摘要
A set of numerical experiments designed to analyze the oceanic forcing in spring show that the combined forcing of cold （warm） El Ni（n）o （La Ni（n）a） phases in the Ni（n）o4 region and sea surface temperature anomalies （SSTA） in the westerly drifts region would result in abnormally enhanced NorthEast Cold Vortex （NECV） activities in early summer.In spring,the central equatorial Pacific El Ni（n）o phase and westerly drift SSTA forcing would lead to the retreat of non-adiabatic waves,inducing elliptic low-frequency anomalies of tropical air flows.This would enhance the anomalous cyclone-anticyclonecyclone-anticyclone low-frequency wave train that propagates from the tropics to the extratropics and further to the mid-high latitudes,constituting a major physical mechanism that contributes to the early summer circulation anomalies in the subtropics and in the North Pacific mid-high latitudes.The central equatorial Pacific La Ni（n）a forcing in the spring would,on the one hand,induce teleconnection anomalies of high pressure from the Sea of Okhotsk to the Sea of Japan in early summer,and on the other hand indirectly trigger a positive low-frequency East Asia-Pacific teleconnection （EAP） wave train in the lower troposphere.
A set of numerical experiments designed to analyze the oceanic forcing in spring show that the combined forcing of cold （warm） El Ni（n）o （La Ni（n）a） phases in the Ni（n）o4 region and sea surface temperature anomalies （SSTA） in the westerly drifts region would result in abnormally enhanced NorthEast Cold Vortex （NECV） activities in early summer.In spring,the central equatorial Pacific El Ni（n）o phase and westerly drift SSTA forcing would lead to the retreat of non-adiabatic waves,inducing elliptic low-frequency anomalies of tropical air flows.This would enhance the anomalous cyclone-anticyclonecyclone-anticyclone low-frequency wave train that propagates from the tropics to the extratropics and further to the mid-high latitudes,constituting a major physical mechanism that contributes to the early summer circulation anomalies in the subtropics and in the North Pacific mid-high latitudes.The central equatorial Pacific La Ni（n）a forcing in the spring would,on the one hand,induce teleconnection anomalies of high pressure from the Sea of Okhotsk to the Sea of Japan in early summer,and on the other hand indirectly trigger a positive low-frequency East Asia-Pacific teleconnection （EAP） wave train in the lower troposphere.
基金
supported by a National Natural Science Foundation project approved under Grant Nos.41175083,41275096 and 41305091
a China Meteorological Administration special public welfare reserch funds registeredunder Grant Nos.GYHY201006020,GYHY 201106016,and GYHY201106015
