以多組海溫變異推估臺灣梅雨季極端 降雨的未來變化

In Taiwan, long-term statistical analysis suggests that extreme rainfall occurred in May and June (i.e., the Mei-Yu season) frequently dangers people's lives and causes economic losses. To understand possible impacts of extreme rainfall in Taiwan during the Mei-Yu season under future climate change, this study uses dynamical downscaling simulations driven by a high resolution global model to project the differences of extreme rainfall in Taiwan between two time periods: the end of 21st century (2076~2099; under RCP8.5 scenario) and the present (1980~2003; Historical). The analyses focus on the differences of projected changes in extreme rainfall over four major sub-regions of Taiwan (including northern, central, southern and eastern Taiwan). For the future projection, this study uses four different groups of sea surface temperature changes proposed by Mizuta et al. (2014) as the boundary conditions to drive the models. From the ensemble mean of the multiple future projections, it is noted that extreme rainfall in most sub-regions of Taiwan (including northern, central and southern Taiwan) will become more frequent and more intense by the end of 21^st century, as compared to the present. For east Taiwan, the extreme rainfall is projected to be more frequent in the future, but the related change in extreme rainfall intensity is not clear. Among the four sub-regions, southern Taiwan is the region that will have the most significant increase in both intensity and frequency of extreme rainfall in the future as compared to the present. It is suggested that the projected increase in extreme rainfall activities in southern Taiwan is related to the projected increase in large-scale westerly wind, which brings more water vapor and leads to increase in wind convergence over the windward side of Taiwan.