coastal Environment, Cancun, Mexico,
September 8-10, 1998. Computational Mechanics Publications/WIT Press,
Southampton, 57-66 (1998).
The National Oceanic and Atmospheric Administration's (NOAA, U.S.
Department of Commerce) Atlantic Oceanographic and Meteorological
Laboratory (AOML) works cooperatively with the Florida Institute of
Oceanography (FIO) in the implementation of the SEAKEYS (Sustained
Ecological Research Related to Management of the Florida Keys Seascape)
network, which is situated along 220 miles of coral reef tract within the
Florida Keys National Marine Sanctuary (FKNMS). This network is itself
actually an enhanced framework of seven Coastal-Marine Automated Network
(C-MAN) stations for long-term monitoring of meteorological parameters
(wind speed, wind gusts, air temperature, barometric pressure, relative
humidity). To the C-MAN network, SEAKEYS adds oceanographic parameters
(sea temperature, photosynthetically active radiation, salinity,
fluorometry, optical density) to the stations. As a recent enhancement
to the SEAKEYS network, an expert system shell is being employed to
provide daily interpretations of near real-time acquired data for the
benefit of scientists, fishermen, and skin divers. These interpretations
are designed to be automatically emailed to Sanctuary managers and to the
FIO maintainers of the network. The first set of interpretations include
those dealing with environmental conditions conducive to coral bleaching.
Other marine environmental interpretations will be forthcoming.
AO-050
Henderson-Sellers, A., H. Zhang, G. Berz, K. Emanuel, W. Gray, C.W.
LANDSEA, G. Holland, J. Lighthill, S.-L. Shieh, P. Webster, and K.
McGuffie. Tropical cyclones and global climate change: A post-IPCC
assessment. Bulletin of the American Meteorological Society, 79(1):19-38
(1998).
The very limited instrumental record makes extensive analyses of the
natural variability of global tropical cyclone activities difficult in
most of the tropical cyclone basins. However, in the two regions where
reasonably reliable records exist (the North Atlantic and the western
North Pacific), substantial multidecadal variability (particularly for
intense Atlantic hurricanes) is found, but there is no clear evidence of
long-term trends. Efforts have been initiated to use geological and
geomorphological records and analysis of oxygen isotope ratios in
rainfall recorded in cave stalactites to establish a paleoclimate of
tropical cyclones, but these have not yet produced definitive results.
Recent thermo-dynamical estimation of the maximum potential intensities
(MPI) of tropical cyclones shows good agreement with observations.
Although there are some uncertainties in these MPI approaches, such as
their sensitivity to variations in parameters and failure to include some
potentially important interactions such as ocean spray feedbacks, the
response of upper-oceanic thermal structure and eye and eyewall dynamics
do appear to be an objective tool with which to predict present and
future maxima of tropical cyclone intensity. Recent studies indicate the
MPI of cyclones will remain the same or undergo a modest increase of up
to 10%-20%. These predicted changes are small compared with the observed
natural variations and fall within the uncertainty range in current
studies. Furthermore, the known omissions (ocean spray, momentum
restriction, and possibly also surface to 300-hPa lapse rate changes)
could all operate to mitigate the predicted intensification. A strong
caveat must be placed on analysis of results from current GCM simulations
of the "tropical-cyclone-like" vortices. Their realism, and hence
prediction skills (and also that of "embedded" mesoscale models), is
greatly limited by the coarse resolution of current GCMs and the failure
to capture environmental factors that govern cyclone intensity. Little,
therefore, can be said about the potential changes of the distribution of
intensities as opposed to maximum achievable intensity. Current knowledge
and available techniques are too rudimentary for quantitative indications
of potential changes in tropical cyclone frequency. The broad geographic
regions of cyclogenesis and, therefore, also the regions affected by
tropical cyclones are not expected to change significantly. It is
emphasized that the popular belief that the region of cyclogenesis will
expand with the 26°C SST isotherm is a fallacy. The very modest available
evidence points to an expectation of little or no change in global
frequency. Regional and local frequencies could change substantially in
either direction, because of the dependence of cyclone genesis and track
on other phenomena (e.g., ENSO) that are not yet predictable. Greatly
improved skills from coupled global ocean-atmosphere models are required
before improved predictions are possible.
AO-051
Hitchcock, G., G.A. Vargo, T. Lee, E. JOHNS, E. Williams, and J. Jurado.
The influence of circulation on nutrient distributions in western Florida
Bay. Proceedings, 1998 Florida Bay Science Conference, Miami, Florida,
May 12-14, 1998. Florida Sea Grant College Program, 98-99 (1998).
No abstract.
AO-052
Hood, T., C. Alvarez-Zarikian, P. Blackwelder, P. Swart, T.A. NELSEN,
H.R. Wanless, J.H. Trefry, and L. Tedesco. The sediment record as a
monitor of natural and anthropogenic changes in the lower
Everglades/Florida Bay ecosystem. Proceedings, 1998 Florida Bay Science
Conference, Miami, Florida, May 12-14, 1998. Florida Sea Grant College
Program, 33-34 (1998).
No abstract.
AO-053
HOUSTON, S.H., and M.D. POWELL. Reconstruction of surface wind fields
for hurricanes affecting Florida Bay. Preprints, Second Conference on
Coastal Atmospheric and Oceanic Prediction and Processes, American
Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16,
1998. American Meteorological Society, Boston, 241-244 (1998).
Hurricanes constitute episodic events which affect the physical and
oceanographic processes within Florida Bay. These effects are manifested
by significant changes in water-levels, waves, currents, and sediment
transport processes. In addition, these storms impact plant and animal
life in the Bay and the surrounding areas. Hurricane wind fields are now
being made available to researchers, such as oceanographers and
biologists, on a Hurricane Research Division World Wide Web site
(http://www.aoml.noaa.gov/hrd). Researchers can use the wind fields to
estimate the potential impacts of future tropical cyclones on the south
Florida ecosystem and especially on Florida Bay. The hurricanes used in
this study were the Labor Day Hurricane of 1935, Donna of 1960, Betsy of
1965, Felix of 1987, and Andrew of 1992. These tropical cyclones
represented vastly different scenarios for the type of event that might
be expected over extreme south Florida. The 1935 hurricane was a
category 5 storm and is the most intense hurricane known to have struck
the USA. This hurricane had a relatively small, concentrated wind field
when it crossed the Florida Keys and Florida Bay. Hurricane Donna (1960)
was a category 4 hurricane with a much broader wind field that crossed
the Keys and Bay on a similar track to the 1935 Hurricane. Hurricane
Andrew was a fast moving category 4 hurricane when it struck south
Florida recently. However, its strongest winds covered only a very small
area, especially to the south of the storm track. The direct impact of
Andrew on Florida Bay appears to have been minimal, but decomposing
organic storm debris in the Everglades likely contributed to water
quality problems in the Bay.
AO-054
HOUSTON, S.H., and M.D. POWELL. Surface wind field in Florida Bay
hurricanes. Proceedings, 1998 Florida Bay Science Conference, Miami,
Florida, May 12-14, 1998. Florida Sea Grant College Program, 35 (1998).
No abstract.
AO-055
HOUSTON, S.H., and M.D. POWELL. Surface wind fields in hurricanes.
Proceedings, Third International Symposium, Waves '97, Virginia Beach,
VA, November 3-7, 1997. American Society of Civil Engineers, 1391-1399
(1998).
No abstract.
AO-056
HOUSTON, S.H., and M. D. POWELL. The potential impact of GPS sondes in
real-time surface wind analyses for hurricanes. Minutes, 52nd
Interdepartmental Hurricane Conference, Clearwater, FL, January 26-30,
1998. Office of the Federal Coordinator for Meteorological Services and
Supporting Research, Washington, D.C., A-110 (1998).
During the 1996 and 1997 hurricane seasons, GPS sondes were dropped
within the inner core of some tropical cyclones (i.e., Josephine of 1996;
Danny, Erika, Guillermo, and Linda of 1997). The data from these sondes
provided some highly detailed boundary layer profiles and surface
measurements of each tropical cyclone's wind and thermodynamic properties
after the fact. During the upcoming 1998 hurricane season, two potential
developments may make the GPS sonde data useful for defining the
hurricane's surface wind structure in real-time: (1) The GPS sonde "temp
drop message" sent from AFRES and NOAA missions in and near hurricanes
(including drops from the NOAA G-IV) may include additional essential
information that will likely enhance the real-time use of these sondes.
For example, the splash location and time are two additional parameters
that may be available in the drop messages. (2) When it is deemed
necessary by NHC for the issuance of warnings and (or) other critical
factors, GPS sondes may be dropped along the flight-track of tasked
reconnaissance flights. These drops have the potential to provide
estimates of the peak surface winds and may help define some of the wind
radii (i.e., 34, 50, and/or 64 kt wind radii) in those quadrants where
the drops are made. This study examines the potential impacts additional
wind and thermodynamic observations from sondes might have on surface
wind analyses in hurricanes, which are currently provided to NHC's
forecasters in real-time by HRD on an experimental basis. Some examples
of post-storm analyses in 1997 hurricanes utilizing these new data in
addition to conventional data sources will be presented and the potential
impacts will be assessed. In addition, some preliminary comparisons of
the boundary layer measurements from GPS sondes with reliable in-situ
surface observations (e.g., buoys, C-MAN's, etc.) of wind, temperature,
and pressure in the vicinity of tropical cyclones will be shown.
AO-057
HOUSTON, S.H., M. Lawrence, S. Spisak, and S. MURILLO. A verification of
National Hurricane Center forecasts of surface wind speed radii in
hurricanes. Preprints, Symposium on Tropical Cyclone Intensity Change,
American Meteorological Society 78th Annual Meeting, Phoenix, AZ, January
11-16, 1998. American Meteorological Society, Boston, 139-140 (1998).
The National Hurricane Center (NHC) issues a position and intensity
forecast every six hours on all tropical cyclones in the Atlantic and
eastern Pacific basins. This forecast is contained in the
forecast/advisory product and includes a forecast of the horizontal
distribution of the surface wind field. This distribution is given as
radii in four quadrants from the center of the tropical cyclone to three
wind speed values: 17.5, 25.7, and 32.9 m s-1 (i.e., 34, 50, and 64 kt,
respectively). A set of opportunistic marine observations were collected
to determine the wind speed radii from the center of each tropical
cyclone to the observation site. This can be done when a tropical
cyclone's wind field affects a measurement platform with the required
wind speeds. The wind speed radii based on the marine platform data were
used to verify the official NHC radii forecasts described above. The
preliminary results are for 17.5 m s-1 wind speeds and are based on only
25 cases. Statistics will be presented showing that the mean absolute
error of the 25 cases of verification is about 83 km (45 nm) at the
initial (i.e., 0 h) forecast period and decreases about 25% by the 36 h
forecast. There is a positive bias (the forecasts were larger than
observed) of about 37 km (20 nm) for these cases, which also appears to
decrease with longer forecast periods. The small number of cases limits
our analysis to simple averages. This is the first time that such a data
set has been prepared and that forecasts of tropical cyclone intensity in
terms of wind speed radii have been verified. Details on the method of
verification will be given along with the final statistics of the study,
including 17.5 and 25.7 m s-1 radii verification.
AO-058
Huang, H., R.E. Fergen, J.R. PRONI, and J.J. TSAI. Initial dilution
equations for buoyancy-dominated jets in currents. Journal of Hydraulic
Engineering, 124:105-108 (1998).
Initial dilution of submerged, single, round, buoyancy-dominated jets in
a current is considered. Two simple semi-empirical equations, one for
centerline dilution and the other for minimum surface dilution, are
presented. These equations are derived based on the continuity equation
for the buoyant jet flow with a hypothesis that shear entrainment and
forced entrainment can be added. Available laboratory and field data are
used to determine the constants in the equations. Unlike asymptotic
equations which apply for the limiting flow regimes, the proposed
equations span all flow regimes, from the buoyancy-dominated near field
(BDNF), to the transition, and to the buoyancy-dominated far field
(BDFF), providing continuous predictions for dilutions.
AO-059
Humphrey, J.C., T.C. Moore, J.C. HENDEE, and J.C. Ogden. SEAKEYS:
Real-time monitoring of the Florida Keys reef tract and Florida Bay.
28th Meeting Association of Marine Laboratories of the Caribbean
(ALMC-97), San Pedro, Costa Rica, July 21-25, 1997. University of Costa
Rica, 51 (1997).
No abstract.
AO-060
Jameson, A.R., A.B. Kostinski, and R.A. BLACK. The texture of clouds.
Journal of Geophysical Research-Atmospheres, 103(D6):6211-6220 (1998).
