1960—2013年渤海海冰大气环流异常特征

Characteristics of anomalous atmospheric circulation for sea ice in Bohai Sea from 1960 to 2013

利用1960—2013年渤海冰情等级资料和500 h Pa的NCEP高度场再分析格点资料,采用合成分析、相关分析和t检验等方法,分析渤海海冰等级的年际变化特征,探讨了渤海海冰重冰年和轻冰年的大气环流特征,寻找引起海冰异常的500 h Pa环流关键区。结果表明:1960—2013年渤海冰情等级有明显的阶段性变化,其中20世纪60年代渤海海冰重冰年较多,80—90年代海冰重冰年较少,近几年渤海重冰年呈增多的趋势。海冰重冰年冬季北半球500 h Pa环流有明显的异常特征,主要表现在极涡偏向东半球,极涡中心强度明显偏弱且极涡面积明显偏小,东亚大槽强度偏强,欧亚脊线位于乌拉尔山一带,明显偏西;而轻冰年与常冰年类似,异常特征不明显。渤海海冰等级与西太平洋副热带高压的面积、强度和北界有较好的负相关关系;在500 h Pa高度距平场上,冬季欧亚地区重冰年为明显的南北向"-+"距平分布,轻冰年呈南北向"+-"距平分布,环流型差异在1月最明显;500 h Pa月高度场与渤海冰情等级存在5个较好相关区,其中蒙古上空的相关区最好,相关系数最大值达-0.71。

Based on sea ice level data in the Bohai Sea and the NCEP/NCAR reanalysis grid data of 500 hPa geo- potential height from 1960 to 2013, characteristics of interannual sea ice levels and atmospheric circulation in a year with heavy and light sea ice were analyzed by methods of a composition analysis, a correlation analysis and a T- test,in order to find a key area of 500 hPa circulation causing sea ice anomaly. The results indicate that sea ice lev- els in the Bohai Sea have a significant stage change. For example,most heavy sea ice occurs in 1960s and seldom during 1980s to 1990s;the number of years with heavy sea ice is in an increasing trend in recent years. 500 hPa winter atmospheric circulation in the north hemisphere has significant anomaly in the years with heavy sea ice, and it shows that polar vortex in the north hemisphere biases the eastern hemisphere; the strength of polar vortex center is weak and areas of polar vortex becomes significantly small; East Asia trough is stronger and Eurasian ridge is bi- ased west, located in the Eurasian area. However, anomaly characteristics are not significant in the years with light sea ice and in the normal years. The sea ice levels in the Bohai Sea are negative correlations with areas and strength of the Western Pacific subtropical high （WPSH） as well as its north side boundary. In the years with heavy sea ice ,500 hPa height anomaly field shows the distribution of ＂ - ＋＂ from north to south over Eurasian re- gion in winter, while it is opposite in the years with light sea ice and their differences are the most significant in January. Correlations between 500 hPa monthly average height field and sea ice levels in the Bohai Sea are better in five areas ,especially over the Mongolia with the maximum correlation coefficient （ -0.71 ）.