Extended Abstract (844K)8A.6
WSR-88D Observations of Boundary Layer Rolls during Hurricane Landfall
Ian J. Morrison, University of Hawaii, Honolulu, HI; and F. D. Marks and S. Businger
This study uses WSR-88D radar data to explore the structure of the hurricane boundary layer (BL) during landfall. Specifically, we will examine BL rolls that appear in the Doppler residual velocity display. The WSR-88D in precipitation-mode completes a volume scan, composed of 360 scans at 14 elevation angles from 0.5 -19.5, in 6 minutes. The mean radial velocity of each scan is a sine function of azimuth angle. The amplitude and phase of this sine curve are measures of the wind speed and direction at the scan elevation. Also, a Fourier analysis of the locity-Azimuthal Display (VAD) permits the estimation of divergence, wind speed and direction. Using this analysis to create a mean radial velocity, then subtracting this mean from the actual Doppler velocity, gives the residual velocity. Given the location and elevation of the radar site, the BL roll dimensions, intensity, and motion can be identified in the residual velocity display. Hurricanes Fran (1996), Bonnie (1998), and Georges (1998) were examined using the WSR-88Ds from Wilmington, N.C., Morehead City, N.C., and Key West, respectively. We will present a statistical analysis of BL rolls in the three hurricanes and their implications in the hurricane environment. We are also using NCARs large eddy simulation (LES) to model the BL rolls and will present and discuss preliminary results.
Session 8A, Tropical Cyclones at Landfall (Parallel with Session 8B, 8C, and 8D)
Wednesday, 1 May 2002, 8:30 AM-10:45 AM
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