Using a precise definition of clustering, it is shown that in two
tropical cumulus clouds, droplets appear to be bunched over distances
ranging from at least a kilometer or more down to several centimeters. A
statistical framework is proposed for quantifying clustering in terms of
a Poisson probability mixture. While these observations require further
substantiation in many different clouds, droplet clustering may play a
role in diverse phenomena from the coalescence growth of raindrops to the
scattering of radiation by clouds.
AO-061
JOHNS, E., and W.D. WILSON. Direct observations of velocity structure in
the passages between the Intra-Americas Sea and the Atlantic Ocean,
1984-1996. Proceedings, Conference on the Transports and Linkages of the
Intra-Americas Sea (IAS), Cozumel, Mexico, November 1-5, 1997.
IOC/IOCARIBE/MMS, 36 (1998).
Shipboard acoustic Doppler current profiler (ADCP) velocity data
collected between 1984 and 1996 in connection with several NOAA research
programs have been used to examine the mean and variability of the
velocity structure within the Straits of Florida, the Northwest
Providence Channel, a northern approach to the Windward Passage, the Mona
and Anegada Passages, and across the eastern Caribbean Sea. Historically,
direct velocity data collection in these important passages between the
Gulf of Mexico, the Caribbean Sea, and the Atlantic Ocean has been very
sparse. Herein, we examine the transport and velocity structure in the
passages using a more complete data set than previously available. This
newer data set allows computation of statistically significant mean and
standard deviations of the transport and velocity fields, and examination
of the temporal (seasonal to interannual) variability of these fields.
Comparison will be made of the mean and varying flow fields with the
results of previous studies and with available time series of regional
forcing functions such as the COADS wind stress data set. Most
importantly, the mean transports should prove useful to numerical
modelers of the Intra-Americas Sea for calibration and refinement of
model boundary conditions.
AO-062
JOHNS, E., R.A. Fine, and R.L. MOLINARI. Deep flow along the western
boundary south of the Blake Bahama Outer Ridge. Journal of Physical
Oceanography, 27(10):2187-2208 (1997).
In June-July 1990, hydrographic, chloroflourocarbon (CFC), and direct
velocity observations were taken in the western North Atlantic between
the Blake Bahama Outer Ridge (BBOR) at 30°N and San Salvador Island at
24°N. The deep flow in the region, dominated by the Deep Western
Boundary Current (DWBC), forms a pattern of strong, narrow currents and
cyclonic gyres close to the continental slope, with broad, weaker
southward flow offshore. The CFCs reveal that in general the most
recently ventilated water (i.e., having the highest CFC concentrations)
is found along the western boundary as two distinct cores within the DWBC
between potential temperatures 4-6°C and 1.9-2.4°C. Geostrophic
transport streamlines are constructed for the DWBC layers, referenced
using direct velocity observations at 26.5°N and assuming mass
conservation between closed areas bounded by the hydrographic sections.
The tracers and transports are used to define the spatial scales and
strengths of the recirculation gyres and to examine their relationship to
bottom topography and their role in ventilating the interior. Geostrophic
transports for the DWBC layers which transit the region and continue
equatorward along the western boundary are approximately 5 Sv for the
4-6°C layer; 14 Sv for the 2.4-4.0°C layer; 9 Sv for the 1.9-2.4°C layer;
and 3 Sv below 1.9°C, for a total equatorward DWBC transport of 31 Sv
below 6°C. A cyclonic gyre with one or more embedded gyres extends out
to about 74°W, transporting 12 Sv of water intermediate CFC
concentrations. Farther offshore, a broad band of southward flow
contributes an additional 16 Sv of water with lower CFC concentration to
the total equatorward transport. This flow may be connected to a much
larger elongated cyclonic recirculation gyre which reaches equatorward to
the Guiana Basin off northeastern Brazil. The close correspondence of
the tracer distributions with the regional topography indicates that the
major topographic features in this region strongly influence the
circulation, particularly in the deep and bottom layers. It appears that
the most recently ventilated water, between 4-6°C and 1.9-2.4°C, does not
reach the southern top of the BBOR, but rather it bypasses the BBOR to
the north of the study region and turns back westward following the
isobaths toward the western boundary north of 30°N. Only in the coldest
layer (<1.9°C) are the relatively highest CFCs observed south of 30°N on
the BBOR. The layer containing the shallow CFC core (4-6°C) is
apparently less constrained by the bottom topography; 3 Sv are carried
westward across the axis of the BBOR forming an extended zonal high CFC
and salinity distribution related to the Gulf Stream recirculation.
South of the BBOR, due to the steep topography west of the Blake Basin,
the DWBC is channeled into a narrow equatorward boundary flow. At the
San Salvador Spur, some of the more recently ventilated water appears to
be deflected northward following the isobaths in a cyclonic gyre around
the extension of the Bahama Ridge. The cyclonic gyres between the BBOR
and the San Salvador Spur appear to be localized features close to the
western boundary that may have little impact on the larger-scale deep
North Atlantic circulation. Nevertheless, the gyres serve to ventilate
the interior by diluting the tracer concentration carried equatorward by
the DWBC.
AO-063
JOHNS, E., W.D. WILSON, and T.N. Lee. Interaction of Florida Bay waters
with the Gulf of Mexico and the Atlantic Ocean. Proceedings, 1998
Meeting of the Oceanography Society and the Intergovernmental
Oceanographic Commission on Coastal and Marginal Seas, Paris, France,
June 1-4, 1998. Oceanography, 11, No. 2 supplement, 38 (1998).
As part of the South Florida Ecosystem Restoration program, an
observational study of the circulation of Florida Bay and its connection
with the surrounding waters of the Gulf of Mexico, the southwest Florida
shelf, and the Atlantic Ocean is presently underway. Measurement systems
include moored arrays equipped with current meters, bottom pressure
sensors and conductivity-temperature sensors, satellite-tracked surface
drifters, and shipboard ADCP. Bimonthly interdisciplinary surveys include
continuous thermosalinograph observations of surface salinity,
temperature, and fluorescence. Early results show that there is a net
southeastward flow of 1 to 4 cm/s which transports waters from the Gulf
of Mexico and the Everglades across western Florida Bay and through the
channels of the Florida Keys, on a time scale of 1 to 3 months depending
on local wind forcing. This net flow, with a volume transport of 1000 to
2000 m3/s, has the potential to deliver harmful algal blooms and excess
nutrients out to the environmentally sensitive coral reefs of the Florida
Keys National Marine Sanctuary. The ongoing study now focuses on refining
and quantifying the flow between the Gulf of Mexico, Florida Bay, and the
Atlantic and its response to seasonal and episodic meteorological
forcing. In addition, new emphasis is placed on examining the fate of the
freshwater river discharges from the Everglades into the Gulf of Mexico,
and the relation of the river plume dispersion to regional wind and
rainfall distributions.
AO-064
KAPLAN, J., and M. DeMaria. Climatological and synoptic characteristics
of rapidly intensifying tropical cyclones in the North Atlantic basin.
Preprints, Symposiuim on Tropical Cyclone Intensity Change, American
Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16,
1998. American Meteorological Society, Boston, 119-123 (1998).
No abstract.
AO-065
KATSAROS, K.B. Turbulent flux of water vapor in relation to the wave
field and atmospheric stratification. In Physical Processes in Lakes and
Oceans, J. Imberger (ed.). Coastal and Estuarine Studies, Volume 54,
American Geophysical Union, 37-46 (1998).
Field measurements of evaporation rate, momentum, and heat flux together
with mean meteorological quantities allow inferences to be drawn
concerning the sheltering of air in the troughs of large waves and the
possible differences between moisture and heat fluxes in very stable
regimes over water. Interpretation of the measurements in terms of the
processes near the surface are based on the Monin-Obukhov similarity
theory. The results presented indicate that in the presence of water
waves and under strong atmospheric stable stratification further detailed
measurements are needed to fully explain the processes at work and that
Monin-Obukhov theory may need modification.
AO-066
Knaff, J.A, and C.W. LANDSEA. An El Niño-Southern Oscillation CLImatology
and PERsistence (CLIPER) forecasting scheme. Weather and Forecasting,
12(3):633-652 (1997).
A statistical prediction method, which is based entirely on the optimal
combination of persistence, month-to-month trend of initial conditions,
and climatology, is developed for the El Niño-Southern Oscillation (ENSO)
phenomena. The selection of predictors is by design intended to avoid any
pretense of predictive ability based on "model physics" and the like, but
rather is to specify the optimal "no-skill" forecast as a baseline
comparison for more sophisticated forecast methods. Multiple least
squares regression using the method of leaps and bounds is employed to
test a total of 14 possible predictors for the selection of the best
predictors, based upon 1950-1994 developmental data. A range of zero to
four predictors were chosen in developing 12 separate regression models,
developed separately for each initial calendar month. The predictands to
be forecast include the Southern Oscillation (pressure) index (SOI) and
the Niño 1+2, Niño 3, Niño 4, and Niño 3.4 SST indices for the equatorial
eastern and central Pacific at lead times ranging from zero seasons (0-2
months) through seven seasons (21-23 months). Though hindcast ability is
strongly seasonally dependent, substantial improvement is achieved over
simple persistence wherein largest gains occur for two-seven-season (6-23
months) lead times. For example, expected maximum forecast ability for
the Niño 3.4 SST region, depending on the initial date, reaches 92%, 85%,
64%, 41%, 36%, 24%, 24%, and 28% of variance for leads of zero to seven
seasons. Comparable maxima of persistence only forecasts explain 92%,
77%, 50%, 17%, 6%, 14%, 21%, and 17%, respectively. More sophisticated
statistical and dynamic forecasting models are encouraged to utilize this
ENSO-CLIPER model in place of persistence when assessing whether they
have achieved forecasting skill; to this end, real-time results for this
model are made available via a Web site.
AO-067
LANDSEA, C.W. Comments on "Will greenhouse gas-induced warming over the
next 50 years lead to higher frequency and greater intensity of
hurricanes. Tellus A, 49(5):622-623 (1997).
No abstract.
AO-068
LANDSEA, C.W., and R.A. Pielke. Trends in U.S. hurricane losses, 1925
1995. Preprints, Ninth Symposium on Global Change Studies, American
Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16,
1998. American Meteorological Society, Boston, 210-212 (1998).
No abstract.
AO-069
LANDSEA, C.W., J. KAPLAN, and M. DeMaria. The differing roles of the
large-scale environment in the intensity changes of recent Atlantic
hurricanes. Preprints, Symposium on Tropical Cyclone Intensity Change,
American Meteorological Society 78th Annual Meeting, Phoenix, AZ, January
11-16, 1998. American Meteorological Society, Boston, 113-114 (1998).
No abstract.
AO-070
LANDSEA, C.W., N. Nicholls, and J. Gill. Australian region tropical
cyclones: Recent trend and interannual predictions. Preprints, Ninth
Conference on Interaction of the Sea and Atmosphere, American
Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16,
1998. American Meteorological Society, Boston, 1-4 (1998).
No abstract.
AO-071
LANDSEA, C.W., G.D. Bell, W.M. Gray, and S.B. GOLDENBERG. The extremely
active 1995 Atlantic hurricane season: Environmental conditions and
verification of seasonal forecasts. Monthly Weather Review,
126(5):1174-1193 (1998).
The 1995 Atlantic hurricane season was a year of near-record hurricane
activity with a total of 19 named storms (average is 9.3 for the base
period 1950-1990) and 11 hurricanes (average is 5.8), which persisted for
a total of 121 named storm days (average is 46.6) and 60 hurricane days
(average is 23.9), respectively. There were five intense (or major)
Saffir-Simpson category 3, 4, or 5 hurricanes (average is 2.3 intense
hurricanes) with 11.75 intense hurricane days (average is 4.7). The net
tropical cyclone activity, based upon the combined values of named
storms, hurricanes, intense hurricanes and their days present, was 229%
of the average. Additionally, 1995 saw the return of hurricane activity
to the deep tropical latitudes: seven hurricanes developed south of 25°N
(excluding all of the Gulf of Mexico) compared with just one during all
of 1991-1994. Interestingly, all seven storms that formed south of 20°N
in August and September recurved to the northeast without making landfall
in the United States. The sharply increased hurricane activity during
1995 is attributed to the juxtaposition of virtually all of the
large-scale features over the tropical North Atlantic that favor tropical
cyclogenesis and development. These include extremely low vertical wind
shear, below-normal sea level pressure, abnormally warm ocean waters,
higher than average amounts of total precipitable water, and a strong
west phase of the stratospheric quasi-biennial oscillation. These
various environmental factors were in strong contrast to those of the
very unfavorable conditions that accompanied the extremely quiet 1994
hurricane season. The favorable conditions for the 1995 hurricane season
began to develop as far back as the previous winter. Their onset well
ahead of the start of the hurricane season indicates that they are a
cause of the increased hurricane activity, and not an effect. The extreme
duration of the atmospheric circulation anomalies over the tropical North
Atlantic is partly attributed to a transition in the equatorial Pacific
from warm episode conditions (El Niño) to cold episode conditions (La
Niña) prior to the onset of the hurricane season. Though the season as a
whole was extremely active, 1995's Atlantic tropical cyclogenesis showed
a strong intraseasonal variability with above-normal storm frequency
during August and October and below normal for September. This
variability is likely attributed to changes in the upper-tropospheric
circulation across the tropical North Atlantic, which resulted in a
return to near-normal vertical shear during September. Another
contributing factor to the reduction in tropical cyclogenesis during
September may have been a temporary return to the near-normal SSTs across
the tropical and subtropical North Atlantic, caused by the enhanced
tropical cyclone activity during August. Seasonal hurricane forecasts for
1995 issued at Colorado State University on 30 November 1994, 5 June
1995, and 4 August 1995 correctly anticipated an above-average season,
but underforecast the extent of the extreme hurricane activity.
