To investigate future changes in snow cover and snowfall over mountainous areas in central Japan, we conducted regional climate projections using a high-resolution non-hydrostatic regional climate model (NHRCM) with 5 km and 1 km grid spacings. Boundary conditions are derived from the database for Policy Decision making for Future climate change (d4PDF) 20 km regional climate projections (d4PDF20). The d4PDF20 assumes two future climates when global mean surface air temperatures are approximately 2 K and 4 K warmer than in the preindustrial period. Experiments with 5 km grid spacing are conducted by NHRCM for 372 years in d4PDF20 in each climate. Experiments with 1 km grid spacing are performed focusing on 5 years with heavy, median, and light snow cover of mountainous areas in each climate. In the years with heavy snow cover in 2 K and 4 K warming climates, snowfall is enhanced from late December to February at more than 2000 m above sea level (mASL) in the northern parts of Japan’s Northern Alps, resulting in heavy snow cover comparable to that in the present climate. Heavy daily snowfall remarkably increases due to global warming in the years with heavy snow cover. At low elevations below 500 mASL, snowfall decreases in all ranges of snowfall intensity in the 4 K warming climate, while the frequency of heavy daily snowfall increases in the 2 K warming climate. Precipitation is enhanced around the Japan-Sea Polar-airmass Convergence Zone and the mountainous area facing the Sea of Japan, resulting in strengthened heavy snowfall at high elevations where the winter mean temperature is approximately − 10 °C in the present climate. On the other hand, remarkable reductions in snow cover and snowfall are projected in years with light snow cover. Our results indicate that global warming causes heavy and light mid-winter snowfalls at high elevations of Japan’s Northern Alps that are more extreme than those in the present climate.

Graphical abstract

中文翻译：

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由于日本中部高山地区的全球变暖，冬季极寒和轻雪的变化

为了调查日本中部山区的积雪和降雪的未来变化，我们使用高分辨率非静水区域气候模型（NHRCM）进行了区域气候预测，该模型的网格间距为5 km和1 km。边界条件来自未来气候变化政策决策数据库（d4PDF）20 km区域气候预测（d4PDF20）。d4PDF20假设未来两个气候条件是全球平均地面气温比工业化前时期高2 K和4K。NHRCM在d4PDF20中在每种气候下进行了372年5 km网格间距的实验。以每公里1公里的网格间距进行实验，重点是在每种气候下山区的大雪，中雪和小雪覆盖5年。在2 K和4 K变暖气候下有大雪覆盖的年份中，从12月下旬到2月，日本北阿尔卑斯山北部地区的海拔超过2000 m（mASL）的降雪量增加，导致可比的大雪覆盖在目前的气候下 由于多年来积雪覆盖，多年来全球变暖，每天的大雪量显着增加。在低于500 mASL的低海拔处，在4 K变暖的气候中，降雪在所有降雪强度范围内都会降低，而在2 K变暖的气候中，每天大降雪的频率会增加。日海极地气团汇聚区和面向日本海的山区的降水增加，导致高海拔地区的降雪量增加，在当前气候下，冬季平均温度约为− 10°C。另一方面，预计在小雪覆盖的情况下，积雪和降雪量将显着减少。我们的结果表明，全球变暖在日本北阿尔卑斯山的高海拔地区造成了大雪和中秋降雪，这比当前气候下的降雪更为极端。

图形概要