摘要:基于1979~2015年ERA-Interim再分析资料，分析了夏季亚洲高空急流纬向非对称变异特征及其可能的外强迫因子。研究发现夏季亚洲200 hPa纬向风异常EOF第二模态（方差贡献为16.4%）主要表现出了急流纬向非对称的空间异常形态，反映了西亚和东亚区域急流南北偏移的反位相变化。通过进一步的诊断分析，我们发现急流纬向非对称变异与北大西洋海表温度（简称海温）和欧亚陆面热力异常可能存在一定的联系。北大西洋三极型海温异常会激发出向下游传播的异常波列，夏季该波列在欧亚大陆上空的异常环流中心与急流纬向非对称相关的异常环流中心对应一致，其中东欧平原的异常反气旋和巴尔喀什湖附近的异常气旋对西亚急流变化存在影响，东亚地区急流的变化与贝加尔湖北部异常气旋和贝加尔湖南部的异常反气旋有关。对比欧亚土壤湿度关键区内垂直环流，陆面热力异常可能会改变局地环流进而影响急流变异，且这种影响存在区域差异。
关键词:夏季亚洲高空急流/
纬向非对称变异/
北大西洋海温三极子/
欧亚陆面热力异常
Abstract:Based on the ERA-Interim reanalysis data during 1979-2015, the zonally-asymmetric variation of summer Asian upper-tropospheric jet and its possible external forcing factors are analyzed. The second empirical orthogonal function mode of summer Asian 200-hPa zonal wind anomalies, which accounts for 16.4% of total variance, is characterized by zonally asymmetric spatial distribution. This mode reflects the out-of-phase changes of meridional displacement of jet over West Asia and East Asia. The North Atlantic sea surface temperature anomalies (SSTA) and the Eurasian surface thermal anomalies may have a linkage with the zonally asymmetric variation. The tripole pattern of North Atlantic SSTA in the spring can trigger anomalous wave trains that propagate downstream with anomalous circulation centers over Eurasian in the summer corresponding to circulation anomaly centers associated with the zonally-asymmetric variation of the Asian jet. The anomalous anticyclonic circulation around the East European Plain and anomalous cyclonic circulation around Lake Balkhash associated with the wave trains can affect the West Asian jet. In addition, the East Asian jet is well correlated with the anomalous cyclonic circulation to the north of Lake Baikal and the anomalous anticyclonic circulation to the south. Land surface thermal anomaly may also lead to changes in local circulation and affect the jet variation by modulating vertical motion and land-atmosphere interaction over soil moisture key areas and the impacts are regionally different.
Key words:Summer Asian upper-tropospheric Jet/
Zonally asymmetric variation/
North Atlantic SST anomaly tripole/
Eurasian land surface thermal anomaly
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