亚洲季风区内北半球秋季哈德莱环流特征及其与热带海温之间关系

Characteries of Boreal Autumn Hadley Circulation over the Asian Domain and Its Relationship with Tropical SST

利用1979-2020年英国气象局哈德莱中心海冰和海表面温度数据集以及NCEP再分析资料,分析了北半球秋季亚洲季风区内哈德莱环流(Hadley Circulation,HC)特征及其与热带海温之间的关系。结果表明:近42年秋季区域HC表现为非赤道对称,上升支位于赤道附近,下沉支位于副热带地区。区域HC的第一模态(EOF1)占比59%,空间分布表现为非赤道对称,北部分支为主体且大于南部分支,上升支位于赤道以南;时间系数主要表现为年际变化,且与ENSO(El Nino-Southern Oscillation)事件有关。在拉尼娜(La Nina)事件发生期间,由于热带印度洋(Tropical Indian Ocean,TIO)的海温表现为显著的负异常且北半球TIO的异常降温大于南半球TIO,进而导致TIO出现异常的经向梯度从而促进EOF1模态的形成。第二模态(EOF2)占比15%,其空间分布表现为南部分支范围与区域HC上升支范围一致,时间分布表现为增长的趋势,而上升支的范围与亚洲季风区TIO南北两个半球海温的增暖趋势相关,由于北半球TIO的增温速率快于南半球TIO,从而导致区域HC上升支的范围偏北。

Using the Hadley Centre Sea Ice and Sea Surface Temperature dataset and NCEP reanalysis data during 1979-2020,this paper analyzes the characteries of boreal autumn Hadley circulation(HC)over the Asian domain and its relationship with tropical sea surface temperature.The results find that the autumn regional HC is equatorial asymmetric in the last 42 years,with ascending branch located near the equator and sinking branch in the subtropical.The first model(EOF1)accounts for 59%,and the spatial distribution of the autumn regional HC is equatorial asymmetric,with the northern cell is dominant and larger than the southern cell.The ascending branch located to the south of the equator,The time distribution shows an interannual variation and it’s related to the ENSO(El Nino-Southern Oscillation).During the La Nina events,the Tropical Indian Ocean(TIO)exists the significant negative anomaly and the abnormal cooling in the northern Indian Ocean is greater than that in the southern Indian Ocean,which leads to the anomalous meridional gradient in the TIO.It promotes the formation of EOF1.The EOF2 accounts for 15%,and the spatial distribution in the EOF2 shows that the southern cell is consistent with the region HC ascending branch range.The temporal distribution shows an increasing trend.The range of the rising branch is related to the warming trend of the TIO southern and northern hemispheres in the Asian monsoon region.The warming rate of the northern TIO is faster than the southern TIO,resulting in regional HC ascending scope of the north.