26th Conference on Hurricanes and Tropical Meteorology


Roll vortices in the hurricane boundary layer


Ian Morrison, University of Hawaii, Honolulu, HI; and S. Businger, F. Marks, and P. Dodge

Doppler velocity data from the WSR-88D radar during four hurricane landfalls are analyzed to investigate the presence of organized vortices in the hurricane boundary layer. The wavelength, depth, magnitude, and track of velocity anomalies were compiled through analysis of Doppler velocity data. The analysis reveals alternating bands of enhanced and reduced azimuthal winds that are closely aligned with the mean wind direction. Resulting statistics provide compelling evidence for the presence of organized secondary circulations or boundary layer rolls in hurricanes. Momentum fluxes associated with the secondary circulations are estimated using the covariance between the horizontal and vertical components of the wind fluctuations in rolls, with resulting fluxes 2-3 times greater than estimated by parameterizations in numerical weather prediction models. The observed prevalence of such vortices has significant implications for the vertical transport of energy in hurricanes, for the character of wind damage, and for improvements in numerical simulations of hurricanes.

The observed results above are compared to a Large Eddy Simulation (LES) model run with hurricane dynamic and thermodynamic initial conditions.

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

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