OCED's Ocean Carbon Cycle Ronald H. Brown Master Readme File

Brown Underway Data

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Ronald H. Brown Master Readme File

INTRODUCTION:

The information presented in this file is applicable to all the data sets collected
on the NOAA ship Ronald H. Brown that are presented at:

www.aoml.noaa.gov/ocd/ocdweb/brown/brown_introduction.html.

Any temporary changes in this information will be noted in the readme files for
the individual expeditions.

Statement for use of data:

These data are made available to the public and the scientific community in the belief
that their wide dissemination will lead to greater understanding and new insights. The
availability of these data does not constitute publication of the data. We rely on the
ethics and integrity of the user to ensure that the AOML ocean carbon group receives
fair credit for its work. Please consult with us prior to use so we can ensure that the
quality and limitations of the data are accurately represented.

Platform Information:

In July of 1997, the Ocean Carbon Cycle Group (OCC) at NOAA's Atlantic Oceanographic and
Meteorological Laboratory (AOML) installed an automated instrument in the Brown's hydro
laboratory to measure the pCO₂ concentration in surface sea water. The Ronald H. Brown is
deployed for various multidisciplinary environmental research projects around the globe.
While the ship conducts the research that is the focus of a cruise, the pCO₂ instrument
makes regular measurements of the outside air and of the water flowing through the dedicated
scientific sea water system. The pCO₂ analytical system is regularly maintained by the survey
technician aboard the Brown. Occasionally, members of the OCC group will sail with the ship
for the targeted research and perform more extensive maintenance or upgrades. Three versions
of pCO₂ analytical system have been installed on the Brown.

Vessel Name: Ronald H. Brown

Class of Data: Surface ocean carbon dioxide concentrations

Scientists responsible for the technical quality of this pCO₂ dataset:

Rik Wanninkhof and Denis Pierrot
NOAA/AOML/Ocean Chemistry and Ecosystems Division
4301 Rickenbacker Causeway
Miami, FL 33149
Rik.Wanninkhof@noaa.gov
Denis.Pierrot@noaa.gov

Contact persons for this dataset:

Robert Castle and Kevin Sullivan
NOAA/AOML/Ocean Chemistry and Ecosystems Division
4301 Rickenbacker Causeway
Miami, FL 33149
Robert.Castle@noaa.gov
Kevin.Sullivan@noaa.gov

COMPONENT SPECIFICATIONS and ACCURACIES:

The accuracies of all components, when operating optimally, are such that the calculated
seawater fCO₂ has an accuracy of 2 uatm or better and the calculated mole fraction of
CO₂ (XCO₂) in air has an accuracy of 0.1 uatm.

Infrared Analyzer:
LI-COR model 6251 (2000 - February 2008)
Licor_6251_Manual.pdf
CO₂ resolution: 0.01 umol/m
CO₂ accuracy: ±1ppm at 350 ppm
Pressure resolution: 0.02 hPa
Internal pressure transducer accuracy: ±1.2 hPa (1.2 hPa = 1.2 mbar)
(manufacturer specifications: ±0.01% FS, where FS = 0-1150 hPa)

LI-COR model 6262 (1997 - 1999; March 2008 - present)
Licor_6262_Manual.pdf
CO₂ resolution: 0.01 umol/m
CO₂ accuracy: ±1ppm at 350 ppm
Pressure resolution: 0.02 hPa
Internal pressure transducer accuracy: ±1.2 hPa (1.2 hPa = 1.2 mbar)
(manufacturer specifications: ±0.01% FS, where FS = 0-1150 hPa)

Setra model 270 (June 2012 - present)
http://www.setra.com/ProductDetails/270_Baro.htm
Resolution: 0.015 hPa
Accuracy: ±0.15 hPa

For the LI-COR analyzers installed with the first instrumental systems, the internal
pressure transducers were used for processing the internal raw signal. After the third
instrumental system was installed, an external Setra 270 pressure transducer was connected
to the LI-COR 6262 for processing its internal raw signal.

