Has the East Asian Westerly Jet Experienced a Poleward Displacement in Recent Decades?

Previous studies have suggested a poleward shift of the zonally averaged jet stream due to rapid warming over continents. However, the regional characteristics of the change in the jet stream are not yet understood. Here, we present evidence suggesting that the East Asian westerly jet did not shift poleward in past decades (1980--2004 relative to 1958--1979), both in winter and summer. Rather, the jet axis has moved southward in summer, but its meridional position is steady in winter. The main change of the jet stream in winter is the enhancement of its intensity. These changes in both summer and winter are consistent with the corresponding changes in the large meridional tropospheric temperature-gradient zone. Based on these results, we suggest that the changes of the jet stream over East Asia are unique and are different from the zonal mean jet stream over the Northern Hemisphere and over the North Atlantic region.