AO-072
LANDSEA, C.W., N. Nicholls, W.M. Gray, and L.A. Avilla. Reply to Comment
by R.W. Wilson on "Downward trend in the frequency of intense Atlantic
hurricanes during the past five decades." Geophysical Research Letters,
24(17):2205-2206 (1997).
No abstract.
AO-073
LANDSEA, C.W., W.M. Gray, J.A. Knaff, P.W. Mielke, and K.J. Berry.
Verification of the 1997 seasonal hurricane forecast and a prediction for
1998. Minutes, 52nd Interdepartmental Hurricane Conference, Clearwater,
FL, January 27, 1998. Office of the Federal Coordinator for
Meteorological Services and Supporting Research, Washington, D.C.,
A-331-A-338 (1998).
The forecast for the 1998 Atlantic hurricane season issued by Dr. Bill
Gray and collaborators (including myself) will be discussed. This
prediction, to be issued in early December 1997, will be updated in early
April, early June, and early August. Uncertainties in the predictors,
especially in El Niño, Atlantic sea surface temperatures, and Sahel
rainfall, will be discussed in how they may impact the number and
intensity of tropical cyclones this year. I will also analyze and
discuss the performance of the 1997 forecasts.
AO-074
LEE, K., and W.M. Sackett. The high temperature titration of biogenic
silica. Deep-Sea Research I, 45(6):1015-1028 (1998).
A new method has been developed for measuring biogenic silica (amorphous)
in marine sediments. It is based on the Högbom-Urey reaction CaCO3+SiO2
(biogenic silica)->CaSiO3 (wollastonite)+CO2. The reaction is carried out
in evacuated sealed glass tubes with added excess reagent grade calcite
at 500°C for 3 d. The product CO2 is measured in a calibrated manometer.
The dependence of the reaction on time, temperature, product CO2
pressure, and other factors is examined.
AO-075
Lee, T.N., E. JOHNS, W.D. WILSON, and E. Williams. Florida Bay
circulation and exchange study. Proceedings, 1998 Florida Bay Science
Conference, Miami, Florida, May 12-14, 1998. Florida Sea Grant College
Program, 43-44 (1998).
No abstract.
AO-076
MARKS, F.D., and H.A. FRIEDMAN. 1998 Hurricane Field Program Plan. U.S.
Department of Commerce, NOAA/Atlantic Oceanographic and Meteorological
Laboratory, Miami, Florida (published for limited distribution), 144 pp.
(1998).
The objective of the National Oceanic and Atmospheric Administration
(NOAA) hurricane research field program is the collection of descriptive
data that are required to support analytical and theoretical hurricane
studies. These studies are designed to improve the understanding of the
structure and behavior of hurricanes. The ultimate purpose is to develop
improved methods of hurricane prediction. Ten major experiments have
been planned, by principal investigators at the Hurricane Research
Division (HRD)/Atlantic Oceanographic and Meteorological Laboratory
(AOML) of NOAA and the Mission Planning Committee for the National
Aeronautics and Space Administration (NASA) Third Convection and Moisture
Experiment (CAMEX-3), for the 1998 Hurricane Field Program. These
experiments will be conducted with the NOAA/Aircraft Operations Center
(AOC) WP-3D and Gulfstream IV-SP aircraft and the NASA DC-8 and ER-2
aircraft.
AO-077
MARKS, F.D., and L.K. Shay. Landfalling tropical cyclones: Forecast
problems and associated research opportunities. Preprints, 16th
Conference on Weather Analysis and Forecasting, Symposium on the Research
Foci of the U.S. Weather Research Program, American Meteorological
Society 78th Annual Meeting, Phoenix, AZ, January 11-16, 1998. American
Meteorological Society, Boston, 520-523 (1998).
No abstract.
AO-078
MARKS, F.D., L.K. Shay, and PDT-5 (Fifth Prospectus Development Team).
Landfalling tropical cyclones: Forecast problems and associated research
opportunities. Report of the Fifth Prospectus Development Team to the
U.S. Weather Research Program. Bulletin of the American Meteorological
Society, 79(8):305-323 (1998).
The Fifth Prospectus Development Team of the U.S. Weather Research
Program was charged to identify and delineate emerging research
opportunities relevant to the prediction of local weather, flooding, and
coastal ocean currents associated with landfalling U.S. hurricanes
specifically, and tropical cyclones in general. Central to this theme
are basic and applied research topics, including rapid intensity change,
initialization of and parameterization in dynamical models, coupling of
atmospheric and oceanic models, quantitative use of satellite
information, and mobile observing strategies to acquire observations to
evaluate and validate predictive models. To improve the necessary
understanding of physical processes and provide the initial conditions
for realistic predictions, a focused, comprehensive mobile observing
system in a translating storm-coordinate system is required. Given the
development of proven instrumentation and improvement of existing
systems, three-dimensional atmospheric and oceanic data sets need to be
acquired whenever major hurricanes threaten the United States. The
spatial context of these focused three-dimensional data sets over the
storm scales is provided by satellites, aircraft, expendable probes
released from aircraft, and coastal (both fixed and mobile), moored, and
drifting surface platforms. To take full advantage of these new
observations, techniques need to be developed to objectively analyze
these observations, and initialize models aimed at improving prediction
of hurricane track and intensity from global-scale to mesoscale dynamical
models. Multinested models allow prediction of all scales from the
global, which determine long-term hurricane motion to the convective
scale, which affect intensity. Development of an integrated analysis and
model forecast system optimizing the use of three-dimensional
observations and providing the necessary forecast skill on all relevant
spatial scales is required. Detailed diagnostic analyses of these data
sets will lead to improved understanding of the physical processes of
hurricane motion, intensity change, the atmospheric and oceanic boundary
layers, and the air-sea coupling mechanisms. The ultimate aim of this
effort is the construction of real-time analyses of storm surge, winds,
and rain, prior to and during landfall, to improve warnings and provide
local officials with the comprehensive information required for recovery
efforts in the hardest hit areas as quickly as possible.
AO-079
MASTERS, J.C., R.H. WANNINKHOF, D.T. Ho, M. Steckley, R.A. Feely, and C.
Cosca. Continuous air and surface seawater measurements of fCO2 on board
the NOAA ship Malcolm Baldrige around-the-world cruise in 1995. NOAA
Data Report, ERL AOML-31 (PB98-105950), 65 pp. (1997).
From February 1995 through January 1996 the NOAA ship Malcolm Baldrige
conducted scientific operations on an around-the-world tour. The
majority of work occurred in the Indian Ocean. The CO2 groups of the
National Oceanic and Atmospheric Administration's (NOAA) Atlantic
Oceanographic and Meteorological Laboratory (AOML) and Pacific Marine
Environmental Laboratory (PMEL) operated a continuously flowing partial
pressure carbon dioxide analyzer. Samples were taken from both the
surface water and the overlying atmosphere to determine carbon dioxide
flux across the gas/water interface. Other parameters such as salinity,
barometric pressure, and temperature were used to reduce the data and
calculate the fugacity of CO2*. Total dissolved inorganic carbon (DIC)
samples of surface water were also collected. Data were collected on
each leg of the cruise. Leg 1 was a transit from Miami to Durban, South
Africa. Leg 2 operated from Durban to Colombo, Sri Lanka. Leg 3
operated from Colombo to Muscat, Oman. Leg 4 operated from Muscat to
Victoria, Seychelles. Leg 5 operated from Victoria to Muscat, Oman. Leg
6 operated from Muscat to Diego Garcia. Leg 7 consisted of a transit
from Diego Garcia to Fremantle, Australia followed by the major
scientific operations between Fremantle and Male, Maldive Islands. Leg 8
included another transit from Male to Darwin, Australia. Operations began
after leaving Darwin and headed into the western equatorial Pacific. The
ship inported in American Samoa and continued to Panama, Miami, Florida
and finished in Charleston, South Carolina. Descriptions of sampling
methods and graphical data summaries are given in this report.
AO-080
MAYER, D.A., and R.H. Weisberg. El Niño-Southern Oscillation related
ocean-atmosphere coupling in the western equatorial Pacific. Journal of
Geophysical Research, 103(C9):18,635-18,648 (1998).
Using 43 years of Comprehensive Ocean-Atmosphere Data Set (COADS) and
related data for the period 1950-1992, an examination is made into the
regional dependence of ocean-atmosphere coupling in relation to the El
Niño-Southern Oscillation (ENSO). The cross correlation between sea
surface temperature (SST) and sea level pressure (SLP) anomalies over the
global tropics shows two patterns of significant negative correlation
consistent with a local hydrostatic response of SLP to SST: (1) the
eastern Pacific, where the correlation is symmetric about and largest on
the equator; and (2) the western Pacific, where symmetric regions of
negative correlation are found off the equator, separated by a region of
positive correlation on the equator. Anomalies within these two patterns
vary out of phase with each other. While the SLP anomalies on both sides
of the basin are of similar magnitude, the SST anomalies in the east are
much larger than those in the west. Despite this disparity in the SST
anomaly magnitudes between the eastern and western Pacific, we argue that
the ocean-atmosphere couplings in the western and west-central Pacific
are important for ENSO. The off-equator SST anomalies in the west enhance
the SLP anomalies there and they appear to initiate easterly wind
anomalies over the far western Pacific during the peak El Niño phase of
ENSO. As these easterlies evolve, their effect upon the ocean tends to
oppose that of the westerly wind anomalies found over the west-central
Pacific. These competing effects suggest a mechanism that may contribute
to coupled ocean-atmosphere system oscillations. The west-central
equatorial Pacific (the region separating the eastern and western
patterns), while exhibiting large momentum and heat flux exchanges, shows
minimum correlation between SST and SLP. Thus, neither the SST and SLP
anomaly magnitudes nor the correlation between them are alone indicative
of ocean-atmosphere coupling, and the regional dependence for such
coupling in relation to ENSO appears more complicated than mechanistic
interpretations of ENSO would suggest.
AO-081
MAYER, D.A., R.L. MOLINARI, and J.F. FESTA. The mean and annual cycle of
upper layer temperature fields in relation to Sverdrup dynamics within
the gyres of the Atlantic Ocean. Journal of Geophysical Research,
103(C9):18,545-18,566 (1998).
