【摘要】 运用NCEP/NCAR SLP再分析月资料,分析研究了北极涛动的季节性差异,着重讨论了夏季北极涛动的时空特征。结果表明,除了强弱的季节差异,夏季北极涛动与冬季北极涛动在空间模态上也存在较大差异,主要表现在夏季北极涛动的中纬度强活动中心从北大西洋地区转移到亚洲大陆上,其亚洲中心只在对流层低层比较明显,强度随高度增加而减小,因而在对流层中呈现出比冬季北极涛动更强的斜压性。这种模态在年际和月际时间尺度上均有所体现。夏季北极涛动在近50年来一直存在稳定的准22年周期,其次为6~7年周期。另外,从1970年左右开始出现准2年周期振荡,而1970年代以前准2年周期不明显。更多还原

【Abstract】 Using the NCEP/NCAR reanalysis monthly data of SLP,the seasonal difference of Arctic Oscillation(AO) is studied with the emphasis on the temporal and spatial features of the summer AO.The results indicate that the major discrepancy between the summer AO and winter AO lies on their mid-latitude active centers.The mid-latitude active center in winter AO locates at Atlantic ocean,it shifts over Asian continent in summer.The Asian center of the summer AO is significant only in the lower troposphere.In the upper troposphere,there is no Asian active center,which shows the summer AO stronger baroclinicity in contrast with the winter counterpart.This mode yields the similar spatial pattern,interannual and intermonth.In addition,the summer AO exhibits the strong quasi-22 and 6~7 year periods in the last 50 years,with the quasi-biannual period emerging after 1970′s.更多还原