Has the regional Hadley circulation over western Pacific during boreal winter been strengthening in recent decades?

Abstract

Previous studies suggest a robust intensification of the zonally averaged hadley circulation (HC) during boreal winter in recent decades, but little is known regarding the regional HC. This study investigates long-term trends of the winter regional HC over the western pacific (WPHC) since 1979 using six reanalysis datasets. It is found that there are large discrepancies in the long-term trends of WPHC intensity among the six datasets. Specifically, three of the six reanalyses (era-interim, 20CR and CFSR) show no discernible long-term trends, whereas NCEP-1, NCEP-2 and JRA-55 display pronounced intensification tendencies. Results in this study suggest that, although the warming trend of SST in the western tropical pacific identified in previous studies is robust, uncertainty remains regarding the long-term trends in the WPHC intensity. This raises a question about the factors involved in changes of the WPHC intensity.