2011／2012年冬季中国气温异常的成因及前兆信号

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

采用国家气候中心整理的全国160站月平均气温资料、NCEP/NCAR再分析资料及NOAA全球海温资料,在探讨1986年以来中国冬季气温异常机理基础上,对2011/2012年冬季气温异常特征及其前兆信号进行分析。结果表明:地面西伯利亚高压、东亚冬季风及500 hPa乌拉尔山与贝加尔湖南侧的异常环流等系统是影响中国冬季气温的主要中高纬环流系统,而中低纬环流系统主要包括西太平洋副高环流和印缅槽。前期热带印度洋和中东太平洋关键区海温异常与后期冬季气温关联的环流系统有密切的关系:前期夏季7、8月西印度洋海温偏高时,冬季西伯利亚高压将偏强,有利于冬季风偏强和中国冬季气温偏低;而当8—10月中东太平洋海温偏高时,西太平洋副高将偏强偏大偏西,北界位置偏北,印缅槽偏强,中国气温容易偏高,反之亦然。两者对后期环流的影响存在一定的独立性,中国冬季地面气温异常是它们共同作用的结果。

Using the monthly mean temperature data of 160 stations from NCC, the NCEP/NCAR rean- alysis data and NOAA global sea surface temperature （SST） data, the causes of winter temperature a- nomaly 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 sys- tems around the Ural Mountains and the region South to the Lake Baikal at 500 hPa are the main circu- lation 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 a- nomalies of Siberian High, which makes the winter monsoon stronger and the wintertime air temperature lower in China.August, September and October SSTA of hi^her temperature over the middle and east e-quatorial Pacific mainly causes the enforcement 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 some- how independent,and the winter surface air temperature anomalies are jointly affected by the two fac- tors.