地面以下虚假经向风场对非洲地区局地Hadley环流的影响

Influence of fake below-ground meridional wind on regional Hadley circulation in Africa

利用热带地区垂直翻转环流分解方法(简称"M1")和全球大气环流三型分解方法(简称"M2"),采用7套再分析资料,分析地面以下虚假经向风场(fake below-ground meridional wind,FBGMW)对非洲大陆地区Hadley环流(Hadley circulation in Africa,AFHC)气候态、年际变率和线性趋势的影响。结果表明:(1)对于气候态而言,FBGMW对AFHC强度、AFHC公共上升支和南北半球下沉支的影响取决于季节和质量流函数计算方法的选取。(2)除了AFHC公共上升支,FBGMW对南北半球AFHC强度、AFHC下沉支位置年际变率的影响很小。不考虑FBGMW会使得M1方法对应的冬季和夏季以及M2方法对应的冬季AFHC公共上升支年际变率减小,M1和M2方法对应的秋季AFHC公共上升支年际变率增加。不考虑FBGMW导致M1方法对应的春季和M2方法对应的春季和夏季AFHC公共上升支年际变率的变化依赖于资料的选取。(3)尽管不考虑FBGMW会导致AFHC强度以及AFHC公共上升支和南北半球下沉支位置线性趋势的数值发生变化,但关于AFHC线性趋势的主要结论未改变。

The impacts of fake below-ground meridional wind(FBGMW)on the regional Hadley circulation in Africa(AFHC)in terms of the climatology,interannual variability,and linear trends have been analyzed based on seven reanalysis datasets by using the local partitioning method of the tropical overturning circulation(M1)and the three-pattern decomposition of global atmospheric circulation(M2).The results are as follows:(1)In terms of the climatology,the impacts of FBGMW on the intensity,common rising branch,and sinking branches in both hemispheres of the AFHC depended on the seasons and methods for the calculation of mas stream function.(2)Except for the common rising branch,the FBGMW had small impact on the interannual variability of the intensity of AFHC and the sinking branches location of AFHC in both hemispheres.No-considering FBGMW led to smaller interannual variability of the common rising branch of AFHC in winter and summer based on M1 method and in winter based on M2 Method,and larger interannual variability of the common rising branch of AFHC in autumn based on both methods.With no-considering FBGMW,the change of the interannual variability of the common rising branch of AFHC in spring based on M1 method and in spring and summer based on M2 method depended on the choice of the reanalysis data.(3)Although no-considering FBGMW,it had impact on the quantitative values of the linear trends of the intensity,common rising branch,and sinking branches location in both hemispheres of AFHC,the main conclusions of these linear trends did not change.