Using 28 years of expendable bathythermograph data (1967-1994), we
describe the mean and annual cycle of the upper ocean temperature fields
in the Atlantic from 30°S to 50°N in the context of the basin-scale
wind-driven gyres (Sverdrup stream function field) which provide a
framework for describing the oceanographic measurements. We examine the
circulation field implied by the temperature distributions which are used
as a proxy for the field of mass. Similarities between the temperature
and stream function fields increase with depth. In the lower to
subthermocline depths of the tropical and equatorial gyres, the zonal
currents form a closed circulation. A Southeastward Boundary Current is
suggested near and below 150 m that provides closure for the tropical
gyre, and the equatorial gyre axis is southward of that suggested by the
stream function field. Higher in the water column, the North Equatorial
Countercurrent (NECC) may be a surface manifestation of the North
Equatorial Undercurrent (NEUC) where the latter can be interpreted as the
southern limb of the tropical gyre. Because there are large vertical
shears in the tropics, the equatorial gyre is not clearly indicated in
the vertically integrated temperature field but appears below about 200
m. Here, the South Equatorial Undercurrent (SEUC) can be interpreted as
the eastward flowing northern limb of the equatorial gyre and is opposite
in direction to the westward flowing South Equatorial Current above. Both
the NEUC and SEUC are analagous to currents in the Pacific that are
governed by non-Sverdrup dynamics. Despite the shortcomings of the data,
the mean annual cycle appears to be relatively stable, and we have
discounted the possibility that in regions where it represents a
significant percentage of the total variance, it is changing slowly over
the 28 years of record. The wind-forcing fields, which undergo large
meridional movements (5-6 of latitude) during their annual cycle, with
some exceptions, have essentially no counterpart in gyre movements
between their seasonal extremes. Most of the variability associated with
the annual cycle is confined to the upper 300 m. Greatest variability,
where ranges exceed 6°C, occurs in the northwestern Atlantic in late
winter and early spring. During this time of year south of the Gulf
Stream and below about 100 m, water temperatures exhibit a systematic
phase lag with depth. The next largest area of variability, where ranges
can also exceed 6°C, resides in the tropical western basin between the
equator and 10°N just below 100 m. In the eastern basin, ranges decrease
and shoal. Additionally, the phase fields are consistent with the
intensification and relaxation of the tropical ridge-trough system where
the NECC disappears in March in the west but the NECC/NEUC complex is
strongest in September.
AO-082
MAYER, D.A., G.J. GOÑI, M.O. BARINGER, and R. L. MOLINARI. Comparison of
hydrographic and altimetric estimates of sea level height variability in
the Atlantic Ocean. EOS, Transactions, American Geophysical Union,
79(45):F432 (1998).
Hydrographic estimates of dynamic height (DH) derived from expendable
bathythermograph (XBT) data and average temperature salinity (TS)
relationships are compared to sea height anomalies (SHA) derived from
TOPEX/Poseidon (T/P) altimeter data along two sections of the Atlantic
Ocean. Our inquiry examines the relationship between the variability of
dynamic effects in the upper 500 m of the water column and SHA over
seasonal to interannual time scales for the period 1993 through 1997. Our
spatial domain extends from 30°S to 50°N. Emphasis is on two well sampled
sections representative of the western and eastern regions of the
Atlantic. Both the XBT and T/P data are matched by time and location
within 2° of latitude by 4° of longitude quadrangles and then binned by
month. The SHA signal is compared to DH derived with respect to reference
depths ranging from 50 m to 500 m. DH is estimated from T/P data by
computing their linear correlations along both sections. The subtropics
show correlations that remain relatively constant throughout most of the
water column. This reveals the dominant effects of seasonal heating on
SHA due to surface fluxes. In contrast, correlations in the tropics can
be sharply depth dependent, suggesting the effects of ocean dynamics
(thermocline depth) on SHA due to the seasonal cycle of the zonal
currents and their system of ridges and troughs. Correlations are
generally significant at the 90% significance level (SL). With a few
exceptions, most of the relationship between SHA and DH is a consequence
of the annual cycle. Correlations degrade well below the 90% SL if the
annual cycle is removed before the correlations are computed. In both the
tropics and subtropics, most of the dynamic height signal can be
accounted for by using reference depths of 500 m. However, the DH does
not fully account for the SHA by a factor of 2 or more in some instances.
This discrepancy can be attributed to factors such as the use of average
historical TS relationships, the spatial averaging within each 2° by 4°
quadrangle, reference depths to only 500 m, and barotropic effects.
AO-083
McCarthy, M.C., L.D. Talley, and M.O. BARINGER. Deep upwelling and
diffusivity in the southern Central Indian Basin. Geophysical Research
Letters, 24(22):2801-2804 (1997).
Transport of the deepest water westward through a gap at 28°S in the
NinetyEast Ridge between the Central Indian Basin and the West Australia
Basin is calculated from hydrographic data collected as part of the WOCE
Hydrographic Program section I8N. Zero reference velocity levels at
mid-depth were chosen through consideration of water masses. The small
transport of 1.0 Sv westward through the gap of water denser than s4 =
45.92 kg/m3 must all upwell in the southern Central Indian Basin. Of
this, 0.7 Sv upwells between the central and western sill sections, that
is, close to the sill itself. Using the areas covered by the isopycnal,
we calculate an average vertical velocity of 3.3 ´ 10-3 cm/s close to the
sill and of 4.2 ´ 10-4 cm/s west of the sill. Associated average vertical
diffusivities are 105 cm2/s close to the sill and 13 cm2/s west of the
sill, in this very near bottom layer.
AO-084
McElligott, S., R.H. Byrne, K. LEE, R.H. WANNINKHOF, F.J. Millero, and
R.A. Feely. Discrete water column measurements of CO2 fugacity and pHT
in seawater: A comparison of direct measurements and thermodynamic
calculations. Marine Chemistry, 60(1-2):63-73 (1998).
The NOAA equatorial Pacific CO2 system data set (»2500 water samples) has
been evaluated to assess the internal consistency of measurements and
calculations involving CO2 fugacity and pHT. This assessment represents
the first large scale field comparison of pHT and fCO2 data. Comparisons
of direct discrete CO2 fugacity (fCO2) measurements with CO2 fugacity
calculated from total inorganic carbon (CT), total alkalinity (AT), and
spectrophotometric pH (pHT = -log[H+]T) indicate that a variety of
improvements are needed in the parameter measurements and thermodynamic
relationships used to relate fCO2 , CT, AT, and pHT in seawater. CO2
fugacity calculated from CT and pHT or AT and pHT agree with direct
measurements to no better than 1%. Comparisons of measured fugacity, fCO2
(measured), and CO2 fugacity calculated from CT and pHT, fCO2 (CT, pHT),
indicate that the precision of fCO2 calculations is good relative to
direct measurements. In contrast, due to the extreme sensitivity of fCO2
and [H+]T calculations to relatively small errors in both CT and AT, CO2
fugacity, as well as [H+]T, calculated from CT and AT are very imprecise
and render comparisons with direct measurements of little use.
Consequently, precise calculations of fCO2 require the use of direct pHT
measurements.
AO-085
McLeish, W., D.V. HANSEN, and J.R. PRONI. Coastal currents induced by
Hurricane Andrew. Florida Scientist, 60(4):254-264 (1997).
Ocean current meters in 18 and 24 m depth water along the southeast
Florida coast recorded water motions as Hurricane Andrew crossed the
narrow continental shelf with the storm center 32 km from the
southernmost current meter. Wind speeds up to 48 m s-1 at the meter
closest to the storm path were associated with recorded mean current
speeds up to 94 cm s-1. The greatest water speeds, however, were
transient motions from the wind waves. These motions caused major
changes to the bottom and to objects lying on it. Direct and remotely
sensed observations showed an increasing degree of turbulence in the
water as the hurricane approached, stirring both air bubbles and bottom
sediment throughout the water and mixing the water so that vertical shear
in the current was suppressed. Thus, beneath the strong wind stress
there was not a mean water flow in the direction of the wind at the
surface and a flow in the opposite direction near the bottom, as had been
indicated in previous studies. Some of the water that had been forced
toward shore by the strong west moving wind in the hurricane eyewall
moved northward along the coast. In a region where the wind speed was
less but still of hurricane force, water was displaced offshore contrary
to the direction of the wind stress. At the same time that the offshore
current developed, wave motions became much more severe: it appears that
the new countercurrent may have induced major hurricane waves to break in
this farther offshore location.
AO-086
Mielke, P.W., K.J. Berry, C.W. LANDSEA, and W.M. Gray. A single-sample
estimate of shrinkage in meteorological forecasting. Weather and
Forecasting, 12(4):847-858 (1997).
An estimator of shrinkage based on information contained in a single
sample is presented and the results of a simulation study are reported.
The effects of sample size, amount, and severity of nonrepresentative
data in the population, inclusion of noninformative predictors, and least
(sum of) absolute deviations and least (sum of) squared deviations
regression models are examined on the estimator. A single-sample
estimator of shrinkage based on drop-one cross-validation is shown to be
highly accurate under a wide variety of research conditions.
AO-087
Millero, F.J., and J.-Z. ZHANG. Adsorption of phosphate on calcium
carbonate. Proceedings, 1998 Florida Bay Science Conference, Miami,
Florida, May 12-14, 1998. Florida Sea Grant College Program, 115 (1998).
No abstract.
AO-088
Millero, F.J., K. LEE, and M. Roche. Distribution of alkalinity in the
surface waters of the major oceans. Marine Chemistry, 60(1-2):111-130 (1998).
In recent years the total alkalinity (TA) of seawater has been measured
with high precision (~ ±2 mmol kg-1) in the Atlantic, Pacific, and Indian
oceans. In this paper, we have analyzed the surface alkalinity of the
major ocean basins using these measurements as well as those obtained
during the GEOSECS and TTO studies. The salinity normalized alkalinity
(NTA=TA ´ 35/S) in subtropical gyres between 30°S and 30°N is remarkably
invariable except in upwelling areas (e.g., the eastern equatorial
Pacific). The NTA increases toward high latitudes (>40°) and is inversely
proportional to sea surface temperature (SST). This increase in NTA with
latitude (or decreasing temperature) is attributed to the upward
transport of deep waters with higher NTA due to the dissolution of
CaCO3(s). The distribution of surface NTA in the major ocean basins shows
that the major basins can be divided into regions where different trends
of NTA are observed and boundaries between the regions are similar to
those of the major ocean currents. The linear behavior of NTA (~ ±5 mmol
kg-1) with respect to SST makes it possible to provide regional maps of
NTA. These maps can be used to estimate TA in surface waters in large
areas of the ocean from values of SST and salinity (S). By combining the
estimates of TA using SST and S (from the Climatological Atlas of the
World Ocean) with underway fCO2 measurements (by ships, moorings, and
satellites), it is possible to map the detailed distribution of TCO2 for
surface waters over a large area of the ocean. Calculations of TCO2 from
measurements of fCO2, SST, and S in the subtropical Pacific Ocean agree
with the coulometrically measured values to ±5 mmol kg-1.
AO-089
Millero, F.J., W. Yao, K. LEE, J.-Z. ZHANG, and D.M. Campbell. Carbonate
system in the waters near the Galapagos Islands. Deep-Sea Research II,
45(6):1115-1134 (1998).
During the IRONEX cruise in the equatorial Pacific Ocean, the carbonate
parameters TA (total alkalinity), TCO2 (total inorganic carbon), pH, and
fCO2 (fugacity of CO2), were determined both in a small (8 ´ 8 km) patch
of water fertilized with Fe and in the waters around the Galapagos
Islands. The CO2 parameters, along with hydrographic properties, were
found to be uniform in the surface waters of the study area before the
addition of iron. A significant decrease of the surface TCO2 (7 mmol
kg-1) and fCO2 (11 matm) in the patch was detected within 48 h of the
iron release. This decrease, however, did not continue and was lower
than expected from the complete utilization of NO3- due to the addition
of iron. The shipboard iron addition experiments (3 nM fe) resulted in a
continual decrease of TCO2 (up to 48 mmol kg-1) and complete consumption
of the nutrients. A good correlation was found between TCO2, pH, and fCO2
with temperature in the surface waters around the Galapagos Islands. The
salinity (S = 35) normalized alkalinities were quite uniform (NTA = 2310
± 9 mol kg-1) throughout the region. The effect of high primary
production on the CO2 system in the downstream plume is overshadowed by
the upwelling waters with high CO2.
AO-090
Molinari, J., S. Skubis, D. Vollaro, F. Alsheimer, and H.E. WILLOUGHBY.
Potential vorticity analysis of tropical cyclone intensification.
Journal of the Atmospheric Sciences, 55(6):2632-2644 (1998).
The interaction of marginal Tropical Storm Danny (1985) with an
upper-tropospheric positive potential vorticity anomaly was examined. The
intensification mechanism proposed earlier for mature Hurricane Elena
appears to be valid for Danny as well, despite significant differences in
the synoptic-scale environment and in the stage of the tropical cyclone
prior to the interaction. Both storms experienced rapid pressure falls as
a relatively small-scale positive upper potential vorticity anomaly began
to superpose with the low-level tropical cyclone center. The interaction
is described in terms of a complex interplay between vertical wind shear,
diabatic heating, and mutual advection among vortices at and below the
level of the outflow anticyclone. Despite this complexity, the
superposition principle appears to be conceptually useful to describe the
intensification of tropical cyclones during such interactions.
AO-091
MOLINARI, R.L., H.F. BEZDEK, M. Latif, and A. Groetzner. A comparison of
modeled and observed mean and decadal time-scale Atlantic air-sea
structure. Proceedings, Atlantic Climate Variability Meeting, Palisades,
New York, September 24-26, 1997. University Corporation for Atmospheric
Research, 78-79 (1998).
