Printer Friendly Version
Back to Intensity Change projects | Back to Main Projects Page


Collaborators : Peter Black (HRD) Flight Planning, Dropsondes
Robert Black (HRD) Cloud Physics
Eric Uhlhorn (HRD) Hurricane surface flux
Gustavo Goni (AOML/HRD) Ocean heat content
Paul Chang (NESDIS/ORA) Satellite applications
David McLaughlin (UMass) SFR, web, data archive
Jeff French (ARL) ET Probe, BAT
Eric D’Asaro (APL/UW) Lagrangian Float
Kerry Emanuel (MIT) Theory, dropsondes
Eric Terrill (Scripps) Floats
Jeff Nystuen (APL/UW) Acoustics of wave and precipitation
Ken Melville (Scripps) Wave breaking
Ed Walsh (NASA) SRA
Chris Fairall (ETL) Sea Spray (CPC)
Bill Asher (APL/UW) Sea Spray (PDA)
Pearn Niiler (Scripps) Drifters
Wil Drennan (UM/RSMAS) Moisture flux
Shuyi Chen (UM/RSMAS) Coupled modeling
Nick Shay (UM/RSMAS) Ocean responce
Chi-Sann Liou (NRL) COAMPS modeling


Our primary goal is to improve our understanding of air-sea surface flux processes in high winds, specifically in the complex conditions of tropical hurricanes where swell, sea spray and secondary boundary layer circulations play a role. Our ultimate goal and prime motivation for this work is to parameterize these new observations and improve the accuracy of hurricane intensity prediction.


The objective of this work is to develop a new surface wave-dependent flux parameterization for the high wind hurricane boundary layer containing secondary (roll-vortex) circulations over fetch limited seas in the presence of sea spray and one or more swell components from an airborne platform. We propose to test the following hypotheses:

  1. that surface momentum exchange coefficients increase with wind speed for moderate winds (>30 m/s), are enhanced by fetch-limited waves or opposing swell, but level off or decrease above a high wind threshold (>45 m/s), especially in quadrants where swell has a significant downwind component,
  2. that compensating mechanisms for enhanced surface air-sea enthalpy fluxes over and above current parameterizations must exist for storm maintenance and growth above some high-wind threshold wind speed, and
  3. that candidate mechanisms are separable and can be estimated, such as a) enhanced turbulent fluxes due to wave interactions, b) spray evaporation and c) secondary flow circulations (roll-vortex type).


Our approach is to implement a multifaceted observational program among several investigators to simultaneously measure air-sea fluxes using several independent methods while at the same time measuring two-dimensional surface wave spectra, as well as spray droplet spectra , in wind speed regimes ranging from 20-40 m/s, and possibly higher. The secondary goal is to use existing data sets to inter-compare various published wave-dependent bulk flux parameterizations, with and without wave age effects and with and without spray parameterizations, using never-before-available surface inputs from GPS dropsondes, AXBTs, model-generated as well as remotely-measured wave spectra and remotely-measured surface winds in gale- and hurricane-force conditions.

Our strategy will be to obtain new parameterizations of momentum, heat and moisture fluxes from these observations including accurate estimates of the exchange coefficients as a function of wind speed and to estimate the modulation of the fluxes by fetch-limited wind waves, long-wavelength swell, sea spray and PBL secondary circulations, i.e.‘roll vortices’.

CBLAST experiments flown

Back to Intensity Change projects | Back to Main Projects Page

Last modified: 5/16/2003

Stay Connected