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
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
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
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
the extratropical-tropical interaction through cold surge-induced exchange of surface buoyancy
may play an important role.
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