A numerical study of airflow over Taiwan island

Abstract

Two-thirds of the land mass of Taiwan island is covered by mountains that affect precipitation systems over the island. Here, we tried to understand the distribution of precipitation associated with the interaction of the prevailing wind (a northern and southern wind direction, respectively) and terrain, if the synoptic forcing was relatively small. For a northern flow under stable conditions, near surface airflow with low Froude number diverted around the Taiwan island. The relatively higher amount of rainfall occurred in the higher mountains on the upstream side, due to topographic lifting of the airflow at similar height. Along the eastern and western side of the island, rainfall occurred over the confluence area of low-level airflow. If the prevailing flow with convectively unstable air and a low Froude number was from the south, the flow was diverted near southern Taiwan and converged near northern Taiwan. Surface heating could induce an upslope flow and enhance the convergence that occurred in northern Taiwan. The upward motion associated with an upslope wind and the convergence air could help precipitation systems form along sloped areas.