Numerical experiments on the impact of spring north pacific SSTA on NPO and unusually cool summers in Northeast China |
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Authors: | LIAN Yi ZHAO Bin SHEN Baizhu LI Shangfeng LIU Gang |
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Institution: | 1. Laboratory of Research for Middle-High Latitude Circulation Systems and East Asian Monsoon, Changchun 130062 ;Institute of Meteorological Sciences of Jilin Province, Changchun 130062 2. National Meteorological Center,Beijing,100081 3. Laboratory of Research for Middle-High Latitude Circulation Systems and East Asian Monsoon, Changchun 130062 ;Jilin Meteorological Science and Technology Service Center, Changchun 130062 |
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Abstract: | A set of numerical experiments designed to analyze the oceanic forcing in spring show that the combined forcing of cold (warm) El Niño (La Niña) phases in the Niño4 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 Niño 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-anticyclone-cyclone-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 Niña 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. |
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Keywords: | atmospheric model westerly drifts Ni(n)o4 SSTA low-frequency variation circulation pattern cool summer Northeast China |
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