Heavy Snowfall Has Already Been Enhanced by Anthropogenic Global Warming in Japan

抄録

Large-ensemble experiments with global and regional climate models enable us to assess changes in the risks of local-scale heavy snowfall due to anthropogenic global warming. We conduct 100-ensemble historical and non-warming global climate experiments forced by oceanic conditions in 2021/22 when La Niña phenomena occurred, and conduct dynamical downscaling using regional climate models with 20 km and 5 km grid intervals. The 10-year return values of total winter snowfall decrease in most of Japan due to anthropogenic global warming, while they increase at high elevations and the northern parts of Japan. The winter-maximum daily snowfall is enhanced not only over high elevations but also over low elevations in Japan. Tsunan Town is located in an inland area of central Japan where the winter-maximum daily snowfall is enhanced by anthropogenic global warming. Composite analyses of winter-maximum daily snowfall events at the Tsunan weather station indicate that the enhancement of daily snowfall due to anthropogenic global warming is related to deeper troughs at 500 hPa and warmer and more humid air in the lower atmosphere in the historical 2021/22 winter than those in the non-global-warming 2021/22 winter.