Equilibrator Pressure:
Setra model 239, differential pressure (March 2008 - present)
http://www.setra.com/ProductDetails/model_239.htm
Resolution: 0.01 hPa
Accuracy: ±0.052 hPa
(manufacturer specifications: ±0.14% FS, where FS = ±7.5 inches WC)

The pressure of the laboratory space was measured with LI-COR analyzers under stopped
flow conditions, and this pressure was taken as the headspace pressure in the vented
equilibrator. With the third instrumental system, a differential pressure sensor
(Setra 239) was attached to the equilibrator. Both the LI-COR analyzer and the
differential pressure sensor were vented to the laboratory space. The absolute
pressure of the equilibrator headspace reported in data files for the third analytical
system is the sum of the Setra 239 differential pressure and the absolute pressure
measured at the analyzer exit under stopped flow condition.

Equilibrator Temperature:
Hart model 1560 (1997 - February 2008)
http://www.instrumart.com/assets/1560_manual.pdf
with Thermometrics AS125 thermister
http://www.ge-mcs.com/download/temperature/sases.pdf
Accuracy: ±0.0013°C
Resolution: 0.0001°C
The Hart 1560 was used to annually calibrate the 1000 ohm thermistor. Based on
reproducibility of the annual calibrations, the equilibrator water temperatures were
believed accurate to ± 0.02°C.

Hart model 1521 (March, 2008 - present)
http://www.instrumart.com/assets/1560_manual.pdf
Resolution: 0.001°C
Accuracy: ± 0.025°C

Sea Surface Temperature and Salinity:
YSI 600R Sonde (1997 - 2003)
http://science.nature.nps.gov/im/units/sean/AuxRep/FQ/FQ_YSI_6-series_sondes.pdf
Temperature resolution: 0.01°C
Temperature accuracy: ±0.15°C
Salinity resolution: 0.01‰
Salinity accuracy: ±1% of reading or 0.1‰ whichever is greater

SeaBird model SBE-45 (2004 - present)
http://www.seabird.com/pdf_documents/manuals/45_017.pdf
Temperature resolution: 0.0001°C
Temperature accuracy: ±0.002°C
Salinity resolution: 0.0002‰
Salinity accuracy: ±0.005‰

SeaBird model SBE-21 (1997 - present; maintained by ship)
http://www.seabird.com/pdf_documents/manuals/21_026.pdf
Temperature resolution: 0.001°C
Temperature accuracy: ±0.01°C
Salinity resolution: 0.002‰
Salinity accuracy: ±0.05‰

Atmospheric Pressure (maintained by ship):
Vaisala model PTB330 barometer (10 meters above sea level; maintained by ship)
http://www.vaisala.com/Vaisala%20Documents/User%20Guides%20and%20Quick%20Ref%20Guides/
PTB330_User_Guide_in_English.pdf
Resolution: 0.01 hPa
Accuracy: ±0.10 hPa

INSTRUMENT DESCRIPTION and CONFIGURATION:

The general principle of instrumental design can be found in Wanninkhof and Thoning
(1993), Ho et al. (1995), and Feely et al. (1998) and Pierrot et al. (2009). The
concentration of CO₂ in the headspace gas was measured using the adsorption of
infrared (IR) radiation by the CO₂ molecule. The LI-COR® analyzer passed IR
radiation through two cells. The reference cell was constantly flushed with a gas
of known concentration. For the first two instrumental systems (1997 - February, 2008),
the reference gas contained CO₂ with concentration close to outside air. For the
third instrumental system from General Oceanics (March, 2008 - present), the
reference gas was CO₂-free air. The sample cell was flushed with the gas of interest
(standard, outside atmosphere, or headspace gas from equilibration chamber). A
vacuum-sealed, heated filament was the broadband IR source. The IR radiation
alternated between the two cells via a chopping shutter disc spinning at 500 Hertz.
An optical filter selected an adsorption band specific for CO₂ (4.26 micron)
to reach the detector. The solid state (lead selenide) detector was kept at
-5 degrees C for excellent stability and low signal noise (less than 0.2 ppm).

