Dynamical downscaling simulation and future projection of summer rainfall in Taiwan: Contributions from different types of rain events

Summer rainfall in Taiwan is composed of four types of rain events: tropical cyclone (TC), frontal convection (FC), diurnal convection (DC), and other southerly convection (SC) that propagates from the nearby ocean. In this study, we accessed the present-day simulation (1979-2003) and future projection (2075-2099, the Representative Concentration Pathway 8.5 scenario) of rainfall in Taiwan by using the regional Weather Research and Forecasting model driven by the global High Resolution Atmospheric Model. The results indicated that the dynamical downscaling process adds value to the present-day simulation of summer rainfall in Taiwan and the contribution of different types of rain events. It was found that summer rainfall in Taiwan will increase in a warmer future and that this change was mainly due to an increase in SC rainfall (i.e., light rainfall event). The following trends in Taiwan rainfall were also predicted in a warmer future: (1) SC rainy days will increase because the intensified monsoonal flow facilitates the propagation of more SC toward Taiwan, (2) TC rainy days will decrease as the Western North Pacific subtropical high extends southwestward and prevents TC systems from passing over Taiwan, (3) DC rainy days will decrease in response to the increased local thermal stability, and (4) FC rainy days will show no significant changes. Moreover, all types of rainfall are projected to become more intense in the future due to the increased moisture supply in a warmer climate. These findings highlight how the rainfall characteristics in East Asia may change in response to climate change.