Extended Abstract (204K)10D.6
Tropical cyclone near-core radial structure from aircraft observations: Implications for vortex resiliency
Kevin J. Mallen, University of Hawaii at Manoa, Honolulu, HI
Recent theoretical studies, based on vortex Rossby wave (VRW) dynamics, have established the importance of the radial structure in the response of tropical cyclone (TC)-like vortices to ambient vertical wind shear. In essence, the VRW theory predicts that the degree of vortex broadness in the near-core region beyond the radius of maximum wind (RMW) determines whether a tilted TC-like vortex will realign and resist vertical shear or continue to tilt over and shear apart. Numerical simulations have indeed demonstrated that the vortex resiliency is sensitive to the initial specification of the idealized vortex. This brings into question how well the true nature of TC structure is represented by idealized vortices that are commonly used in some theoretical studies.
In this paper we re-examine the swirling wind structure of TCs by utilizing flight-level observations collected from Atlantic and eastern Pacific storms during 1977-99. Hundreds of radial profiles of azimuthal-mean tangential wind and relative vorticity are calculated and compared with some standard idealized vortex profiles. Our comprehensive analysis reaffirms that real TC structure is characterized by a relatively slow tangential wind decrease outside the RMW and a corresponding skirt of cyclonic relative vorticity possessing a negative radial gradient. This observed vortex broadness is conspicuously absent in many idealized vortices frequently used in theoretical studies of TC evolution. Implications of these results will be discussed.
Session 10D, tropical cyclone observations and structure V
Wednesday, 5 May 2004, 10:15 AM-11:45 AM, Napoleon III Room
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