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2018/03/13 14:00 Dr. Yi-Chih Huang（Research Center for Environmental Changes, Academia Sinica）
Seminar
Poster： ╱ Post date：2018-03-06NCU IHOS Seminar Announcement
Speaker：Dr. Yi-Chih Huang
Place：S-325, Science Building 1
Abstract：
Title：Looping tracks associated with tropical cyclones approaching an isolated mountain. Part I: Essential parameters
Speaker：Dr. Yi-Chih Huang
Research Center for Environmental Changes, Academia Sinica
Time：3/13（Tue.）14：00
Place：S-325, Science Building 1
Abstract：
Essential parameters for making a looping track when a westward-moving tropical cyclone (TC) approaches a mesoscale mountain are investigated by examining several key nondimensional control parameters with a series of systematic, idealized numerical experiments, such as U/Nh, Vmax/Nh, U/fLx, Vmax/fR, h/Lx, and R/Ly. Here U is the uniform zonal wind velocity, N the Brunt-Vaisala frequency, h the mountain height, f the Coriolis parameter, the maximum tangential velocity at a radius of from the cyclone center and Lx is the halfwidth of the mountain in the east-west direction. It is found that looping tracks (a) tend to occur under small U/Nh and U/fLx, moderate h/Lx, and large Vmax/Nh, which correspond to slow movement (leading to subgeostrophic flow associated with strong orographic blocking), moderate steepness, and strong tangential wind associated with TC vortex; (b) are often accompanied by an area of perturbation high pressure to the northeast of the mountain, which lasts for only a short period; and (c) do not require the existence of a northerly jet. The nondimensional control parameters were consolidated into a TC looping index (LI), which was tested by several historical looping and non-looping typhoons approaching Taiwan’s Central Mountain Range (CMR) from east or southeast. It was found that LI < 0.0125 may serve as a criterion for looping track to occur.
Last modification time：2018-03-06 PM 3:45
