Publication Date:
2015-09-30
Description:
This is the third part of a study on the effect of topography on tropical cyclone (TC) tracks. In previous parts, idealized simulations were conducted using the Weather Research and Forecasting model to study the underlying mechanisms for the upstream northward deflection of a TC and the local and remote topography effects. The initial TC size was the same in all these simulations. In this third part, the track deflections of TCs with different sizes are investigated. As in the two parts, the simulations are made on a beta plane with no background flow. For a TC approaching Taiwan (TW), there is an apparent optimal TC size with the largest northward deflection. However, an appreciable track deflection is only found for smaller TCs approaching TW directly. In addition, as might be expected, the onset location of the northward deflection is closer to TW for smaller TCs. Moreover, the contribution from diabatic heating is opposite to that from horizontal advection (HA) in the potential vorticity tendency (PVT) calculation due to the vertical wind shear induced by the terrain-induced gyres although HA is still the dominant term in the PVT equation. A southward deflection on the eastern side of TW is found in some smaller TC cases. A looping track occurs for a medium-size TC approaching central TW and a V-shape track is found for a small-size TC approaching northern TW. Among the cases, some similarities can be found. First, the gyre-flow becomes weak so that the TC is slowed down. Second, an individual cyclonic gyre is found on the southeastern side of TW so that the TC is deflected westward and then southward. Third, another newly-generated gyre pair pushes the TC northward after the southward deflection.
Print ISSN:
0035-9009
Electronic ISSN:
1477-870X
Topics:
Geography
,
Physics
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