J. Climate ,

Pacific-East Asian Teleconnection: How does ENSO affect East Asian Climate?


Renguang Wu, and Xiouhua Fu
Department of Meteorology, School of Ocean and Earth Science and Technology, University of Hawaii

Observational evidences are presented to show a teleconnection between the central Pacific and East Asia during the extreme phases of ENSO cycles. This Pacific-East Asian teleconnection is confined to the lower troposphere and characterized by a westward and poleward emanation of alternative cyclonic and anticyclonic vorticity anomalies from the equatorial central Pacific toward East Asia. The key system which connects the warm (cold) events in the eastern Pacific and the weak (strong) East Asian winter monsoons is an anomalous lower-tropospheric anticyclone (cyclone) located in the western North Pacific. The western North Pacific wind anomalies develop rapidly in late fall of the year when a warm or cold event matures. The anomalies persist until the following spring or early summer, causing anomalously wet (dry) conditions along the East Asian polar front stretching from southern China northeastward to east of Japan (Kuroshio extension). Using atmospheric general circulation and intermediate models, we show that the anomalous anticyclone over the Philippine Sea during mature phases of ENSO results from a Rossby wave response to suppressed convective heating due to the in situ ocean surface cooling and the descent forced remotely by the central Pacific warming. The persistence of the teleconnection is attributed to a positive thermodynamic feedback between the western Pacific anticyclone and the ocean mixed layer in the presence of the cold-season mean circulation. The rapid developments of the anticyclone and negative sea surface temperature anomalies suggest that the extratropical-tropical interaction through cold surge-induced exchange of surface buoyancy flux may play an important role.

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