26th Conference on Hurricanes and Tropical Meteorology


Comparison of boundary layer profiles in Hurricanes Fabian and Isabel observed by GPS dropwindsonde and aircraft during CBLAST "stepped-descents"

Eric W. Uhlhorn, University of Miami/RSMAS, Miami, FL; and P. G. Black

Axisymmetric radial distributions of surface enthalpy and momentum fluxes are estimated from existing bulk parameterizations using high radial resolution eyewall GPS dropsonde data obtained during the CBLAST experiments in Hurricanes Fabian and Isabel (2003). Transfer coefficients used in four commonly used parameterization schemes are utilized. Nearly 300 sondes were deployed from the NOAA WP-3D aircraft during 6 flight days in the two storms. Continuous surface wind observations along the radial legs from a Stepped Frequency Microwave Radiometer (SFMR) and the UMASS Imaging Wind and Rain Atmospheric Profiler (IWRAP) were also used in the calculations. Variability among the four schemes was found to on the order of 30% for enthalpy flux estimates to over 50% for momentum flux estimates. Corresponding azimuthal variability about the radial mean was on the order of 10% and 20%, respectively.

Comparisons are made of these parameterization estimates with concurrent measurements of direct eddy correlation flux measurements by the FRD Best Atmospheric Turbulence (BAT) probe, the FRD IRGA and the RSMAS LICOR fast response humidity systems for surface winds in the 20-35 m/s range. Comparison of the parameterization estimates are also made with the budget derived flux estimates of Ramstrom and Emanuel for the eyewall mean winds ranging from 50-60 m/s. Suggestions are made for an improved flux parameterization scheme for use in coupled air-sea numerical models of hurricane intensity change.

extended abstract  Extended Abstract (72K)

Poster Session 1, Posters
Wednesday, 5 May 2004, 1:30 PM-1:30 PM, Richelieu Room

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