东亚冬季气温的年际变化特征及其与海温和海冰异常的关系

Interannual Variations of Winter Temperature in East Asia and Their Relationship with Sea Surface Temperature and Sea Ice Concentration

通过谐波分析的方法,对东亚31个冬季(1980—2010年)的气温提取年际变化分量(周期小于8a部分)进行EOF分析。结果发现:在年际变化的时间尺度上,东亚冬季气温表现为高纬模态和低纬模态2个主要模态,它们一起可以解释总方差73%的变化。进一步分析表明,在年际变化尺度上,与气温变化的高纬模态相联系的大气环流表现为显著的北极涛动(AO)负位相分布,海平面气压场上西伯利亚高压和阿留申低压北移,对流层中层东亚大槽西移,高层西风急流向西北方向移动;副热带北太平洋和阿拉斯加湾的海表面温度(SST)变化呈偶极子振荡分布,这种准两年的周期振荡对这一模态的出现有一定的预示意义。而与气温变化的低纬模态相联系的大气环流表现为类AO正位相分布,与之相关的西伯利亚高压和阿留申低压南移,对流层中层东亚大槽东移,高层的西风急流则是向东南方向移动;赤道东太平洋的SST异常可能对这一模态的形成有一定的作用,而东亚近海的SST则更多是被动地改变。此外,海冰异常变化与东亚冬季气温变化的联系主要体现在:在前夏和前秋,东西伯利亚海-波弗特海海冰异常减少(增加)对应着随后东亚冬季气温变化的高纬模态(低纬模态),而冬季东亚气温变化的高纬模态(低纬模态)又与后期春季北极东半球的海冰异常增加(减少)具有较好的相关性,此外白令海和鄂霍次克海的海冰异常变化是伴随东亚冬季气温变化产生的。

The inter-annual component of winter mean（December to February of the next year） air temperature in East Asia（0°~60°N,100°E^140°E）,removing periods longer than eight years,is studied by using the empirical orthogonal function（EOF） analysis for the period 1979/1980~2009/2010.The winter mean surface air temperature variations are dominated by two distinct principal modes that together account for 73% of the total temperature variance.The first mode,named as the high-latitude mode,characterized by a westward shift of the East Asian major trough and enhanced surface pressure over central Siberia,is closely associated with the negative phase of Arctic Oscillation（AO） on the inter-annual time scale.The anomalous sea surface temperature（SST） between the subtropical North Pacific Ocean and the Gulf of Alaska represents a distribution of the dipole oscillation,and this quasi-biennial oscillation plays a significantly predictive role in the emergence of this mode.The second mode,named as the low-latitude mode,features an eastward shift of East Asian trough and increased surface pressure over Mongolia,is closely related to the positive phase of AO on the inter-annual time scale.The tropical Eastern Pacific La Nina-like SST anomalies are suggested to be contributive to produce this mode,while the SST along the coast of East Asia can only vary with the temperature passively.In addition,the East Asian winter mean temperature has a significant association with the anomalous sea ice concentration.When the light（heavy） sea ice prevails in East Siberian Sea and Beaufort Sea in the previous summer and autumn,the cold high-latitude（low-latitude） mode is simply significant in inter-annual scale,which will cause an anomalous increase（decrease） of the sea ice over the Eastern Hemispheric Arctic Sea,while the sea ice concentration over Bering Sea and Sea of Okhotsk will have a passively variation with respect to the temperature on the simultaneous winter.