No abstract.
AO-092
MOLINARI, R.L., R.A. Fine, W.D. WILSON, J. Abell, M. McCartney, and R.
Curry. A fast-track for recently formed Labrador Sea Water: The Deep
Western Boundary Current of the North Atlantic. Proceedings, Atlantic
Climate Variability Meeting, Palisades, New York, September 24-26, 1997.
University Corporation for Atmospheric Research, 80 (1998).
No abstract.
AO-093
MOLINARI, R.L., R.A. Fine, W.D. WILSON, R.G. Curry, J. Abell, and M.S.
McCartney. The arrival of recently formed Labrador Sea Water in the Deep
Western Boundary Current at 26.5°N. Geophysical Research Letters,
25(13):2249-2252 (1998).
The Deep Western Boundary Current (DWBC) of the North Atlantic is a
principal conduit between the formation region for Labrador Sea Water
(LSW) and the oceanic interior to the south. Time series (1985-1997) of
hydrographic properties obtained in the DWBC at 26.5°N show that prior to
1994, temperature, salinity, and transient tracer properties within the
LSW density range showed little indication of recently formed parcels.
Properties characteristic of a newer version of LSW (cooler, fresher, and
higher tracer concentrations) were observed beginning in 1994 and
continuing through 1997. Longer time series of temperature and salinity,
developed from a regional data base, show both the1994 and a 1980-1981
event in the Abaco region. Both events are consistent with anomalies in
the Labrador Sea that occurred some 10 years earlier. The 10-year
transit time from the Labrador Sea to 26.5°N is less than the 18-year
transit time inferred from earlier studies.
AO-094
Montgomery, M.T., and J.L. FRANKLIN. An assessment of the balance
approximation in hurricanes. Journal of the Atmospheric Sciences,
55(12):2193-2200 (1998).
The validity of the traditional balance approximation for the asymmetric
flow above the boundary layer generally in hurricanes is examined here.
Scaling considerations of the divergence equation show that the validity
of the balance approximation hinges on the smallness of the
nondimensional product . The first term represents the ratio of
asymmetric horizontal divergence to asymmetric vertical vorticity for
azimuthal wavenumber, n, while the second term represents a Rossby number
based upon the azimuthal mean tangential wind and absolute vertical
vorticity of the hurricane vortex. Wind observations of Hurricane Gloria
(1985) indicate that this product is not at all small in the near-vortex
region (several hundred kilometers beyond the radius of maximum
tangential winds) where asymmetric convergence forced by surface friction
and cumulus convection is typically large. Although the Gloria
observations represent only a single case, there are dynamical reasons to
expect this product to be 0(1) just above the hurricane boundary layer in
steadily translating hurricanes. The meteorological relevance of these
results to the problem of balance dynamics in hurricanes is briefly
discussed.
AO-095
Nicholls, N., C.W. LANDSEA, and J. Gill. Recent trends in Australian
region tropical cyclone activity. Meteorology and Atmospheric Physics,
65:197-205 (1998).
The number of tropical cyclones observed in the Australian region (south
of equator; 105-160°E) has apparently declined since the start of
reliable (satellite) observations in the 1969/1970 season. However, the
number of more intense cyclones (with minimum pressures dropping to 970
hPa or lower) has increased slightly. The numbers of weak (minimum
pressures not dropping below 990 hPa) and moderate systems (minimum
pressures between 970 and 990 hPa) have declined. Possible reasons for
these different trends are discussed. The decline in the number of weaker
cyclones may at least partly reflect improved understanding of the nature
of some weak systems. The decline in the number of cyclones more intense
than 990 hPa primarily reflects the downward trend in the Southern
Oscillation Index (SOI). Previous work has demonstrated that the number
of tropical cyclones observed in the Australian region each cyclone
season is related to the value of the SOI prior to the start of the
cyclone season. This relationship is clearest with the number of moderate
cyclones. The SOI is only weakly related to the number of intense or weak
cyclones. The increase in the number of intense cyclones is not
attributable to the trend in the SOI. Nor is there clear reason, at
present, to suspect that it is artificial (i.e., due to changes in
observing or analysis techniques).
AO-096
Niyogi, D.S., J.J. CIONE, and S. Raman. Gulf Stream influence on the
North Carolina mesoclimate. Preprints, 2nd Conference on Coastal
Atmospheric and Oceanic Prediction, American Meteorological Society 78th
Meeting, Phoenix, AZ, January 12-16, 1998. American Meteorological
Society, Boston, 421-424 (1998).
No abstract.
AO-097
Ogden, J.C., S.L. Vargo, J.C. HENDEE, R. Timko, J.C. Humphrey, and T.C.
Moore. SEAKEYS 1998: An enhanced Florida Bay monitoring initiative.
Proceedings, 1998 Florida Bay Science Conference, Miami, Florida, May
12-14, 1998. Florida Sea Grant College Program, 118 (1998).
No abstract.
AO-098
ORTNER, P.B., M.J. Dagg, G.S. Kleppel, R. Brenner, and C. Tomas. Trophic
pathways in the pelagic environment of Florida Bay. Proceedings, 1998
Florida Bay Science Conference, Miami, Florida, May 12-14, 1998. Florida
Sea Grant College Program, 143-145 (1998).
No abstract.
AO-099
Özgökmen, T.M., and O.E. ESENKOV. Asymmetric fingers induced by the
nonlinear equation of state. Physics of Fluids, 10(8):1882-1890 (1998).
The impact of the nonlinearity in the equation of state associated with
the change in the thermal expansion coefficient with temperature on the
structure of fingers growing from an interface between two mixed layers
is investigated using a numerical model. It is shown that the
nonlinearity acts to enhance the buoyancy force acting on the descending
fingers with respect to that acting on the ascending fingers, resulting
in narrower and faster-growing descending fingers than ascending fingers.
The results are discussed with emphasis on the vertical variability of
properties along the fingers.
AO-100
Özgökmen, T.M., O.E. ESENKOV, and D.B. Olsen. A numerical study of layer
formation due to fingers in double-diffusive convection in a
vertically-bounded domain. Journal of Marine Research, 56(2):463-487 (1998).
The evolution of fingers in a double-diffusive system is investigated
using numerical integration of two-dimensional equations of motion for an
incompressible, Boussinesq fluid. The computational domain is periodic
in the horizontal direction and is closed with no-flux boundary
conditions in the vertical direction. The main result of this study is
the evolution of the system from initially linear profiles for both fast
and slow diffusing components to a layered state characterized by a
finger zone sandwiched between two mixed layers. The horizontal
boundaries in this system play an important role in the development of
the layered state. At the top and bottom boundaries, light and heavy
finger fluxes accumulate leading to the formation of mixed layers
exhibiting larger-scale eddies. In the quasi-equilibrium state, the
finger zone is characterized by broken wiggly fingers which do not extend
across the entire interface. The salinity flux at the mid-depth of the
domain is approximately proportional to the 4/3 power of the salinity
difference between the mixed layers, except for the initial phase and for
the run-down phase.
AO-101
PENG, T.-H., R. Key, and H.G. Ostlund. Temporal variations of bomb
radiocarbon in the Pacific Ocean. Marine Chemistry, 60(1-2):3-14 (1998).
The natural and anthropogenic components of the radiocarbon measurements
from seawater samples can be successfully separated by an improved
method, which is based on a very well-defined relationship between
natural radiocarbon and dissolved silica observed mainly during the
GEOSECS survey for waters beneath 1000 m depth. This relationship is
further reconfirmed by the 14C measurements from large volume samples
taken in the deep waters in the Pacific Ocean during the recent WOCE
survey program. Analysis of upper ocean 14C measurements made along
152°W, and north of 20°N, in the northeastern Pacific Ocean during NOAA's
CGC91 cruise, which is a part of the WOCE survey program, indicates that
the bomb 14C inventory in this part of the ocean has increased by 22%
since the GEOSECS measurements made in 1974. This increase is consistent
with the model prediction of 25% for the northern hemisphere ocean.
Change of the surface water bomb D14C values during this period is
insignificant. This feature is also consistent with the model
simulation. Results of this new analysis will provide useful information
of the temporal variations of bomb 14C inventory in the ocean, in
addition to the spatial distribution, which can be used as powerful
constraints in calibrating the global ocean carbon cycle models,
especially those based on three dimensional ocean general circulation
models, for estimating the uptake of CO2 by the ocean.
AO-102
Pielke, R.A., and C.W. LANDSEA. Normalized hurricane damages in the
United States: 1925-1995. Weather and Forecasting, 13(3):621-631 (1998).
Hurricanes are the costliest natural disasters in the United States.
Understanding how both hurricane frequencies and intensities vary from
year to year, as well as how this is manifested in changes in damages
that occur, is a topic of great interest to meteorologists, public and
private decision makers, and the general public alike. Previous research
into long-term trends in hurricane-caused damage along the U.S. coast has
suggested that damage has been quickly increasing within the last two
decades, even after considering inflation. However, to best capture the
year-to-year variability in tropical cyclone damage, consideration must
also be given toward two additional factors: coastal population changes
and changes in wealth. Both population and wealth have increased
dramatically over the last several decades and act to enhance the recent
hurricane damages preferentially over those occurring previously. More
appropriate trends in the United States hurricane damages can be
calculated when a normalization of the damages are done to take into
account inflation and changes in coastal population and wealth. With this
normalization, the trend of increasing damage amounts in recent decades
disappears. Instead, substantial multidecadal variations in normalized
damages are observed: the 1970s and 1980s actually incurred less damages
than in the preceding few decades. Only during the early 1990s does
damage approach the high level of impact seen back in the 1940s through
the 1960s, showing that what has been observed recently is not
unprecedented. Over the long term, the average annual impact of damages
in the continental United States is about $4.8 billion (1995 $),
substantially more than previous estimates. Of these damages, over 83%
are accounted for by the intense hurricanes (Saffir-Simpson categories 3,
4, and 5), yet these make up only 21% of the U.S.-landfalling tropical
cyclones.
AO-103
POWELL, M.D., and S.D. ABERSON. How well do we forecast the position and
time of hurricane landfall? Preprints, 16th Conference on Weather
Analysis and Forecasting, Symposium on the Research Foci of the U.S.
Weather Research Program, American Meteorological Society 78th Annual
Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological
Society, Boston, 9-12 (1998).
No abstract.
AO-104
POWELL, M.D., and S.H. HOUSTON. Surface wind fields of 1995 Hurricanes
Erin, Opal, Luis, Marilyn, and Roxanne at landfall. Monthly Weather
Review, 126(5):1259-1273 (1998).
Hurricanes Erin, Opal, Luis, Marilyn, and Roxanne were the most
destructive hurricanes of 1995. At landfall, Luis and Marilyn contained
maximum sustained winds (marine exposure) estimated at near 60 and 46 m
s-1, respectively. The strongest landfalling storm of the 1995 season,
Luis, decreased in intensity from a category 4 to 3 on the Saffir-Simpson
scale shortly before the eyewall crossed the Islands of Antigua, Barbuda,
St. Kitts-Nevis, St. Barthelemy, St. Martin, and Anguilla. Hurricane
Marilyn strengthened as it approached the U.S. Virgin Islands, with St.
Thomas bearing the brunt of the north and south eyewall winds of 46 m s-1
(marine exposure) and St. Croix being affected by the relatively weak
western eyewall peak winds of 35-40 m s-1 (marine exposure). For Luis and
Marilyn, only surface winds with marine exposures were analyzed because
of unknown small-scale interactions associated with complex island
terrain with 500-1000-m elevations. Wind engineering studies suggest that
wind acceleration over blunt ridges can increase or "speed up" winds by
20%-80%. Topographic effects were evident in damage debris analyses and
suggest that an operational method of assessing terrain-induced wind
gusts (such as a scaled down mesoscale model) is needed. After landfall
as a marginal hurricane over central Florida, Hurricane Erin regained
strength over the Gulf of Mexico with a well-defined radar reflectivity
structure. Erin struck the Florida panhandle near Navarre Beach with
maximum sustained surface winds of 35-40 m s-1 affecting the Destin-Ft.
