Ocean warming pattern effects on future changes in East Asian atmospheric rivers

Abstract

Atmospheric rivers (ARs), intense water vapor transports associated with extra-tropical cyclones, frequently bring heavy rainfalls over mid-latitudes. Over East Asia, landfalling ARs result in major socio-economic impacts including widespread floods and landslides; for example, western Japan heavy rainfall in July 2018 killed more than 200 people. Using results of high-resolution atmospheric model ensemble simulations, we examine projected future change in summertime AR frequency over East Asia. Different sea surface temperature (SST) warming patterns derived from six atmosphere-ocean coupled model simulations were assumed to represent uncertainty in future SST projections. The rate of increase in the frequency of landfalling ARs over summertime East Asia is on average 0.9% K-1 and is dependent on SST warming patterns. Stronger warming over the North Indian Ocean and South China Sea or weaker warming over the tropical central Pacific produce more frequent landfalling ARs over East Asia. These patterns are similar to the co-variability of SST, atmospheric circulation, and ARs over the western North Pacific found on the interannual time scale. The results of this study suggest that the natural disaster risk related to landfalling ARs should increase over East Asia under global warming and SSTs over the Indo-Pacific region holds the key for a quantitative projection.