Climatological changes in East Asian winter monsoon circulation in a warmer future

Abstract

The assessment of future climate changes can be challenging if the anthropogenic influence on these changes cannot be determined. Understanding anthropogenic effects on climate variability may improve decadal predictability. In the present study, we investigated the changes in the climatology of the East Asian winter monsoon circulation and evaluated the extent to which these changes are regulated by global warming. We focused on the interannual fluctuation in the upper-level westerly jet stream and its connection with the underlying monsoon circulation, including the strength of the midlevel coastal trough and the zonal contrast in surface pressure. Evaluation of climatological changes in the relationships among various circulation patterns, particularly in the context of present and future decades of global warming, may help scholars differentiate between natural and anthropogenic effects on monsoon dynamics. Reduced interannual fluctuation in the jet stream was noted over the last half century, as was considerably increased global surface temperature. Thus, the monsoon related vertical circulation patterns will tend to become disconnected from each other. In a warmer future, global warming induced suppression of the jet stream's interannual fluctuation and its detachment from the low-level monsoon circulation may be common, and these events may be perturbed by climate oscillations.