The effects of water vapor on the analyses were kept to a minimum by removing as
much water as possible before the sample gas reached the IR analyzer. Water vapor
was first condensed out of the sample gas stream by cooling to approximately 6
degrees C. The first two instrumental systems used glass condensers and a circulating
water bath. The third instrumental system used a thermoelectric device and milled
aluminum block. Water vapor was further removed by pushing the sample gases through
a canister of magnesium perchlorate in the first two systems or through Nafion� gas
dryers in the third system. The counterflow gas in the dryers was pre-dried outside
air at reduced pressure. Typical water content of the analyzed gases was less than
3 millimoles/mole with approximately 90% of the water being removed.

The infrared analyzers were calibrated regularly using three or four standard gases
(200 - 550 ppm) from the ESRL laboratory in Boulder, CO, which are directly traceable
to the WMO scale. Any value outside the range of the standards should be considered
approximate (+/-5 ppm). While individual data points above the highest standard or
below the lowest standard may be less accurate, the general trends would be indicative
of the seawater chemistry. The exact concentrations of the standards used on a particular
cruise are listed in most of the individual readme files. The flushing rate during
standard (STD) analyses was 50 - 80 ml/min.

All three instrumental systems measured CO₂ in atmospheric air. Outside air was
constantly being pulled (6 liters/min maximum) from an inlet on the bow mast
through approximately 75 meters of tubing (1 cm OD Dekoron) to the analytical
system. The flushing rate of the LI-COR analyzer during outside air (ATM) analyses
was 60 - 150 ml/min.

A dedicated scientific seawater inlet at an approximate depth of 5 meters is the
source of water flowing throughout the ship. For the first (1997 - 1999) and
second (2000 - February, 2008) instrumental systems, seawater was pushed through a
large showerhead equilibrator (8 L of water under 16 L of headspace) at 10 L/min.
For the third instrumental system (March, 2008 - present), seawater was pushed
through a smaller spray head equilibrator (0.5 L of water under 0.7 L of headspace)
at 2 L/min. The initial equilibrator in the third system (March, 2008 -
February, 2010) was fabricated using a filter housing (ColeParmer, U-010509-00).
In March, 2010, an equilibrator with a water jacket for better thermal stability
was installed and was only slightly larger (0.6 L of water under 0.8 L of headspace).
During EQU analyses the headspace gas was pulled from the equilibrator chamber,
pushed through the analyzer, and returned to the equilibrator at 60 - 150 ml/min.

In the first two analytical systems, the water temperature in the equilibrator
as measured with a 20-cm long, 1000 Ohm thermistor that was fully submerged via
a port in the bottom of the chamber. The thermistor was calibrated annually
against a Hart Scientific 1560 Black Stack module with platinum resistance NIST
traceable thermistor. Based on reproducibility of the annual calibrations, the
temperatures were believed accurate to ± 0.02 °C. In the third analytical system,
the water temperature was measured with a Hart 1521 thermometer whose probe was
submerged about 5 cm.

The headspace of the equilibrator for the first two instrumental systems was vented to
the surrounding laboratory space through an internal baffle and then through an external
open enclosure that was constantly flushed with outside air. For the third instrumental
system, the main equilibrator was vented through a smaller secondary equilibrator.
Any laboratory gas drawn into the equilibrators was 'pre-equilibrated' with flowing sea
water in the secondary equilibrator before reaching the main equilibrator.

In addition to the pCO₂ analytical system, the OCC group maintained a thermosalinograph
(TSG) in the hydro laboratory. The first TSG was a YSI 600R sonde that also contained
a dissolved oxygen sensor. In 2004, a Sea-Bird (SBE) model 45 TSG replaced the YSI TSG
at the manifold distributing seawater in the hydro laboratory. In March, 2008, the SBE45
was relocated to immediately next to the pCO₂ analytical system. After a cruise, the
salinity measured by the OCC TSG was compared with the values from the ship?s SBE21, and
the salinity measurements of higher quality were used in the calculations of fCO₂.
An Aanderaa oxygen sensor was added to the pCO₂ instrumental system in April 2013.

These additional sensors along with various sensors maintained by the ship (e.g. GPS,
SST, fluorometer, wind speed and direction) were logged in real time with the CO₂
measurements. These data were used in processing the CO₂ data, especially during the
quality assurance procedures. Not all of the logged data is presented in the posted
data files. Requests for the ancillary data may be submitted to Mr. Bob Castle,
whose contact information is listed above.

