Graphical Abstract

Yokoyama, C., H. Tsuji, and Y. N. Takayabu, 2020: The effects of an upper-tropospheric trough on the heavy rainfall event in July 2018 over Japan. J. Meteor. Soc. Japan, 98, 235-255.
Special Edition on Extreme Rainfall Events in 2017 and 2018 Abstract with highlights

Plain Language Summary: Heavy rainfall occurred over a broad portion of western Japan on July 5–8, 2018. We found that the heavy rainfall was brought by a well-organized rainfall system, which was maintained under relatively stable and very humid conditions compared with the climatology. An upper-tropospheric trough, which lingered around the Korean Peninsula, played an important role in producing the humid stratification. By examining dynamical ascent associated with the trough and diabatic ascent separately, we found that dynamical ascent helped to moisten a relatively deep layer of the mid- to lower troposphere in conjunction with southerly horizontal moisture flux.