Tropical cyclone and extreme rainfall trends in East Asian summer monsoon since mid-20th century

Proper interpretations of extreme rainfall trends in the Asian monsoon regions are complicated by tropical cyclones (TCs) from tropical oceans, whose rainfall trend may be different from the local monsoon (non-TC) rain. Here we show that the trends over the China summer monsoon region have been distorted by western North Pacific typhoons, which bring rainfall with decreasing frequency and increasing intensity. Typically the latter is not sufficient to overcome the former, so TC-related extreme rainfall trend is smaller than monsoon-related extreme rainfall. The net impact underestimates the increasing trend and overestimates the decreasing trend in monsoon extreme rainfall over most areas. The effect is minimal in the Meiyu rain belt region, but reaches 30% in northeastern and southern China. The largest distortions occur on offshore islands in the main TC paths that underwent significant decadal variations. In Hainan, the -3%/decade trend becomes +7%/decade if typhoon rainfall is removed. An opposite case occurs in Taiwan, where the extreme rainfall trend is hugely inflated by local increases in TC rainfall. These opposite effects emphasize the importance of considering the different mechanisms of rainfall systems in order to avoid mis-attribution of regional effects on extreme rainfall to thermodynamic consequences of global warming. Citation: Chang, C.-P., Y. Lei, C.-H. Sui, X. Lin, and F. Ren (2012), Tropical cyclone and extreme rainfall trends in East Asian summer monsoon since mid-20th century, Geophys. Res. Lett., 39, L18702, doi:10.1029/2012GL052945.