The first two instrumental systems ran an hourly cycle comprised of the three STD
gases, four EQU analyses, three ATM analyses, and then four EQU analyses. The
infrared analyzer was flushed with the chosen gas at least four minutes before the
flow was stopped. After waiting 10 seconds for the analyzer to reach ambient pressure,
most of the raw data was recorded. This data included the infrared analyzer, the
numerous sensors internal to the CO₂ instrumental systems, and the ship?s sensors
chosen for inclusion in the data feed to the instrumental system. The timing
of the hourly cycle was based on the computer time internal to the instrumental
system. The processed data is associated and posted with the UTC time logged
from the ship's GPS.

The third instrumental system ran a sequence comprised of the four STD gases,
five ATM analyses, and then at least fifty EQU analyses. When data acquisition was
initiated, the zero and span of the analyzer were set with CO₂-free air and the
highest standard gas, respectively. At least six complete sequences (4 STD,
5 ATM, 50-65 EQU) were done before the zero and span of the analyzer was set again.
For the first analysis of any type, the analyzer was flushed for four minutes
before the 10 seconds of stopped flow and data recording. For repeated analyses
of sample gas (i.e. ATM or EQU), the analyzer was flushed 2 - 2.5 minutes. The
analytical sequence was configured to calibrate the analyzer every 2.5 - 3.3
hours and to set the zero and span at least once a day.

CALCULATIONS:

For data collected with the first two instrumental systems (1997 - February, 2008),
the xCO₂ values of ambient air and equilibrated headspace gas are calculated by
fitting a second-order polynomial through the hourly averaged response of the
detector versus xCO₂ values of the standards. For data collected with the third
instrumental system (March, 2008 - present), the measured xCO₂ values are linearly
corrected for instrument response using the standard measurements (see Pierrot et al.,
2009).

For ambient air and equilibrator headspace the fCO₂a or fCO₂eq is calculated assuming
100% water vapor content:

fCO₂ = xCO₂ P (1-pH2O) exp[(B11+2d12)P/RT]

where fCO₂ is the fugacity in ambient air or equilibrator headspace, pH2O is the water
vapor pressure at the sea surface or equilibrator temperature, P is the equilibrator or
outside atmospheric pressure (in atm), T is the SST or equilibrator temperature (in K)
and R is the ideal gas constant (82.057 cm^3·atm·deg^-1·mol^-1). The exponential term
is the fugacity correction where B11 is the first virial coefficient of pure CO₂

B11 = -1636.75 + 12.0408 T - 0.0327957 T^2 + 3.16528E-5 T^3

and

d12 = 57.7 - 0.118 T

is the correction for an air-CO₂ mixture in units of cm^3·mol^-1 (Weiss, 1974).

The calculation for the fugacity at SST involves a temperature correction term for the
changes in fCO₂ due to changes in water temperature while the water passes through the
pump and connecting pipe within the ship. The water in the equilibrator was typically
0.2 °C warmer than SST. For all data before 2006, the empirical temperature correction
from equilibrator temperature to SST is outlined in Weiss et al. (1982):

dln(fCO₂) = (Teq-SST)(0.0317 - 2.7851E-4 Teq - 1.839E-3 ln(fCO₂eq))

where dln(fCO₂) is the difference between the natural logarithm of the fugacity at Teq
and at SST. Teq and SST are the equilibrator and sea surface temperatures in degrees C,
respectively.

Starting in 2006, the fugacity as measured in the equilibrator is corrected for the
temperature difference between equilibrator chamber and SST using the empirical correction
outlined in Takahashi et al. (1993).

fCO₂(SST) = fCO₂(teq)exp[0.0423(SST-teq)]

where fCO₂(SST) is the fugacity at the sea surface temperature and fCO₂(eq) is the fugacity
at the equilibrator temperature.

The amount of time between the sea water passing by the SST sensor and the water flowing
through the equilibrator is estimated before assigning an SST value to each analysis.
The patterns in the temperature records for the equilibrator and for SST over time are
compared, and a time offset that optimizes the match of these patterns is determined.
The time offset is applied to the SST measurements. A linear interpolation between the
time-adjusted SST data yields the SST value assigned to each CO₂ analysis and used in the
fugacity calculations.

