前冬北半球环状模对春季中国东部北方地区极端低温的影响  

Influences of the preceding winter Northern Hemisphere annular mode on the spring extreme low temperature events in the north of eastern China

作　　者：尹姗[1,2] 冯娟[1] 李建平[1] 

机构地区：[1]中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室,北京100029 [2]中国科学院大学,北京100049

出　　处：《气象学报》2013年第1期96-108,共13页Acta Meteorologica Sinica

基　　金：国家重点基础研究发展计划(973计划)项目(2010CB950400;2013CB430203);国家自然科学基金资助项目(41030961)

摘　　要：对1959—2008年前冬(12—3月)北半球环状模与春季(3—5月)中国东部北方地区极端低温事件的关系进行诊断分析,发现前冬北半球环状模与春季中国东部北方地区极端低温事件存在显著负相关。当前冬北半球环状模偏强时,春季中国东部北方地区上空对流层高、低层分别出现位势高度的负、正异常,对应异常的下沉增温,东北冷涡偏弱,极端低温事件发生频次偏少,强度偏弱;反之,当前冬北半球环状模偏弱时,春季该地区极端低温事件发生的频次偏多,强度偏强。进一步研究表明,欧亚雪盖在前冬北半球环状模对春季中国东部北方地区极端低温的影响中起到潜在的桥梁作用,当前冬北半球环状模偏强(偏弱)时,同期欧亚大陆中高纬度地区偏暖(偏冷),欧亚雪盖面积较小(较大)。另外,欧亚雪盖面积异常具有较强的持续性,可以从前冬持续到春季。因此,当前冬欧亚雪盖面积较小时,春季欧亚雪盖面积也偏小,且对应春季东北冷涡强度偏弱,中国东部北方地区地表气温偏高,极端低温事件发生的频次偏少,强度偏弱;反之亦然。前冬北半球环状模与春季中国东部北方地区极端低温事件的负相关关系为预测中国东部北方地区春季极端低温事件的变化提供了一个潜在的前期信号。The relationship between the preceding boreal winter Northern Hemisphere annular mode （NAM） and the spring extreme low temperature events in the north of eastern China during 1959 - 2008 was examined in this study. The results show that there exists a significantly negative relationship between the preceding winter （DecemberMarch） NAM and the following spring （MarchMay） extreme low temperature events in the north of eastern China. When the preceding winter NAM is strong, in the following spring negative （positive） geopotential height anomalies occur in the upper （lower） levels over the north of eastern China, and anomalous sinking motion and vertical heating are accompanied in the same area with the cold vortices over Northeast China being weak, resulting in less extreme low temperature events. The opposite circulation patterns in the spring are obviously observed in weak preceding winter NAM years. Furthermore, the possible physical mechanism associated with the impact of the preceding winter NAM on the subsequent spring extreme low temperature events in the north of eastern China is explored. The results indicate that the Eurasian snow cover is a potential bridge connecting the signals in winter NAM and spring extreme low temperature events in the north of eastern China. When the preceding winter NAM is strong （weak）, warmer （colder） surface air temperature occurs over the mid-high latitudes of Eurasia and the Eurasian snow cover area is smal- ler （larger） than normal. Besides, Eurasian snow cover area anomalies in the preceding winter can strongly persist to the fol- lowing spring. When the preceding winter Eurasian snow cover area is small, accordingly in the following spring cold vortices over Northeast China are weak and the surface air temperature in the north of eastern China is higher, resulting in less extreme low temperature events, and vice verse. Therefore, the preceding winter NAM contributes to the frequency and intensity of the following spring extreme low temperatu

关 键 词：北半球环状模 极端低温 负相关 欧亚雪盖 

分 类 号：P466[天文地球—大气科学及气象学]