Impact of historical and future warming on heavy rainfall over eastern Japan induced by Typhoon Hagibis (2019) in dynamical downscaling simulations

To investigate the impact of historical and future warming on heavy rainfall induced by Typhoon Hagibis (2019), we conducted control (CTL), pseudo-non-global-warming (PNGW), pseudo-moderate-global-warming (PGW2), and pseudo-extreme-global-warming (PGW4) runs using an identical regional atmospheric model. Total rainfall in the Kanto/Tohoku regions changed by − 7%/− 6%, + 3%/+ 12%, and + 9%/+ 23% in the PNGW, PGW2, and PGW4 runs, respectively, with respect to that in the CTL run. The regional differences in total rainfall changes originated from Hagibis' precipitation systems under warming climates. Global warming led to a well-developed convectively unstable layer and a humid state in the middle troposphere north of Hagibis through an increase in northward moisture transport around Hagibis. More moist and unstable conditions in the middle troposphere contributed to increased precipitation in the western-to-northern sectors of Hagibis, where the outer-rainband was unclear in the CTL run, leading to the formation of a strong convective outer-rainband of Hagibis under a future warmed climate. The widespread and intense outer-rainband expanded the heavy rainfall area over the Kanto/Tohoku regions by − 6%/− 10%, + 5%/+ 24%, and + 13%/+ 54% in the PNGW, PGW2, and PGW4 runs, respectively, with respect to that in the CTL run, suggesting that the increase in Hagibis-related flooding risks in response to a warming climate is greater in Tohoku than in Kanto.