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

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(erainterim,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.

北半球冬季西太平洋哈德莱环流是否在增强?先前的研究表明冬季全球纬向平均的哈德莱环流存在显著增强的趋势,但是局地哈德莱环流强度的长期趋势还不清楚。本文使用六套再分析数据探讨了冬季西太平洋哈德莱环流强度的长期趋势。结果表明冬季西太平洋哈德莱环流强度的长期趋势在六套不同的再分析资料中存在很大的差异。其中有三套资料(ERA-Interim、20CR和CFSR)表明其没有增强的趋势,而另三套资料(NCEP-1、 NCEP-2和JRA-55)却表明其具有显著的增强趋势。前人的研究已经表明热带西太平洋海温增暖显著,但是本文的研究结果表明西太平洋哈德莱环流强度的趋势还存在不确定性。因此,本文的研究促使我们进一步思考影响西太平洋哈德莱环流强度变化的真正因子。