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Researchers at University of Tsukuba and the Meteorological Research Institute have identified how atmosphere-ocean interactions in the midlatitudes reinforce the East Asian winter monsoon (EAWM). During strong monsoon seasons, cold air outbreaks from the Eurasian continent cool the midlatitude western North Pacific (WNP). This oceanic cooling, in turn, alters atmospheric circulation in a manner that further intensifies the monsoon. The results underscore the importance of midlatitude feedback processes in driving winter climate variability over East Asia and provide insights that may improve the prediction of extreme weather events and enhance seasonal forecasting.

Tsukuba, Japan—A strong EAWM often produces severe cold spells and heavy snowfall in Japan, disrupting daily life and economic activity. While the impacts of tropical variability, such as El Niño and La Niña, on the monsoon have been extensively examined, the influence of the midlatitude ocean has been less well understood.

Using long-term observational datasets and atmospheric model simulations, the study shows that strong monsoon conditions enhance upward heat fluxes over the midlatitude WNP, progressively cooling sea surface temperatures (SSTs) south of Japan. These cold SST anomalies modify storm-track activity and strengthen a cyclonic circulation east of Japan, which, in turn, intensifies the cold continental outflow. Thus, a feedback loop emerges: cold air cools the ocean, and the cooled ocean further reinforces the monsoon.

These results highlight the critical role of midlatitude atmosphere-ocean coupling in controlling winter climate variability over East Asia and provide new insight into the mechanisms driving extreme winter events, including cold surges and heavy snowfall. They also offer potential pathways for improving seasonal prediction.

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This work was supported by the Japan Society for the Promotion of Science (JSPS) through Grants-in-Aid for Scientific Research JP24H02228, JP24H02223 (on Transformative Research Areas 24A203), JP24K07140, JP23K20542, JP24H02193, JP24K00705, and JP23K20901, and by the Environmental Restoration and Conservation Agency through Environment Research and Technology Development Fund JPMEERF20242001.

Original Paper

Title of original paper:

Midlatitude Atmosphere-Ocean Interaction Reinforces the East Asian Winter Monsoon

Journal:

Geophysical Research Letters

DOI:

10.1029/2025GL118566

Correspondence

Professor UEDA Hiroaki
Institute of Life and Environmental Sciences, University of Tsukuba

Senior Researcher TAKAYA Yuhei
Meteorological Research Institute, Japan Meteorological Agency

Related Link

Institute of Life and Environmental Sciences