DATA FILE STRUCTURE (1997-2003):

COLUMN HEADER EXPLANATION

1. JD Julian Day

2. Date Date (month,day,year)

3. Time Greenwich Mean Time

4. Lat Latitude in decimal degrees (negative
values are in southern hemisphere)

5. Long Longitude in decimal degrees (negative
values are in western latitudes)

6. xCO₂,w Mixing ratio of CO₂ (dry) in headspace
of equilibrator (in parts per million)

7. xCO₂,a Mixing ratio of CO₂ (dry) from the bow
of ship (15 m above water)

8. EqTemp Temperature in equilibrator (in degrees C)

9. Pressure Pressure in laboratory (in millibar)

10. SST(TSG) Sea surface temperature measured at the
water intake 5 m below the water line
(in degrees centigrade)

11. SAL(TSG) Salinity measured at the water intake
5 m below the water line

12. fCO₂w,eq Fugacity of water in equilibrator
calculated according to DOE (1994)
in microatmospheres

13. fCO₂w,in situ Fugacity of water at SST calculated
from algorithm of Weiss et al.
(1982)

14. fCO₂a Fugacity of CO₂ in air

15. dfCO₂ Water-air fugacity difference

DATA FILE STRUCTURE (2004 - February 2008):

Starting in 2004, the appearance of the web page and the data file structure
were changed. The current charts for the individual cruises contain color-coded
cruise tracks representing the fCO₂ in surface water. The new data files include
auxiliary meteorological, oceanographic, and ship's navigation data; plus the 'Date'
field has a new format. These changes follow the recommendations of the International
Ocean Carbon Coordination Project (http://ioc.unesco.org/ioccp). The purpose of this
project is to standardize measurement techniques and QA/QC procedures, coordinate
international ocean carbon observations, and improve accessibility to carbon data
sets in order to better meet the needs of the research community. Most of the
additional data is taken from the ship's computer system "as is" with no quality
control. Quality controlled meteorological data for the Ron Brown can be obtained from
the Center for Ocean-Atmosphere Prediction Studies:
http://coaps.fsu.edu/RVSMDC/cgi-bin/nonwoce-ship.cgi?id=WTEC.

The following list gives the new data fields with units and notes about the changes in
format.

COLUMN HEADER EXPLANATION

1. GROUP/SHIP AOML_Brown for all Ron Brown data (NEW)

2. CRUISE_DESIGNATION RBYYYYNN. All Ron Brown data will give
the cruise designation RB followed by
4-digit year and the 2-digit cruise
number (NEW)

3. JD_GMT Decimal year day (same as in old files)

4. DATE_DDMMYYYY The date format has been changed to comply
with the IOCCP recommendations (CHANGED)

5. TIME_HH:MM:SS GMT Time (same as old files)

6. LAT_DEC_DEGREE Latitude in decimal degrees (negative
values are in southern hemisphere)

7. LONG_DEC_DEGREE Longitude in decimal degrees (negative
values are in western latitudes)

8. xCO₂W_PPM Mole fraction of CO₂ in the equilibrator
at equilibrator temperature (Teq)
in parts per million

9. xCO₂A_PPM Mole fraction of CO₂ in air in parts per
million

10. PRES_EQUIL_hPa Barometric pressure in the lab in
hectopascals (1 hectopascal = 1 millibar)

11. PRES_SEALEVEL_hPa Barometric pressure, ship's sensor,
corrected to sea level in hectopascals
(NEW)

12. EqTEMP_C Temperature in equilibrator water in
degrees centigrade

13. SST(TSG)_C Temperature from the ship's thermosalinograph
in degrees centigrade

14. SAL(TSG)_PERMIL Salinity from the ship's thermosalinograph
in Practical Salinity Scale

15. WATER_FLOW_L/MIN Water flow through equilbrator in liters
per minute (NEW)

16. GAS_FLOW_IR_ML/MIN Gas flow through the Licor infrared analyzer
before the flow is stopped in milliliters per
minute (NEW)

