Association between Tropical Convection and Boreal Wintertime Extratropical Circulation in 1982/83 and 1988/89
Association between Tropical Convection and Boreal Wintertime Extratropical Circulation in 1982／83 and 1988／89

Boreal wintertime extratropical circulation is studied in relation to the tropical convection during the1982/83 El Nino and 1988/89 La Nina. The anomaly structure of 1982/83 and 1988/89 over the extratropicsreveals remarkably different features as the longitudinal tropical forcing region changes. The Rossby wavesource (Positive) shows the largest maximum over East Asia in both years due to the persistent heating fromthe western Pacific warm pool area. However, the sink term shows contrasting features over the subtropicsand extratropics between the two years. In the El Nino year, enhanced tropical convection over the easternPacific produces the Rossby wave sink at 10°N and shifted eastward over the North Pacific, while in theLa Nina year, the sink area is shifted westward over the North Pacific. The contrasting features betweenthe two events in mean-eddy interaction appears especially over the downstream area of the East AsianJet. The extension (retraction) of the meanflow eastward (westward) to the east (west) of the datelineis related with the effect of the westward (eastward) E-vector and the strengthening (weakening) of thenegative anomalies of the barotropic growth of kinetic energy. Hence, almost opposite characteristicsbetween the two events can explain the close relationship of tropical convection and the extratropicalinternal variability.