Characteristics of the Extreme Low Temperature Events in China during Boreal Winter and Its Relationship to East Asian Winter Monsoon

Based on the daily minimum temperature dataset from 553 stations in China from 1961 to 2012, extreme low temperature (ELT) thresholds are determined for different stations, and occurrence frequency of ELT events during boreal winter for each station is estimated and analyzed using empirical orthogonal function (EOF). The relationship between ELT events and East Asian winter monsoon (EAWM) circulation is studied. The results suggest that the ELT events in China during the boreal winter have remarkably decreased in the past 51 years, with some spatial and temporal differences. The results of EOF analysis show that there are three main spatial modes in the ELT events in China, namely, the spatial uniformity mode, the North–South Oscillation mode, and the East–West Oscillation mode. In addition, the results of mutation test of the PC1 (the first pricipal component) series show that the abrupt change phenomenon of the occurrence frequency of ELT events during boreal winter is ubiquitous and occurred around 1986. Furthermore, the results of correlation analysis show that a good relationship was found between the frequency of ELT events and EAWM index, which may be due to the changes of the Siberian High. Besides, the results of composite analysis suggest that the abrupt change around 1986 may have something to do with the obviously southwardly movement and a weakening trend of the Siberian High.