Idealized simulations of the effect of local and remote topographies on tropical cyclone tracks

Abstract

This is the second part of a study on the effect of topography on tropical cyclone (TC) tracks. In Part I, idealized simulations using the Weather Research and Forecast (WRF) Model were conducted with artificial TCs inserted at a location such that they make landfall on the central part of Taiwan and the Luzon. In this second part, the effects of local and remote topographies are studied by examining the tracks of several TCs approaching Taiwan at different latitudes. Tropical cyclones approaching to the south of Taiwan (remote effect) slow down and are first deflected southwestward and then northward. Moreover, a sharp northward deflection occurs for a TC passing further south of Taiwan, but the deflection is small for a TC passing further north of Taiwan. In the presence of China's terrain, an additional larger but weaker anticyclonic gyre is induced so that the TC is affected, even when it is further away from the land. The flow associated with this gyre reduces the northward deflection caused by the Taiwan terrain but enhances the southwestward shift of the TC. However, no cyclonic gyre is found over inland China if the TC is far away from China's coast, probably because of the irregular elevated topography. For TCs making landfall on South China, a westward shift is found just prior to landfall, which is more significant if the height of China's terrain is doubled. This westward shift can be explained by the horizontal advection, vertical advection and diabatic heating terms in the potential‐vorticity tendency equation.