17. TEMP_IR_C Temperature of the Licor infrared analyzer
sample cell in degrees centigrade (NEW)

18. PRES_IR_hPa Pressure in the Licor infrared analyzer in
hectopascals (NEW)

19. SHIP_HEADING_TRUE_DEGREE Ship's heading in degrees with 0 = North
and 90 = East (NEW)

20. SHIP_SPEED_KNOT Ship's speed in knots (NEW)

21. WIND_DIR_REL_DEGREE Wind direction relative to the ship in degrees
with 0 = from the bow and 90 = from starboard
(NEW)

22. WIND_SPEED_REL_M/S Wind speed relative to the ship in meters per
second (NEW)

23. fCO₂W@SST_uATM Fugacity of CO₂ in sea water in microatmopheres

24. QC_FLAG_WATER Quality control flag for sea water xCO₂ and
fCO₂ values with 2 = good, 3 = questionable,
4 = bad and 9 = no measurement (NEW)

25. fCO₂A_uATM Fugacity of CO₂ in air in microatmospheres

26. QC_FLAG_WATER Quality control flag for air xCO₂ and
fCO₂ values with 2 = good, 3 = questionable,
4 = bad and 9 = no measurement (NEW)

27. dfCO₂_uATM Sea water fCO₂ - air fCO₂ in microatmospheres,
the average air value for the current hour

28. FLUORO_uG/L Reading from Turner 10-AU fluorometer in
micrograms per liter (NEW)

29. WIND_SPEED_TRUE_M/S True wind speed in meters per second (NEW)

30. WIND_DIR_TRUE_DEGREE True wind direction in degrees, 0 = North
and 90 = East (NEW)

31. AIR_TEMP_C Outside air temperature in degrees centigrade
(NEW)

DATA FILE STRUCTURE (2008 - 2009):

When the third instrumental system was installed, the format of the final data file was also
changed. The most significant changes were related to ATM analyses. All acceptable ATM
analyses are included in the final data file and columns for interpolated ATM xCO₂ and
fCO₂ were added.

Extra explanations of the quality of questionable analyses (QC flag =3) are placed in the new
QC_SUBFLAG column. The QC flags apply to the fCO₂ results for EQU analyses and to the xCO₂
result for ATM analyses and are provided as an aid to the interpretation of the CO₂ data.
Stringent minimum and maximum values for numerous parameters (e.g. temperature difference
between the equilibrator temperature and SST) have been established by CO₂ researchers
(see Pierrot et al., 2009). These ranges were chosen so that if each parameter were within
heir stringent range, the resulting CO₂ data would almost certainly be good. If a parameter
is outside its range or if a parameter is estimated from surrounding good values, the quality
flag of that data record is set to 3 and a text explanation could be added in the QC_SUBFLAG
column. The resulting CO₂ data could be good; however, investigators should determine whether
these data are valid for their purposes.

COLUMN HEADER EXPLANATION

1. Group_Ship AOML_BROWN for all Ron Brown data

2. Cruise ID RBYYNN where YY is the 2-digit year
and NN is the cruise number for that
year

3. JD_GMT Decimal year day

4. DATE_UTC_mmddyyyy UTC Date

5. TIME_UTC_hh:mm:ss UTC Time (24 hour clock)

6. LAT_dec_degree Latitude in decimal degrees (negative
values are in southern hemisphere)

7. LONG_dec_degree Longitude in decimal degrees (negative
values are in western latitudes)

8. xCO₂_EQU_ppm Mole fraction of CO₂ in the equilibrator
at EQU temperature in parts per million

9. xCO₂_ATM_ppm Mole fraction of CO₂ in air in parts per
million

10. xCO₂_ATM_interpolated_ppm Bracketing average air values interpolated
to time of EQU analysis

11. PRES_EQU_hPa Barometric pressure in the equilibrator in
hectopascals

12. PRES_ATM@SSP_hPa Outside barometric pressure, corrected to
sealevel in hectopascals

13. TEMP_EQU_C Equilibrator water temperature in degrees
centigrade

14. SST_C Sea surface temperature in degrees centigrade

15. SAL_permil Salinity from the ship's TSG or TSG in the
Hydro Lab in Practical Salinity Units

16. fCO₂_SW@SST_uatm Fugacity of CO₂ in sea water in microatmopheres

17. fCO₂_ATM_interpolated_uatm Fugacity of CO₂ based on the interpolated xCO₂,
in microatmospheres

