Features and Possible Causes for the Low Temperature in Winter 2011/2012

During the winter(December 2011—February 2012),the surface air temperatures were below normal in most China,and the mean temperature in China was—4.8℃,being the coldest winter since 1986.The extreme low temperature climate events were prevailed in China such as the extremes of daily temperature drop(DTD),which were observed in Inner Mongolia,Xinjiang,Xizang and Shaanxi.The possible cause for the extreme low temperatures in China was investigated by using the conventional observational temperatures and NCEP reanalysis datasets.The results have shown that the strong East Asian winter monsoon might be responsible for occurrence of extreme low temperatures,with dominating of anomalous cold high pressure system over the Siberian Plain,persistence of blocking system over the Ural Mountains and Baikal Lake,and deeper than normal East Asian major trough.Further analysis shows that La Nina might cause thp abnormally stronger East Asian winter monsoon.