Walton area. Hurricane Opal made landfall in nearly the identical area as
Erin, with maximum sustained surface winds of 40-45 m s-1, having
weakened from an intensity of nearly 60 m s-1 only 10 h earlier. Opal was
characterized by an asymmetric structure that was likely related to cold
front interaction and an associated midlevel southwesterly jet. Roxanne
struck Cozumel, Mexico, with sustained surface winds (marine exposure) of
46 s-1, crossed the Yucatan, and meandered in the southwest Gulf of
Mexico for several days. While in the Bay of Campeche, Roxanne's large
area of hurricane-force winds disabled a vessel, which led to the
drowning deaths of five oil industry workers. High-resolution wind
records are critical to preserving an accurate extreme wind climatology
required for assessment of realistic building code risks. Unfortunately,
power interruptions to Automated Surface Observing Stations (ASOS) on the
U.S. Virgin Islands (St. Croix, St. Thomas) and Destin, Florida,
prevented complete wind records of the eyewall passages of Marilyn and
Opal, respectively.
AO-105
POWELL, M.D., and S.K. Rinard. Marine forecasting at the 1996 centennial
olympic games. Weather and Forecasting, 13(3):764-782 (1998).
A team of meteorologists from the United States, Canada, and Australia
provided marine weather support to the sailing events of the 1996
Centennial Olympic Games, held in Wassaw Sound near Savannah, Georgia.
The team conducted research on the weather and climate and developed a
set of forecast products designed to inform athletes, volunteers, and
race managers of the wind, tidal current, wave, and weather behavior
expected each day during the pre-Olympic and Olympic periods. The Olympic
period proved to be a challenge with thunderstorms delaying, abandoning,
or postponing races on half of the days. Thunderstorm development and
movement was linked to the timing and strength of the sea breeze as well
as the direction and speed of the gradient wind. Numerous thunderstorm
warnings were issued with the assistance of the WSR-88D radar and the
Warning Decision Support System. Frequent lightning was a legitimate
safety concern due to the long distances between race courses and lack of
suitable shelter; fortunately no one was injured during the lightning
episodes. Forecasters benefited from access to a variety of monitoring
tools and models including real-time Olympic buoy wind and current time
series displays; satellite and radar imagery animation; 2-, 8-, and 10-km
resolution mesoscale models; a live video feed of race coverage; and
communications with forecasters aboard patrol craft offshore. Official
wind forecasts, mesoscale models, and a simple vector addition model
performed better than climatology and persistence as defined by mean
vector error and rms wind direction error. Climatology was difficult to
beat on the basis of wind speed error.
AO-106
PRONI, J.R., and J.C. Wilkerson. Underwater acoustic monitoring for
satellite rainfall estimation validation. Proceedings, 6th International
Conference for Precipitation, Mauna Lani Bay, Hawaii, June 29-July 1,
1998. NASA/NOAA, 2-10 (1998).
Application of underwater acoustic techniques to the monitoring of
rainfall over water is demonstrated at four acoustically distinct ocean
sites based on information in the 4-30 kHz frequency band. Rainfall
detection and classification as to type (convective or stratiform) are
possible because underwater sound spectral characteristics of rain are
different from the normally prevailing underwater background noise in the
ocean, and because there are distinct differences in the sound levels and
spectral shapes of the acoustic signature of the two rain types. Rain
type classification is determined by an acoustic discriminant, DR, which
is defined as the difference in the average spectral levels between the
10-30 and 4-10 kHz bands. Rainfall estimation potential is based on the
high correlation between sound spectral levels in decibels (in the 4-10
kHz frequency band) and radar reflectivity dBz. Data obtained from a
spatially distributed 12-hydrophone array on the ocean floor, at a depth
of 1.5 km, demonstrates the potential of monitoring rainfall at the sea
surface on spatial (420 km2) and temporal (five samples/minute) scales
suitable for validating precipitation estimates from remote sensors
carried on geostationary and polar orbiting satellites.
AO-107
PRONI, J.R., and J.C. Wilkerson. Wind-generated acoustic spectral
effects in the surf zone in the presence and absence of rainfall at Duck,
North Carolina. Proceedings, 16th International Congress on Acoustics
and 135th Meeting of the Acoustical Society of America, Seattle,
Washington, June 20-26, 1998. Journal of the Acoustical Society of
America, 103(5):2865-2866 (1998).
Concurrent underwater sound, wind, radar, and rainfall measurements were
made on November 5, 1992, off Duck, North Carolina. A wind speed
increment from 5 m/s to 13 m/s in 90 seconds resulted in a reduction in
the rainfall sound spectrum level beginning at about 50 kHz and extending
downward in frequency with time to about 10 kHz. The reduction in
rainfall-generated sound spectrum level with time is thought to be due to
sound absorption by the evolving wind-generated bubble field.
AO-108
PRONI, J.R., C. McArthur, and G. Schuster. Adaptive dredged material
discharge for the Port of Miami. Proceedings, Ports '98, Long Beach,
California, March 8-11, 1998. American Society of Civil Engineers,
1249-1257 (1998).
In a joint effort of the U.S. Army Corps of Engineers, the U.S.
Environmental Protection Agency, the National Oceanic and Atmospheric
Administration, the State of Florida, the Port of Miami, and the
University of Miami, a novel, environmentally adaptively controlled
procedure was developed wherein a vital port expansion and maintenance
dredging operation was carried out while affording maximum protection to
sensitive coral reefs. After establishing the existence and spatial
disposition of a residual water column discharge plume, via acoustic
backscattering methods, a real-time current measurement system was
established at the offshore dredged material disposal site to be
utilized. Dredged material discharges then proceeded on a schedule in
conformity with the ambient currents, so that material transport to the
coral reefs of concern was minimized.
AO-109
Quilfen, Y., B.Chapron, T. Elfouhaily, K.B. KATSAROS, and J. Tournadre.
Observations of tropical cyclones by high-resolution scatterometry.
Journal of Geophysical Research, 103(C4):7767-7786 (1998).
Unprecedented views of surface wind fields in tropical cyclones
(hereafter TCs) are provided by the European Remote Sensing Satellite
(ERS) C-band scatterometer. Scatterometer measurements at C band are
able to penetrate convective storms clouds, observing the surface wind
fields with good accuracy. However, the resolution of the measurements
(50 ´ 50 km2) limits the interpretation of the scatterometer signals in
such mesoscale events. The strong gradients of the surface wind existing
at scales of a few kilometers are smoothed in the measured features such
as the intensity and location of the wind maxima and the position of the
center. Beyond the ERS systems, the scatterometers on-board the ADEOS and
METOP satellites, designed by the Jet Propulsion Laboratory and by the
European Space Agency, respectively, will be able to produce measurements
of the backscattering coefficient at about 25 ´ 25 km2 resolution. A few
sets of ERS-1 orbits sampling TC events were produced with an
experimental 25 ´ 25 km2 resolution. Enhancing the resolution by a factor
of 2 allows location of the wind maxima and minima in a TC with a much
better accuracy than at 50 km resolution. In addition, a better
resolution reduces the geophysical noise (variability of wind speed
within the cell and effect of rain) that dominates the radiometric noise
and, hence, improves the definition of the backscattering measurements. A
comprehensive analysis of the backscattering measurements in the case of
high winds and high sea states obtained within TCs is proposed in order
to refine the interpretation of the wind vector derived from a
backscattering model that is currently only calibrated up to moderate
winds (<20 m/s) in neutral conditions. Observations of the TOPEX-POSEIDON
dual-frequency altimeter are also used for that purpose. Patterns of the
surface winds in TCs are described and characteristic features concerning
asymmetries in the maximum winds and in the divergence field are discussed.
AO-110
Rogers, S.M., and S.H. HOUSTON. Hurricane surge and wave conditions:
Research needs. Proceedings, Third International Symposium, Waves '97,
Virginia Beach, VA, November 3-7, 1997. American Society of Civil
Engineers, 1414-1424 (1998).
For many years, coastal engineers have recognized the importance of
reliable wave height and frequency information in the design of major
coastal structures. Over time, research by government agencies, such as
the U.S. Army Corps of Engineers and NOAA, and private interests such as
the offshore oil industry has made a substantial investment in wave
gages, wave hindcasting, and wave forecasting. Design needs for
breakwaters, jetties, coastal protection, offshore oil facilities, and
similar large-scale projects have driven the acquisition of better wave
data. Our ability to optimize design wave conditions has improved
significantly and with ongoing research is likely to continue to improve
in the future. Most designers and researchers would expect wave data is
most important for large coastal projects. However, in the United States
the most frequent application of design wave conditions is for the design
of single family homes and other coastal buildings. Each day hundreds of
coastal buildings in communities around the U.S. begin construction in
Coastal High Hazard Areas (or V-zones) as identified by the National
Flood Insurance Program (NFIP) and the Federal Emergency Management
Agency (FEMA). The NFIP prepares flood hazard maps specifying minimum
flood elevation standards that include wave height predictions during a
100-year storm surge, generally occurring during a hurricane or other
severe coastal storm. The NFIP uses several relatively simple models for
shoreline erosion, wave setup, wave runup and depth-limited linear waves.
Given the uncertainties inherent in any 100-year surge model, the simple
models are not unreasonable, including the use of depth limited, linear
waves. For many years we have been measuring water marks along the coast
following severe coastal storms with the goal of measuring the storm
surge, still water elevation, and/or wave height maximum. This paper will
report on case studies of U.S. hurricanes from U.S. hurricanes describing
the discrepancies between even the most reliable still water marks and
the lower limit of wave damage at the same locations. It is reassuring
that our ability to predict offshore wave conditions has improved.
However, it is clear that we have little understanding of the
water-levels and wave conditions during hurricanes where we need them the
most; that is, flooded building sites that are normally dry land. Some of
the discrepancies can be explained by measurement errors, wave setup,
wave runup, and localized setup in confined spaces and other factors, but
no rational theory can explain local variations. In short, we may have a
good wave gage record somewhere offshore and many post-storm water marks,
but we have little idea what water elevations and wave conditions
occurred in flooded building sites near the beach.Two problems result.
First, small buildings are usually designed to avoid waves by being
elevated on piling foundations. Without a reasonable understanding of
the wave conditions, buildings will be improperly elevated for
cost-effective designs (i.e., either too high or too low). A second
potentially more serious problem is that the high water marks will
eventually be used to calibrate the underlying storm surge models on
which all design conditions are based. Our lack of understanding
increases the risk of improperly calibrating the storm surge models,
which are also used to predict flood elevations much further inland than
those areas affected by waves. The authors believe that there is a
substantial need for wave and water-level measurements near coastal
building sites which are flooded during hurricanes and other design-level
storms. The frequent application of wave predictions is to design
cost-effective, storm-resistant buildings. The deployment of multiple,
self contained wave gages at preselected sites near coastal buildings
that are expected to be flooded during a landfalling hurricane is now a
practical research goal with recent improvements in instrumentation. It
is time to stop guessing the wave and water-level conditions and produce
some real measurements.
AO-111
ROUBICEK, A.J., S.L. GARZOLI, P.L. Richardson, C.M. Dumcombe Rae, and
D.M. Fratantoni. Benguela Current Experiment, R/V Seward Johnson Cruise
SJ9705, Cape Town, September 4, 1997-Recife, September 30, 1997. NOAA
Data Report, ERL AOML-33 (PB98-164775), 215 pp. (1998).
The main objective of this program is to study the pathways, velocity,
transport, and variability of the Benguela Current and its extension with
emphasis on tracking floats in the intermediate water. It is expected
that the results of this program will make a significant contribution
towards the understanding of inter-ocean (Indian to Atlantic) and
inter-basin (South and North Atlantic) exchange of intermediate water and
its role in heat and mass exchanges. This program is a component of KAPEX
(Cape of Good Hope Experiment), a joint U.S., German, and South African
experiment. In March 1997, a German cruise on the Polarstern led by W.
Zenk and O. Boebel launched 35 RAFOS floats and five sound sources
(including one of the U.S. sources near 20°S, 4°E) in the general area
west and southwest of Cape Town. During August 1997, a U.S. cruise on
the R/V Seward Johnson led by T. Rossby launched three sound sources east
and southeast of Cape Town; 50 RAFOS floats will be launched in the
Agulhas Current starting in November 1997. During the Benguela Current
Experiment cruise on the RV Seward Johnson in September 1997, 32 RAFOS
floats and two sound sources were launched in the general area west and
northwest of Cape Town. During KAPEX, over 100 RAFOS floats and nine
sound sources will measure ocean trajectories for the first time in the
Agulhas Current, in its rings which enter the South Atlantic, and in the
Benguela Current and its extension, which is the source of water moving
northward through the Atlantic in the meridional overturning circulation
cell. In addition, temperature, salinity, and velocity profiles will
document the water mass and velocity structure of the Benguela Current,
its extension, and several Agulhas rings.
AO-112
Shapiro, L.J., and S.B. GOLDENBERG. Atlantic sea surface temperatures and
tropical cyclone formation. Journal of Climate, 11(4):578-590 (1998).