18. dfCO₂_uATM fCO₂_SW@SST_uatm minus fCO₂_ATM_interpolated_uatm

19. WOCE_QC_FLAG Quality control flag for Equ fCO₂ values and
Atm xCO₂ with values with 2 = good, 3 = questionable,
4 = bad

20. QC_SUBFLAG Subflag text string for values flagged as 3

21. WATER_FLOW_L/MIN Water flow through the equilbrator in liters
per minute

22. GAS_FLOW_IR_ML/MIN Gas flow through the Licor sample cell
in milliliters per minute

23. SHIP_SPEED_KNOT Ship's speed in knots

24. SHIP_HEADING_TRUE_DEGREE Ship's heading in degrees with 0 = North
and 90 = East

25. AIR_TEMP_C Outside air temperature in degrees centigrade

26. WIND_DIR_TRUE_DEGREE Absolute (true) wind direction in degrees

27. WIND_SPEED_TRUE_M/S Absolute (true) wind speed in meters per second

28. WIND_SPEED_REL_M/S Wind speed in meters per second relative to
the ship

29. WIND_DIR_REL_DEGREE Wind direction in degrees relative to the ship

30. FLUORO_uG/L Reading from Turner 10-AU fluorometer in
micrograms per liter

DATA FILE STRUCTURE (2010 - present):

Starting with cruise RB1001, several columns of data not directly used in computations of
fCO₂ or xCO₂ were removed from the final data file format. Starting in 2013, a column for
ExpoCode was added.

COLUMN HEADER EXPLANATION

1. Expocode Expedition code, where '33RO' is the NODC
identifer YYYYMMDD is the UTC date that the
ship starts the expedition

2. Group_Ship AOML_RonaldH.Brown for all Ronald H. Brown data,
(if present)

3. Cruise ID RBYYNN where YY is the 2-digit year
and NN is the cruise number for that
year, (if present)

4. JD_GMT Decimal year day

5. DATE_UTC_ddmmyyyy UTC Date

6. TIME_UTC_hh:mm:ss UTC Time (24 hour clock)

7. LAT_dec_degree Latitude in decimal degrees (negative
values are in southern hemisphere)

8. LONG_dec_degree Longitude in decimal degrees (negative
values are in western latitudes)

9. xCO₂_EQU_ppm Mole fraction of CO₂ in the equilibrator
at EQU temperature in parts per million

10. xCO₂_ATM_ppm Mole fraction of CO₂ in air in parts per
million

11. xCO₂_ATM_interpolated_ppm Bracketing average air values interpolated
to time of EQU analysis

12. PRES_EQU_hPa Barometric pressure in the equilibrator in
hectopascals

13. PRES_ATM@SSP_hPa Barometric pressure, ship's barometer,
corrected to sealevel in hectopascals

14. TEMP_EQU_C Equilibrator water temperature in degrees
centigrade

15. SST_C Sea surface temperature in degrees centigrade

16. SAL_permil Salinity from the Micro TSG in the Hydro
Lab in Practical Salinity Units

17. fCO₂_SW@SST_uatm Fugacity of CO₂ in sea water in microatmopheres

18. fCO₂_ATM_interpolated_uatm Fugacity of CO₂ based on the interpolated xCO₂,
in microatmospheres

19. dfCO₂_uATM fCO₂_SW@SST_uatm minus fCO₂_ATM_interpolated_uatm

20. WOCE_QC_FLAG Quality control flag for Equ fCO₂ values and
Atm xCO₂ with values with 2 = good, 3 = questionable,
4 = bad

21. QC_SUBFLAG Subflag text string for values flagged as 3

REFERENCES:

DOE (1994). Handbook of methods for the analysis of the various parameters of the carbon
dioxide system in sea water; version 2. DOE.
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AOML's Ocean Chemistry and Ecosystems Division

Ronald H. Brown Master Readme File