北太平洋Hadley环流纬向结构的季节和年际变化

Seasonal and interannual variability of the zonal structure of Hadley Circulation over the northern Pacific Ocean

为了描述北太平洋上空Hadley环流的纬向结构特征,利用NCEP再分析资料(1979~2010年),研究了北太平洋上空Hadley环流纬向结构的季节和年际变化。发现在西太平洋,Hadley环流季节性上升支呈西北-东南倾斜,其垂向核心位于对流层中层,纬向核心在北半球冬季(夏季)位于日界线附近(150°E);而永久性上升支主要在东太平洋,其垂向核心位于对流层低层,且沿经度东移逐渐增强。根据纬向环流结构特征,北半球冬季环流形态分为3个区域:160°E以西,主要表现为低层辐合高层辐散;160°E^130°W,主要表现为高层辐合;130°W以东,表现为低层辐合高层辐散特征。相似地,北半球夏季环流形态也可沿纬向分为如下3个区域:165°E以西、165°E^165°W和165°W以东,分别对应东亚夏季风主导经圈环流区、过渡区、Hadley环流主导经圈环流区。在年际变化上,北太平洋Hadley环流与ENSO有很强的相关,这与前人的研究是一致的。因此北太平洋上空Hadley环流具有显著的空间性态,并且对应时间尺度不同,影响其变化的主要因素也不尽相同。

The seasonal and interannual variability of zonal structure of Hadley circulation over the northern Pacific Ocean was examined with the reanalysis data during the period of 1979 -2010 from NCEP/NCAR. The seasonal upward flow shows a slope from northwest to southeast in the western Pacific Ocean, whose vertical maximum is located near the middle of the troposphere and zonal maximum at about 180°E （150°E） in boreal winter （summer）;while the permanent upward flow is mainly distributed over the eastern Pacific Ocean, whose vertical maximum lies in the lowest layer of troposphere, with a zonal structure enhancing from west to east. The pattern of the circulation in boreal winter could be divided into three areas based on the zonal structure. The area to the west of 160°E exhib-its convergent in the lower layer and divergent in the higher layer; the area between 160°E-130°W exhibits con-vergent in the higher layer;the area to the east of 130°W exhibits convergent in the lower layer and divergent in the higher layer. Similarly, the pattern in boreal summer could also be divided into three areas as follows. The area to the west of 165°E is East Asia Summer Monsoon （EASM）-dominated area, the area of 165°E-165°W is a transition zone, the area to the east of 165°W is dominated by Hadley circulation. The analysis of relationship between Hadley circulation and ENSO shows a strong correlation, which is consistent with previous reports.