It has long been accepted that interannual fluctuations in sea surface
temperature (SST) in the Atlantic are associated with fluctuations in
seasonal Atlantic basin tropical cyclone frequency. To isolate the
physical mechanism responsible for this relationship, a singular value
decomposition (SVD) is used to establish the dominant covarying modes of
tropospheric wind shear and SST, as well as horizontal SST gradients. The
dominant SVD mode of covarying vertical shear and SST gradients, which
comprises equatorially confined near-zonal vertical wind shear
fluctuations across the Atlantic basin, is highly correlated with both
equatorial eastern Pacific SST anomalies (associated with El Niño) and
west African Sahel rainfall. While this mode is strongly related to
tropical storms, hurricanes, and major hurricane frequency in the
Atlantic, it is not associated with any appreciable Atlantic SST signal.
By contrast, the second SVD mode of covarying vertical shear and
horizontal SST gradient variability, which is effectively uncorrelated
with the dominant mode, is associated with SST fluctuations concentrated
in the main tropical cyclone development region between 10°N and 20°N.
This mode is significantly correlated with tropical storm and hurricane
frequency but not with major hurricane frequency. Statistical tests
confirm the robustness of the mode, and lag correlations and physical
reasoning demonstrate that the SST anomalies are not due to the
developing tropical cyclones themselves. Anomalies of SST and vertical
shear during years where the mode has substantial amplitude confirm the
resemblance of the individual fields to the modal structure, as well as
the association of hurricane development with the warmer SSTs. Although
SSTs are of secondary importance to vertical shear in modulating
hurricane formation, explaining only ~10% of the interannual variability
in hurricane frequency over the ~50% explained by vertical shear, the
results support the conclusion that warmer SSTs directly enhance
development. The lack of correlation with major hurricanes implies that
the underlying SSTs are not a significant factor in the development of
these stronger systems.
AO-113
Shay, L., G.J. GOÑI, F.D. MARKS, J.J. CIONE, and P.G. BLACK. Role of
warm ocean features on intensity change: Hurricane Opal. Preprints,
Symposium on Tropical Intensity Change, American Meteorological Society
78th Annual Meeting, Phoenix, AZ, January 11-16, 1998. American
Meteorological Society, Boston, 131-138 (1998).
No abstract.
AO-114
Sheinbaum, J., J. Candela, J. Ochoa, A. Badan, I. Gonzalez, W.D. WILSON,
and R.H. SMITH. Velocity and transport measurements with a
lower-acoustic Doppler current profile in the Yucatan Channel: Some
preliminary results. Proceedings, Conference on the Transports and
Linkages of the Intra-Americas Sea (IAS), Cozumel, Mexico, November 1-5,
1997. IOC/IOCARIBE/MMS, 57 (1998).
We present preliminary results from the extensive surveys carried out
onboard UNAM'S R/V Justo Sierra using a shipboard ADCP and a CTD/LADCP
during December 1996 and May 1997 in the Yucatan Channel. These cruises
were part of the CANEK Project, a collaborative effort between CICESE,
ICMyL-UNAM, UAM (Mexico), NOAA (USA), and IOC (Cuba), to measure the
exchange between the Carribean Sea and the Gulf of Mexico. Velocity
measurements and transport estimates from both instruments are analyzed
and compared. The May 1997 cruise had a standard GPS instrument to fix
ship positions, which were recorded almost continuously (every second)
during the whole cruise. These data were filtered before velocity and
transport calculations were carried out. Details of the data processing
and sensitivity of absolute velocity estimates from the LADCP instrument
to the ship's position are discussed.
AO-115
Slansky, C.M., R.A. Feely, and R.H. WANNINKHOF. The stepwise linear
regression method for calculating anthropogenic CO2 invasion into the
North Pacific Ocean. In Biogeochemical Processes in the North Pacific,
S. Tsunogai (ed.). Japan Marine Science Foundation, Tokyo, 70-79 (1997).
No abstract.
AO-116
SWENSON, M.S., and H.F. BEZDEK. On ocean-atmosphere coupling in the North
Atlantic. EOS, Transactions, American Geophysical Union, 79(1):OS77 (1998).
We explore the geographical variability of the structure of the cross
correlation function between sea surface temperature anomalies (SSTA) and
anomalies of the sum of the latent and sensible heat fluxes (LSHFA) in
the North Atlantic based on summaries from the Comprehensive Ocean
Atmosphere Data Set (COADS) summaries from 1947-1990. Two distinct cross
correlation structures emerge, one of which dominates in the open ocean
at midlatitudes and the other of which dominates in the western boundary
current and in the tropics. The former is characterized by a strong
antisymmetry, while the latter is one-sided with a peak at zero-lag. A
simple stochastic model (vector first-order auto-regressive model) is
proposed to account for the observed structure. This is the simplest
auto-regressive model that can produce the antisymmetric aspect in the
cross correlation found in the open ocean midlatitude region. The model
reproduces the results with great fidelity, but requires essential mutual
coupling between SSTA and LSHFA to reproduce the open ocean midlatitudes
result. The residuals from the fit contain low-frequency behavior with
decadal time scales.
AO-117
Talley, L.D., and M.O. BARINGER. Preliminary results from WHP sections
18°N/15°E in the central Indian Ocean. Geophysical Research Letters,
24(22):2789-2792 (1997).
The R/V Knorr departed Colombo, Sri Lanka on March 10, 1995 and arrived
in Fremantle, Australia on April 15, 1995 to carry out its third WOCE
hydrographic leg in the Indian Ocean. Basic technical support was
provided by Scripps Institution of Oceanography's Oceanographic Data
Facility. Acoustic Doppler current profiler (ADCP) operations were
carried out by the University of Hawaii (Firing). The basic sampling
program was accomplished very smoothly. The full cruise report can be
obtained from the author. The cruise track is shown in the overview
figure for this newsletter, labeled I8N and I5E. The latter portion was a
nominal repeat of the 1987 section (Toole and Warren, 1993). The goals of
the sampling were to obtain a section through the center of the Central
Indian Basin, and to repeat the crossing of the northward flow of deep
water just to the west of Australia. Particular attention was paid to a
potential source of deep water for the Central Indian Basin, through a
sill in the NinetyEast Ridge, located at about 28°S. It was also possible
to deviate from the 32°S section, and sample in the deep water south of
Broken Ridge instead of along the top of the ridge. Between Broken Ridge
and Australia we chose to move the section slightly north of the original
position of I5E in order to resolve whether the deep flow splits around
Dirck Hartog Ridge. All stations were to within 10 m of the bottom and
included a 36-bottle rosette/CTD cast with lowered ADCP. A ship-mounted
ADCP was operated throughout. Basic station spacing was 30 nmi, and was
reduced at the equator, Sri Lankan, and Australian coasts and crossings
of the NinetyEast and Broken Ridges. The CTD data stream consisted of
elapsed time, pressure, two temperature channels, conductivity, oxygen,
altimeter, and transmissometer signals. Water samples were collected for
analyses of salt, oxygen, silica, phosphate, nitrate, and nitrite on all
stations and of CFC-11, CFC-12, carbon tetrachloride, helium-3, helium-4,
tritium, AMS C14, pCO2, total dissolved inorganic carbon, alkalinity, and
barium on selected stations. Water sample results were compared with
preliminary data acquired on prior WOCE legs and with earlier data. The
comparisons are available in the cruise report and show that the WOCE
data collected on legs 1 through 3 are a uniform data set; they also show
significant differences from Geosecs salinity and phosphate which are
attributable to measurement precision.
AO-118
Valdimarsson, H., S.-A. Malmberg, and M.H. BUSHNELL. SVP drifters in
Icelandic waters, 1995-1997: Preliminary results. Technical Session,
13th Data Buoy Cooperation Panel Meeting, La Reunion, October 1997. DBCP
Technical Publication 12, 91-101 (1998).
No abstract.
AO-119
WANG, C., and R.H. Weisberg. Observations of meridional scale frequency
dependence in the coupled tropical ocean-atmosphere system. Journal of
Geophysical Research, 103(C2):2811-2816 (1998).
It is generally observed in models of the coupled tropical
ocean-atmosphere system that the meridional scales for oscillations at
interannual periods are larger than an oceanic equatorial Rossby radius
of deformation. Using nine years of the high-resolution optimum
interpolation sea surface temperature (SST) product of the National
Oceanic and Atmospheric Administration (NOAA)/National Centers for
Environmental Prediction (NCEP), analyses are made on the frequency
dependence of the observed meridional scales, with emphasis on the
latitudinal structures in the central Pacific at 140°W. On the
relatively short intraseasonal and seasonal time scales, the SST
variations are found to occur over a meridional scale of the oceanic
equatorial Rossby radius of deformation suggested by conventional
equatorially trapped wave theory. In contrast to this, on the longer
annual and interannual time scales, the meridional scales are found to
increase beyond the oceanic equatorial Rossby radius of deformation. A
physical explanation for this meridional scale increase with decreasing
frequency in the coupled tropical ocean-atmosphere system is discussed.
AO-120
WANNINKHOF, R.H., and R.A. Feely. fCO2 dynamics in the Atlantic,
Pacific, and South Indian Oceans. Marine Chemistry, 60(1-2):15-31
(1998).
Subsurface fugacities of CO2 (fCO2(20)) can be used in combination with
total dissolved inorganic carbon (DIC) to precisely calculate total
alkalinity. Thus, it can be used to determine dissolution of calcium
carbonate (hard tissue) and remineralization of organic material (soft
tissue), to quantify saturation constants of calcite and aragonite in
seawater, and to characterize water masses. fCO2(20) is a good tracer of
biological transformation since it is thermodynamically related to the
other inorganic carbon system parameters and it has a dynamic range from
200 to 2000 matm in the world's ocean. Precision of fCO2 measurements is
better than 0.3% and the values are well calibrated using compressed gas
reference standards. Increases of fCO2(20) are observed as the water
masses age during movement from the Atlantic to the Indian and South
Pacific Oceans. As an example of the determination of the ratio of soft
tissue remineralization to hard tissue dissolution from fCO2(20) and DIC,
the trends along the 27.2 isopyncal for the subtropical gyres of the
three basins are investigated. Little CaCO3 dissolves along this
isopycnal in the Atlantic and the South Pacific while the soft tissue
remineralization to hard tissue dissolution ratio in the Indian Ocean is
4.5:1. The difference in this ratio along the 27.2 isopycnal appears to
be a combination of the calcite and aragonite saturation levels and the
supply of aragonite tests.
AO-121
Weisberg, R.H., and D.A. MAYER. Interhemisphere and intergyre exchange
processes. EOS, Transactions, American Geophysical Union, 79(45):F484
(1998).
Given that tropical ocean and atmosphere property fields have large
annual cycles, intergyre and interhemisphere exchanges are likely to be
seasonally dependent. Using COADS, we describe the annual variability of
the tropical Atlantic Ocean wind-driven circulation and its implications
for property exchanges. Focus is on three gyres: the anticyclonic
northern hemisphere subtropical gyre, the cyclonic tropical gyre north of
the equator, and the clockwise equatorial gyre. In the tropical gyre,
the Sverdrup circulation argues against a continuous western boundary
current for transporting water between the equatorial region and the
Caribbean in boreal winter. Instead, the Sverdrup circulation implies a
southeastward flowing boundary current, bringing to question the
mechanisms for the interhemisphere and intergyre exchanges of heat and
mass. A conceptual model is proposed involving two stages. First, the
western boundary current closing the clockwise equatorial gyre is
instrumental in transporting heat across the equator and storing warm
water mass between the North Equatorial Countercurrent ridge and the
North Equatorial Current trough in boreal summer. Transport farther
north into the subtropical gyre in boreal winter is then accomplished by
Ekman transport, as the seasonal change in wind stress deepens the
thermocline, allowing for northward Sverdrup transport over the region of
warmest waters. Once in the subtropical gyre, the Ekman transport
continues to be northward despite the Sverdrup transport reversing to be
southward. These stages constitute a rectification of the annual cycle
wherein different regions play additive roles during different times of
year. With Ekman and geostrophic transports being important, we also
look at how they combine to form divergence on the equator. We use
vertical velocity estimates from an equatorial central Pacific array of
moorings deployed during TIWE. Upwelling (downwelling) is observed above
(below) the EUC core, and while the divergence is centered on the
equator, poleward surface and equatorward subsurface flows are larger at
1°S than at 1°N. The results are consistent with interior fluid pathways
to the equator in the central Pacific. These gyre and vertical velocity
analyses demonstrate that three-dimensional and time dependent processes
are at work in transporting properties across hemispheres and gyres.
