从2011/2012和2015/2016年冬季大气环流异常看北极海冰以及前期夏季北极大气环流异常的作用

Roles of Arctic sea ice and the preceding summer Arctic atmospheric circulation anomalies in the atmospheric circulations anomalies of 2011/2012 and 2015/2016 winters

中文关键词:  北极海冰  西伯利亚高压  北冰洋  反气旋  厄尔尼诺事件

英文关键词:Arctic sea ice  Siberian high  Arctic Ocean  Anticyclone  El Niño event

中文摘要:

      利用美国NCEP/NCAR、欧洲中心ERA-Interim再分析资料，以及英国哈得来中心海冰密集度资料，通过诊断分析和数值模拟试验，研究了2011/2012和2015/2016年两个冬季大气环流异常的主要特征和可能原因。结果表明，尽管热带太平洋海温背景截然不同（分别为弱的拉尼娜事件和强厄尔尼诺事件），但这两个冬季西伯利亚高压均异常偏强，自1979年以来其强度分别排第1和第5位。前期秋季北极海冰异常偏少是导致这两个冬季西伯利亚高压偏强的主要原因。更为重要的是，前期夏季北冰洋表面反气旋风场，以及其上空对流层中、低层平均气温偏高，加强了北极海冰偏少对冬季大气变率的负反馈，进一步促进了西伯利亚高压的加强，从而有利于东亚地区冬季阶段性强严寒的出现。因此，夏季北极大气环流的动力和热力状态不仅影响夏、秋季北极海冰，而且对海冰偏少影响亚洲冬季气候变率有重要调节作用。2015/2016年冬季强厄尔尼诺事件并不能掩盖来自北极海冰和大气环流的影响。

英文摘要:

      Using the NCEP/NCAR re-analysis data (re-analysis I), the ERA-Interim re-analysis data, and Hadley Center Arctic sea ice concentration data, main characteristics of atmospheric circulation anomalies in the winters of 2011/2012 and 2015/2016 were investigated based on diagnostic analysis and numerical simulations, and the possible causes were revealed. The results indicate that although sea surface temperature anomalies in the tropical Pacific in the two winters corresponded to a weak La Nia and a strong El Nio event respectively and were distinctly different, the Siberian high was very strong in both winters, ranking the highest and the 5th highest since 1979, respectively. Autumn Arctic sea ice loss is a major reason that causes strong Siberian high in both winters. More important, anticyclonic surface winds in the preceding summer season over the Arctic Ocean and higher than normal air temperatures in the mid- and low-troposphere aloft strengthen the negative feedback of Arctic sea ice loss on the winter atmospheric variability, which further enhances the Siberian high and thereby favors the occurrence of extreme cold events in East Asia. Apparently the dynamic and thermal dynamic conditions of summer Arctic atmospheric circulation not only influence Arctic sea ice in the summer and autumn, but also modulate the effects of Arctic sea ice loss on winter atmospheric variability. The strong El Niño event in the winter of 2015/2016 couldn't offset effects of Arctic sea ice loss and atmospheric circulation anomalies on the winter atmospheric variability over East Asia.