Future Enhancement of Heavy Rainfall Events Associated with a Typhoon in the Midlatitude Regions

抄録

In August 2016, eastern Hokkaido in northern Japan had unusual typhoon landfalls and experienced heavy rainfall events that caused severe disasters. To understand the impact of global warming on typhoon-related rainfall in such midlatitude regions, numerical experiments on one of the typhoons in August 2016, Typhoon Chanthu, were conducted by using a high-resolution three-dimensional atmosphere–ocean coupled regional model in current and pseudo-global warming (PGW) climates. The amount, intensity, and duration of rainfall in eastern Hokkaido associated with the typhoon increased in the warming climate. The PGW typhoon traveled northward with relatively slower translation speed and resulted in a delay in the landfalls for 6 h. Furthermore, large amounts of near-surface water vapor > 22 g kg⁻¹ from the southern sea increased the convective instability around eastern Hokkaido and caused tall and intense updrafts. As a result, significant predecessor rainfall events with intense rainfall developed about 24 h before the typhoon landfall. Increased near-surface water vapor in the warming climate also enhanced rainfall associated with the typhoon passage over a widespread area. These results suggest that attention should be paid to future enhancement of heavy rainfall events in the midlatitude regions under global warming.