Variations of the sum of extreme cold and warm days over China in winter dominated by North Atlantic Meridional overturning circulation

This study is led by Professor Zhiyan Zuo (Department of Atmospheric and Oceanic Sciences, Fudan University).

Winter temperature extremes received public attention due to their serious impacts on living creatures and ecosystems, as well as human society. IPCC AR6 has concluded that anthropogenic global warming is the dominant factor for the increases in warm extremes and the decrease in the likelihood of cold extremes. A long-term increasing frequency of warm extremes and decreasing cold extremes were also observed over China during boreal winter along with global warming. However, Professor Zuo found that the sum of the widespread extreme cold days and warm days over China exhibits obvious decadal variation, quite different from global warming. That means, global warming can influence the ratio of the extreme cold days and warm days, but little influence the total frequency of the extreme temperature events.

Which factors dominate the total frequency of the extreme temperature events over China? AMOC is an important driver of the change of atmospheric thermal state in the Northern Hemisphere winter. Prof. Zuo investigated the relation of AMOC to the sum of extreme cold and warm days and found the two exhibited similar decadal variations. The investigation on the relevant physical process suggested that the Siberia High is the bridge linking the AMOC to the extreme temperature events over China. Nevertheless, the relationship between the AMOC, the Siberia High and the extreme cold and warm days is bound to be closely related to the Ural blocking high, East Asian Trough and westerly belt. The physical process for the influence of the AMOC on the occurrence frequency of the widespread extreme cold and warm days is quite complex and needs to be investigated further. Professor Zuo and her research team are working on it now.

See the article:

Zuo Z, Li M, An N, Xiao D. 2022. Variations of widespread extreme cold and warm days in winter over China and their possible causes. Science China Earth Sciences, 65(2): 337–350, https://doi.org/10.1007/s11430-021-9836-0

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