27th Conference on Hurricanes and Tropical Meteorology


Direct Airborne Measurements of Momentum Flux in Hurricanes

Jeffrey R. French, NOAA/OAR/ARL, Oak Ridge, TN; and W. M. Drennan, J. A. Zhang, and P. G. Black

An important outcome from the ONR-sponsored Coupled Boundary Layer Air-Sea Transfer (CBLAST) Hurricane Program is the first ever direct measurements of momentum flux from within hurricane boundary layers. In 2003, a specially instrumented NOAA P3 aircraft obtained measurements suitable for computing surface wind stress and ultimately estimating drag coefficients in regions with surface wind between 20 and 32 m/s. Analyses of data from forty-two flux legs flown within 400 m of the surface in two storms are presented. Our results indicate a roll-off in the drag coefficient at higher wind speeds, in qualitative agreement with laboratory and modeling studies and inferences of drag coefficients using a log-profile method. However, the amount of roll-off and the wind speed at which the roll-off occurs remains highly uncertain underscoring the need for additional measurements.

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Session 9C, Special Session: CBLAST HURRICANE II
Wednesday, 26 April 2006, 1:30 PM-3:05 PM, Regency Grand BR 1-3

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