The Precipitation Hotspots of Afternoon Thunderstorms over the Taipei Basin: Idealized Numerical Simulations

Abstract

 In this study, the mechanism for precipitation hotspots (PHs) of locally developed afternoon thunderstorms in the Taipei Basin is investigated using a three-dimensional Vector Vorticity equation cloud resolving Model (VVM) with an idealized topography and surface properties. A 500-m horizontal grid resolution is used in all experiments. The results show that the local circulation is a key for PHs at the south of the Taipei Basin. The two valleys guide background southwesterly flow along with the sea breezes to penetrate into the basin. The urban heat island effect enhances the sea breeze convergence at the south of the basin and produces strong convection there. Interactions between cold pools generated by the convection and the sea breezes produce northward propagating new convective cells. Besides, the background wind direction is important in determining the location of sea breeze convergence. If the background wind direction changes from westerly to west-northwesterly, there might be no precipitation at all in the basin. This study suggests that the idealized experiments also provide a useful framework for studying the impacts of future climate change on the PHs in the Taipei Basin by applying the pseudo-global warming approach.