AO-122
Whung, P.-Y., and C.J. FISCHER. Input of atmospheric nitrogen species in
the Florida Bay area: Its role in the nitrogen budget of Florida Bay.
Proceedings, 1998 Florida Bay Science Conference, Miami, Florida, May
12-14, 1998. Florida Sea Grant College Program, 71 (1998).
No abstract.
AO-123
WILLOUGHBY, H.E. Tropical cyclone eye thermodynamics. Monthly Weather
Review, 126(12):3053-3067 (1998).
In intense tropical cyclones, sea level pressures at the center are
50-100 hPa lower than outside the vortex, but only 10-30 hPa of the total
pressure fall occurs inside the eye between the eyewall and the center.
Warming by dry subsidence accounts for this fraction of the total
hydrostatic pressure fall. Convection in the eyewall causes the warming
by doing work on the eye to force the thermally indirect subsidence.
Soundings inside hurricane eyes show warm and dry air aloft, separated by
an inversion from cloudy air below. Dewpoint depressions at the inversion
level, typically 850-500 hPa, are 10-30 K rather than the 100 K that
would occur if the air descended from tropopause level without dilution
by the surrounding cloud. The observed temperature and dewpoint
distribution above the inversion can, however, be derived by 100 hPa of
undilute dry subsidence from an initial sounding that is somewhat more
stable than a moist adiabat. It is hypothesized that the air above the
inversion has remained in the eye since it was enclosed when the eyewall
formed and that it has subsided at most a few kilometers. The cause of
the subsidence is the enclosed air's being drawn downward toward the
inversion level as the air below it flows outward into the eyewall.
Shrinkage of the eye's volume is more than adequate to supply the volume
lost as dry air is incorporated into the eyewall or converted to moist
air by turbulent mixing across the eye boundary. The moist air below the
inversion is in thermodynamic contact with the sea surface. Its moisture
derives from evaporation of seawater inside the eye, frictional inflow of
moist air under the eyewall, and from moist downdrafts induced as
condensate mixes into the eye. The moist air's residence time in the eye
is much shorter than that of the dry air above the inversion. The height
of the inversion is determined by the balance between evaporation,
inflow, and inward mixing on one hand and loss to the eyewall updrafts on
the other.
AO-124
WILSON, W.D. Constructing an IAS regional Global Ocean Observing
System. Proceedings, Conference on the Transports and Linkages of the
Intra-Americas Sea (IAS), Cozumel, Mexico, November 1-5, 1997.
IOC/IOCARIBE/ MMS, 66 (1998).
The Global Ocean Observing System (GOOS) was established as an
international program in 1993 by the IOC, WMO, UNEP, and ICSU. The main
elements are the collection and timely distribution of oceanic data and
products, including assessments, assimilation of data into numerical
prediction models, the development and transfer of technology, and
capacity building within participating member states to develop analysis
and application capability. To date, national GOOS operational
activities worldwide are primarily split between global programs
(supported almost entirely by a small number of highly developed
countries) and regional networks of linked coastal and nearshore
programs, such as EURO-GOOS in the EU and NEAR-GOOS in northeastern
Asia. The IOC suggests that "...In regions having existing IOC
Sub-Commissions (e.g., IOCARIBE), countries organizing regional GOOS
activities will do so in consultation with the Sub-Commission."
Subsequently, both IOC and IOCARIBE have expressed support for the
development of an IAS regional GOOS. Because of the nature of the
IOCARIBE member states, which contain far fewer autonomous national
oceanographic programs than eastern Asia or western Europe, the IAS GOOS
paradigm will have a somewhat different structure than NEAR-GOOS or
EURO-GOOS. It is hoped that this talk will promote a dialogue about
planning for the implementation of an IAS regional GOOS. For discussion
purposes, some important issues to be addressed in planning an IAS GOOS
include: (1) identification of customer concerns, e.g., fisheries,
climate studies, pollution management, etc., in keeping with the primary
GOOS goal of providing practical benefits to society; (2) Design of a
scientifically sound, expandable pilot observing system for continual
monitoring; (3) model development to provide a framework for data
synthesis and program expansion; (4) utilization of existing and planned
regional programs and regional parts of global programs as components for
cost-efficiency; and (5) regional dispersal of technology and capacity
building for synoptic data acquisition, management, and utilization.
AO-125
WILSON, W.D., and W.E. Johns. Velocity structure and transport in the
Windward Islands Passages. Deep Sea Research, 44(3):487-520 (1997).
During 1991-1994, repeated measurements of current structure and water
mass properties were made in the major southern passages to the Caribbean
Sea between Trinidad and Dominica. A total of 10 cruises were performed
in different seasons, consisting primarily of serial station occupations
in the Grenada, St. Vincent, St. Lucia, and Dominica Passages. This data
set is by far the most comprehensive available in these passages and
better determines the mean flow and range of variability than do previous
studies. The flow structure in these passages is characterized by a
strong and relatively stable inflow above the thermocline (approximately
the upper 100 m), and a more highly variable flow regime within and below
the thermocline. Typical near-surface inflow velocities in Grenada and
St. Vincent passages were 40-60 cm/s, with maximum observed currents of
90 cm/s. Frequently, counterflows were observed below this surface layer
flowing out of the Caribbean, trapped to the southern side of the
passages. This subsurface counterflow appeared to be strongest and most
prevalent in Grenada Passage, where outflow speeds as large as 30 cm s-1
were observed.
AO-126
WILSON, W.D., W. Johns, and E. JOHNS. Atlantic-Caribbean water exchange:
A quantitative summary of observations. Proceedings, Conference on the
Transports and Linkages of the Intra-Americas Sea (IAS), Cozumel, Mexico,
November 1-5, 1997. IOC/IOCARIBE/MMS, 65 (1998).
The need for good models of IAS circulation is growing as regional
researchers seek input for studies of air-ocean-land interaction, climate
variability, fisheries management, and pollution control. Proper
boundary conditions will be essential to the operation and validation of
these models. The water masses that enter, transit, and exit the IAS are
determined by interaction between the Atlantic thermohaline and
wind-driven circulations as well as regional modifications within the IAS
itself. Existing data on transports into, within, and out of the IAS are
quantitatively summarized to aid understanding of the IAS general
circulation, provide initial conditions, and serve as benchmarks for
model evaluation. Passages are categorized as inflows (passages of the
Antilles and Bahamas), internal (Pedro Banks, Yucatan Channel, western
Straits of Florida), or outflows (northern Straits of Florida). Inflow
passages are further subdivided by geographic location
(southern/northern); transport and water mass characteristics vary
markedly between northern and southern due to their location relative to
the western Atlantic gyre and wind field structure. Range of
variability, as well as mean flow values, are estimated when possible as
this is important to evaluation of model dynamics. A significant result
of this summary is a "best estimate" of mean transport distribution and
variability by region, passage, and depth levels. These values are
compared to transports derived from mean hydrographic and wind fields.
AO-127
WILSON, W.D., D. Wallace, R. Olivacce, R.A. Watlington, and W.E. Johns.
Monitoring the pulse of the DWBC in the Anegada Passage. Proceedings,
Conference on the Transports and Linkages of the Intra-Americas Sea
(IAS), Cozumel, Mexico, November 1-5, 1997. IOC/IOCARIBE/MMS, 63 (1998).
A serial station in the Anegada Passage, site of significant surface
transport and of the deepest exchange between the Atlantic Ocean and the
Caribbean Sea, is contributing to earlier observations at this location
to provide a useful background against which variability of the Deep
Western Boundary Current (DWBC) can be contrasted. Profiles of dissolved
inorganic carbon, dissolved oxygen, chlorofluorocarbons, and standard
hydrographic variables have successfully portrayed the several water
masses transiting this location at depths down to 1900 m. Significantly,
the southward advance of the prodigious flow Labrador Sea Water observed
at Abaco is expected to manifest itself at this station within the coming
year. ACTS is a project of the University of the Virgin Islands
conducted in partnership with Brookhaven National Laboratory and the NOAA
Atlantic Oceanographic and Meteorological Laboratory. The study, in
itself, represents a successful collaborative model whereby long-term
oceanic observations are conducted at minimal expense.
AO-128
YVON-LEWIS, S.A., and J. H. Butler. The uptake of atmospheric trace gases
by the ocean. EOS, Transactions, American Geophysical Union, 78(46):F93
(1997).
A global ocean-atmosphere model was developed to study the uptake of
CH3Br by the oceans. With this model we significantly reduced the
uncertainties in the partial atmospheric lifetime of CH3Br with respect
to its oceanic uptake (to, CH3Br) (Yvon and Butler, Geophys. Res. Lett.,
23(1), 53-56, 1996). Results from this model have also demonstrated that
the distribution of the oceanic degradation term is important in
caculating the partial atmospheric lifetime of a trace gas with respect
to oceanic loss processes and, consequently, its total atmospheric
lifetime (Yvon-Lewis and Butler, Geophys. Res. Lett., 24(10):1227-1230,
1997). It is now possible to determine the partial atmospheric lifetime
with respect to oceanic degradation of any trace gas for which the
oceanic degradation rate constant can be calculated. The results from
model runs for several trace gases including, CH3Br, CH3Cl, and CH3I,
suggested that the total atmospheric lifetimes of these trace gases
should be reduced by 38%, ~3%, and ~2%. These reductions are due solely
to the inclusion of the oceanic chemical degradation loss process. When
adapted for CH3CCl3, the model results reduced an earlier estimate for
the partial atmospheric lifetime of this trace gas with respect to
oceanic uptake by 31%. For some gases, these reductions are even greater
when biological removal is included. The results from the study of these
and other gases, including some HCFCs, will be presented.
AO-129
ZHANG, J-Z. Distinction and quantification of carry-over and sample
interaction in gas segmented continuous flow analysis. Journal of
Automatic Chemistry, 19(6):205-212 (1997).
The formulae for calculation of carry-over and sample interaction are
derived for the first time in this study. A scheme proposed by Thiers et
al. (two samples of low concentration followed by a high concentration
sample and low concentration sample) is verified and recommended for the
determination of the carry-over coefficient. The derivation demonstrates
that both widely used schemes of a high concentration sample followed by
two low concentration samples, and a low concentration sampled followed
by two high concentration samples, actually measure the sum of the
carry-over coefficient and sample interaction coefficient. A scheme of
three low concentration samples followed by a high concentration sample
is proposed and verified for determination of the sample interaction
coefficient. Experimental results indicate that carry-over is a strong
function of cycle time and a weak function of ratio of sample time to
wash time. Sample dispersion is found to be a function of sample time.
Fitted equations can be used to predict the carry-over, absorbance, and
dispersion given sample times, and wash times for an analytical system.
Results clearly show the important role of intersample air segmentation
in reducing carry-over, sample interaction, and dispersion.
AO-130
ZHANG, J.-Z., and G.A. BERBERIAN. Determination of dissolved silicate in
estuarine and coastal waters by gas segmented continuous flow
colorimetric analysis. In Methods for the Determination of Chemical
Substances in Marine and Estuarine Environmental Matrices, Supplement
1. Environmental Protection Agency, EPA 600/R-97-072, 366.0-1-366.0-2
(1997).
No abstract.
AO-131
ZHANG, J.-Z., and P.B. ORTNER. Effect of thawing conditions on the
recovery of reactive silicic acid from frozen natural water samples.
Water Research, 32(8):2553-2555 (1998).
A method for thawing frozen samples for silicic acid analysis is
recommended. The maximum recovery of silicic acid is achieved by thawing
the frozen samples in a refrigerator (at 4°C) in the dark for at least
four days. This method significantly improves the recovery of silicic
acid from frozen fresh water samples. It also permits close to 100%
recovery of reactive silicic acid from frozen seawater samples even after
three months storage.
AO-132
ZHANG, J.-Z., P.B. ORTNER, and C.J. FISCHER. Determination of nitrate
and nitrite in estuarine and coastal waters by gas segmented continuous
flow colorimetric analysis. In Methods for the Determination of Chemical
Substances in Marine and Estuarine Environmental Matrices, Supplement 1.
Environmental Protection Agency, EPA 600/R-97-072, 353.4.-1-353.4-2 (1997).
No abstract.
AO-133
ZHANG, J.-Z., P.B. ORTNER, C.J. FISCHER, and L.D. MOORE. Determination
of ammonia in estuarine and coastal waters by gas segmented continuous
flow colorimetric analysis. In Methods for the Determination of Chemical
Substances in Marine and Estuarine Environmental Matrices, Supplement
1. Environmental Protection Agency, EPA 600/R-97-072, 349.0-1-349.0-2
(1997).
No abstract.