Extended Abstract (232K)13D.2
Tropical Cyclone Structure and Track Changes Prior to Landfall
Martin L. M. Wong, City University of Hong Kong, Hong Kong, China; and J. C. L. Chan
This paper presents results of a numerical study on possible changes in tropical cyclone (TC) structure and track as it approaches land. The model is based on the MM5 with triply nested 45-15-5 km domains. The basic initial configuration is a well-developed vortex at a certain distance from “land”, which is defined as a region with a larger roughness and no moisture flux. In the first experiment, run on an f plane and without any background flow, the vortex is found to be “attracted” towards land. The displacement of the vortex is not linear, but in the form of looping motion. The closer the vortex is to the land, the faster is the mean displacement speed of the vortex and the larger is the loop. A horizontal symmetry is found in the potential vorticity (PV) distribution, which leads to different advection patterns. Together with the asymmetries in heating, the resultant PV tendency generally gives the instantaneous motion of the vortex. The structure of the vortex is also found to be different, with strong asymmetries in the wind and thermodynamic fields. Two other sets of experiments have been carried out: (i) running the same experiment but on a beta plane, and (ii) imposing a uniform flow to advect the vortex towards the land for both f and beta planes. Results of these experiments and the physical processes involved will be presented at the conference.
Session 13D, Tropical cyclones at landfall II
Thursday, 6 May 2004, 10:15 AM-11:45 AM, Napoleon III Room
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