Extended Abstract (248K)13A.2
Tropical Cyclone Intensity Change in A Uniform Flow
Joey H. Y. Kwok, City University of Hong Kong, Hong Kong, China; and J. C. L. Chan
Most of the studies on tropical cyclone (TC) intensity change focus on the effect of vertical wind shear. One of the proposed physical processes is the horizontal asymmetry generated as a result of the vertical wind shear. This paper therefore attempts to study, based on a numerical model, the more fundamental problem of the effect on TC intensity change due to horizontal asymmetry caused by horizontal shear. The study begins with a simple uniform flow imposed on a cyclonic vortex (which effectively creates a horizontal wind asymmetry). It is found that the vortex does not intensify as much as one without any background flow, even on an f plane. The reduction in the amount of intensification also depends on the vortex intensity prior to the imposition of the flow, with a stronger initial vortex being affected less. On a beta plane, the vortex actually weakens, and the weakening is accelerated with the imposition of a uniform flow. This accelerated weakening depends on the direction of the flow, with easterly flow having a greater effect. Preliminary analyses indicate that such changes in intensity result from the wind asymmetries that lead to asymmetries in the angular momentum import/export. Other results on the effect of a horizontally-sheared flow will be presented at the conference.
Session 13A, Tropical Cyclone Intensity Change II: Environmental Factors
Thursday, 6 May 2004, 10:15 AM-11:45 AM, Le Jardin Room
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