Subseasonal mode of cold and wet climate in South China during the cold season: a climatological view

Abstract

The authors investigate the dominant mode of climatological intraseasonal oscillation (CISO) of surface air temperature (SAT) and rainfall in China, and discuss the linkage of cold and wet climate in South China (SC) with the Arctic circulation regime during the cold season (from November to March). Results show that a positive CISO displays a cold-dry climate in North China, whereas a cold-wet pattern prevails in SC with a quasi-30-day oscillation during the peak winter season. In SC, the intraseasonal variability of SAT plays a leading role, altering the cold-wet climate by the southward shift of a cold front. Evidence shows that the circulation regime related to the cold and wet climate in SC is mainly regulated by a pair of propagating ISO modes at the 500-hPa geopotential height in the negative phase of Arctic Oscillation. It is demonstrated that the local cyclonic wave activity enhances the southward movement of the Siberian high, favoring an unstable atmosphere and resulting in the cold-wet climate over SC. Therefore, the cold-air activity acts as a precursor for subseasonal rainfall forecasting in SC.