Causes and precursors of the winter temperature anomaly in China in 2011 /2012

Using the monthly mean temperature data of 160 stations from NCC,the NCEP /NCAR reanalysis data and NOAA global sea surface temperature( SST) data,the causes of winter temperature anomaly and its precursors in 2011 /2012 are analyzed on the basis of associated mechanisms since 1986. The results show that the Siberian High,East Asian winter monsoon and the abnormal circulation systems around the Ural Mountains and the region South to the Lake Baikal at 500 hPa are the main circulation systems at high latitudes which exert important impact on the wintertime surface air temperature in China; the circulation systems at low latitudes mainly include the Western Pacific Subtropical High and the India-Burma Trough; the sea surface temperature anomalies( SSTA) of key regions in tropical Indian Ocean and the middle-east equatorial Pacific are closely related to the circulation system variation associated with the winter temperatures in late winter. The July and August SSTA of higher temperature in the western Indian Ocean mainly corresponds to the enforcement of winter circulation anomalies of Siberian High,which makes the winter monsoon stronger and the wintertime air temperature lower in China. August,September and October SSTA of higher temperature over the middle and east equatorial Pacific mainly causes the en-forcement of Western Pacific Subtropical High and India-Burma Trough. The location of Western Pacific Subtropical High is to the west and north,and the India-Burma Trough becomes stronger at the same time,which causes the temperature in China to be warmer,and vice versa. The influences of the SSTA in these two key regions on the subsequent circulation are somehow independent,and the winter surface air temperature anomalies are jointly affected by the two factors.