1990年代和2000年代华北寒潮的对比及其与北极海冰的联系

Comparison of Cold Surges across North China between the 1990s and the 2000s and Their Relationships with Arctic Sea Ice

基于华北区域均一化站点气温资料、NCEP/NCAR大气再分析资料、CFSR大气再分析资料以及NOAA高分辨率北极海冰密集度资料,对比研究了1990年代与2000年代华北寒潮的差异及其与秋、冬季北极海冰的联系。结果表明:影响华北的区域性寒潮事件在1990年代(2000年代)发生的频次为1957~2011年最多(少),但寒潮平均强度偏弱(强),冷空气大多源自格陵兰岛(新地岛)附近,取偏西(偏北)路径进入华北。秋、冬季新地岛附近以及巴芬湾附近海冰在2000年代初显著减少,导致1990年代与2000年代出现显著环流差异:1990年代(2000年代)极区位势高度存在负异常(正异常),欧亚大陆大型槽脊波动较弱(强),绕极区西风较强(弱),东亚大槽较弱(强),西伯利亚高压较弱(强),使得华北寒潮在两段时间出现上述差异。

The present study compares North China's cold surges in the 1990s and 2000s and their relationships with Arctic sea ice using the observed temperature,two atmospheric reanalyses from NCEP/NCAR,and a set of highresolution sea ice concentration data from NOAA.In the 1990s,North China experienced less frequent cold surges with a strong relative intensity from 1951 to 2011,resulting from cold air originating from Greenland and invading North China and the western path.Contrary,cold surges in the 2000s occurred most frequently with a weak relative intensity during 1951−2011;the cold air originating from Novaya Zemlya invaded North China along northern path.Since the early 2000s,the sea ice in Novaya Zemlya and Buffin Bay has experienced a significant decrease in autumn and winter,which changed some atmospheric circulation systems.The Eurasian continent experienced a stronger large-scale trough/ridge with a stronger East Asia trough and Siberian High.In addition,weaker westerlies and higher geopotential height were observed around the Arctic in the 2000s compared to those in the 1990s,leading to the difference in cold surges in North China between these two decades.