Atmospheric River Influences on Extreme Rainfall in Taiwan

Taiwan receives large amounts of heavy and extreme rainfall during its Mei-Yu season. In this study, we assess the contribution of atmospheric rivers (ARs) to Mei-Yu rainfall using a west Pacific AR dataset constructed by an automated AR detection tool (ARDT, Wick et al 2013). We find that the majority (~80%) of extreme rainfall during Mei-Yu season is due to ARs, primarily associated with two regions of high AR density to the northwest and southeast of Taiwan. Though the northwest ARs are more frequent, the southeast ARs produce more extreme rainfall and are associated with greater moisture flux convergence. Moreover, southeast ARs exhibit a marked increase in extreme rainfall starting in the early 1990s. Using ARDT output and ERA-5 data, we construct a climatology of these AR events and examine the synoptic causes of an increase in these impactful southeast AR events. Representative case studies of the two AR types are used to illustrate the typical evolution of these events in greater detail.