[A-CC25] Glaciology

[ACC25-07] Contribution of global warming on extreme snowfall in Japan

★Invited Papers

*Hiroaki Kawase¹, Yukiko Imada¹, Shun-ichi I Watanabe¹ (1.Meteorological Research Institute, Japan Meteorological Agency)

Keywords:extreme snowfall, global warming, winter monsoon, regional climate model

Snow cover is decreasing in the world and also will decrease due to global warming. In Japan, the annual maximum snow depth will decrease, especially in the coastal areas. On the other hand, Japan has cold winters with much snow in recent 10 years. Some records of heavy snowfall were broken. It is important to clarify whether global warming influences recent extreme snowfall in Japan. This study investigates impacts of historical global warming on recent extreme snowfalls in Japan. First, we focus on the heavy snowfall occurred over the Sea of Japan coast in western Japan in late December, 2021. Our results show that snowfall increased by 5 % over the inland and mountainous areas due to historical global warming. In contract, the amount of snowfall decreases over the coastal areas and ocean, where the air temperature is higher than the other areas. In these areas, the amount of rainfall increases due to atmospheric warming.

Next, we focus on the changes in the occurrence frequency of extreme snowfall due to historical global warming. The dynamical downscaling with 5-km regional climate models is conducted from the database for Policy Decision making for Future climate change. The historical experiment using sea surface temperature (SST) in 2021/22 winters shows that the frequency of heavy snowfall is higher than those in the normal years, which would be caused by the SST pattern of La Niña events. The historical and non-warming experiments shows that the frequency of heavy snowfall is enhanced by historical global warming regardless of an elevation. On the other hand, winter total snowfall increases and decreases over the lower and higher than approximately 1500 m above sea level, respectively.