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Possible influence of Asian polar vertex contraction on rainfall deficits in China in autumn


Dynamics of Atmospheres and Oceans


Xian Zhua,Zhigang Wei,Wenjie Dong,Zhenchao Li,Zhiyuan Zheng,Chen Chen,Guangyu Chen,Yajing Liu








Corresponding Author

Wei, ZG

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Asian polar vertex contraction; Rainfall deficit; Autumn; China


The mechanisms governing variations in autumn precipitation are complicated and influenced by a number factors. This paper analyses the characteristics of autumn precipitation in China and investigates the influence of Asian polar vertex contraction on rainfall deficits in China and relevant mechanisms. Autumn precipitation decreased significantly from 1961 to 2012 in mid- and southern China, and the area of the Asia polar vortex (AAV) has decreased significantly since 1988. Asian polar vertex contraction is found to be an important factor in these autumn rainfall deficits in China through the following mechanism. Asian polar vertex contraction causes anomalously high geopotential heights in East Asia (from 25 N to 55 N) and low heights north of 65 N in the upper and lower troposphere, weakening meridional gradients in geopotential height. In the upper troposphere, the westerly and northerly winds are strengthened over high latitudes and westerly winds and the subtropical westerly jet are weakened over the East Asian mid latitudes. In the lower troposphere, westerly winds are strengthened over high latitudes, westerly winds are weakened in East Asia and along the southern periphery of the Tibetan Plateau, and northerly winds in mid- and southern China are clearly strengthened. Hence, autumn rainfall decreases in mid- and southern China.