西南地区冬季气候异常的时空变化特征及其影响因子

The Spatio-temporal Variation of Winter Climate Anomalies in Southwestern China and the Possible Influencing Factors

利用1961-2010年的多种观测资料,对西南地区冬季气候异常的时空演变特征及其影响因子进行了分析。结果表明:西南地区冬季气温变化主要存在全区一致和东、西部反位相两种模态,这两种模态均存在显著的年代际变化。全区温度的一致变化与东亚冬季风的异常有关,东、西反位相的变化与西太平洋副热带高压和冷空气的异常活动有关。冬季降水异常主要表现为全区一致的变化特征。北半球环状模(NAM,AO)和ENSO对西南地区气温没有显著的影响。当NAM偏强(弱)时,西南地区降水偏多(少)。ElNio年,西南地区降水一致偏多;LaNia年,西南地区中部降水偏多,东、西部降水偏少。2010年冬季西南地区的干旱更有可能是由NAM异常引起的,而不是ElNio。

The impacts of winter extreme climate events in recent years on socio-economy indicated that the importance of winter climate anomalies is the same as its summer counterpart in southwestern China（SWC）.The spatio-temporal variations and its possible causes of climate anomalies in SWC were investigated by utilizing observation data from 1961 to 2010.The results indicate that surface air temperature anomalies in SWC have two dominant modes,one is homogenous,the other is dipole in latitudinal direction.The former was caused by the anomalies of East Asian winter monsoon,the latter arose from the anomalies of both subtropical west Pacific high and regional cold air in lower troposphere.The most dominant mode of precipitation anomalies in SWC is homogenous and it has a high correlation with northern hemisphere annular mode（NAM,AO）.NAM and ENSO did not have significant impacts on the variation of surface air temperature in SWC.The anomalies of NAM would lead to the anomalies of tropical circulations.When NAM is in positive（negative） phase,the winter precipitation is more（less） than normal in SWC.Precipitation in the whole SWC increased during El Nio winter,but increased in central SWC,and decreased in west and east of SWC during La Nia winter.The severe drought in SWC in the winter of 2010 is more likely caused by anomalies of NAM instead of El Nio.