Evaluating How Historical Climate Change Affected a Heavy Snowfall Event in Northern Japan in Mid‐December 2021 Using Two Pseudo Global Warming Methods

• Published in: Journal of geophysical research. Atmospheres 2024-12, Vol.129 (24), p.n/a
• Main Authors: Tamura, K., Sato, T.
• Format: Article
• Language: English
• Subjects: Air temperature; Atmospheric conditions; Climate change; Cyclones; Datasets; extratropical cyclone; Extratropical cyclones; Extreme weather; Global warming; Heavy precipitation; Heavy snowfall; Lower troposphere; Meteorological data; numerical experiment; Numerical experiments; Ocean warming; Pattern analysis; Precipitation; Pressure patterns; Sea surface temperature; Snow; Snowfall; Surface temperature; Surface wind; Troposphere; Water vapor; Water vapor transport; Water vapour; winter
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1029/2024JD041553

In mid‐December 2021, heavy snowfall occurred when an extratropical cyclone passed around Hokkaido, northern Japan. In this study, we investigated the contribution of historical climate change to the heavy snowfall event using large ensemble simulation data sets and two pseudo global warming (PGW) methods. We classified the large ensemble simulation data sets by the pressure pattern and identified the extratropical cyclone event. Composite analyses reveal that the development of the extratropical cyclone can be attributed to historical climate change. We ran the PGW method with the classified meteorological data as the input data and found that the development of the extratropical cyclone resulted in enhanced water vapor transport and intensified local convergence in the lower troposphere, causing heavy precipitation. We also found that oceanic warming made a minimal contribution to the precipitation in this event. These findings highlight the importance of considering historical changes in event‐specific synoptic‐scale atmospheric conditions when evaluating the contributions of climate change to extreme events. Plain Language Summary In mid‐December 2021, Hokkaido, located in northern Japan, experienced heavy snowfall. The results from this study indicate that the snowfall event was mainly caused by the extratropical cyclone that were intensified by historical global warming. Numerical experiments indicated that the extratropical cyclone caused regional‐scale changes in surface wind and moisture transport. Our findings highlight that, when evaluating the impact of global warming on extreme weather events such as heavy precipitation, it is necessary to consider increases in global mean air temperature and sea surface temperature and changes in the event‐specific atmospheric conditions. Key Points We used large ensemble simulation data sets and numerical experiments to investigate a heavy snowfall event in northern Japan We selected analogous cases resembling the atmospheric conditions during the snowfall event from the large ensemble simulation data sets Numerical experiments indicated that climate change had caused the development of the extratropical cyclone, resulting in enhanced snowfall