Hadley环流的双层结构及其年代际演变特征

THE DOUBLE-LAYER STRUCTURE OF HADLEY CIRCULATION AND ITS INTERDECADAL EVOLUTION CHARACTERISTICS

利用1948—2011年NCEP/NCAR月平均水平风场资料,采用全球大气环流的三型分解等方法,研究了Hadley环流的双层结构及其年代际演变特征。结果表明：（1）Hadley环流双层结构客观存在,且4、5、6、10、11月南半球Hadley环流双层结构长期存在;（2）南半球Hadley环流双层结构较北半球更加明显,双层结构在垂直方向上呈现倾斜状,对Hadley环流强度和中心位置的变化进行研究时,应考虑双层结构的影响;（3）4、5、6、10、11月南半球Hadley环流强度随时间都呈现强弱强的年代际演变特征,各个月份环流强度都存在20-30年和40-60年时间尺度的周期;（4）4、5、6、10、11月南半球环流中心位置（双层结构平均位置）随时间一致地表现为向南移动,各个月份环流中心分别向南移动了5.18°、2.11°、2.50°、1.79°、5.76°,平均向南移动了3.47°。

Based on a three-pattern decomposition model of the large-scale atmospheric circulation, this paper studies the double-layer structure of the Hadley circulation and its interdecadal evolution characteristics by use of monthly horizontal wind data from NCEP/NCAR reanalysis during 1948-2011 and obtains the following major conclusions. Firstly, the double-layer structure of the Hadley circulation is an objective fact and it constantly exists in April, May, June, October and November in the Southern Hemisphere （SH）. Secondly, the double-layer structure is more obvious in the SH than the Northern Hemisphere. It is sloped in the vertical direction. The double-layer structure should be taken into account when analyzing the variability of the strength and the center of the Hadley circulation. Thirdly, the strength of the double-layer structure of the Hadley circulation in the SH consistently exhibits decadal variations with a strong-, weak- and then-strong-again- pattern in all of the five months with a cycle of 20 - 30a and 40 - 60a. Fourthly, its center （ mean position of the double-layer structure） in the SH consistently and remarkably shifts southward in all the five months. The net poleward shift over the 64 years is 5. 18 °, 2. 11 °, 2. 50 °, 1.79 ° and 5.76 o for the five months, respectively, with a mean shift of 3.47 °.