冬季Hadley环流与热带海表面温度的关系及其对中国气候的影响

Relationship between the Hadley circulation and tropical sea surface temperature in winter and its impact on China's climate

利用1979-2021年全球海表面温度(SST)、气象再分析资料等数据,探讨冬季Hadley环流(HC)的变率及其与热带SST异常的关系,研究其对中国同期降水量和气温的影响.结果表明,HC的EOF_(1)模态(46.2%)是上升支在10°S左右的主体位于北半球的非对称模态,包含年代际和年际变率.年代际变率与印度洋(20°S~20°N,50°~90°E)SST南北不均匀增暖趋势有关(南半球大于北半球);年际变率与El Ni?o事件下印度洋(10°S~10°N,50°~90°E)异常SST经向梯度沿正方向为0的位置出现在南半球有关.EOF_(2)模态(16.7%)是关于赤道对称模态,仅体现年际变率,与El Ni?o事件下热带东太平洋(180°E~90°W)异常对称的经向热力结构有关.两个主模态与中国同期降水量和气温均呈正相关.在EOF_(1)(EOF_(2))模态影响下,中国东南沿海地区(南方地区东南部)降水偏多,与110°~120°E异常反环流有关.EOF_(1)模态下,中国西北-中部地区存在气温正距平,与下沉运动的绝热加热效应关系密切.EOF_(2)模态下,中国气温也为正距平,但温度异常不显著.

Using the global sea surface temperature(SST)data and reanalysis data from 1979 to 2021,the variability of the boreal winter Hadley circulation(HC)and its relationship with tropical SST anomalies were discussed,and its impact on contemporaneous precipitation and temperature in China further studied.The results indicated that the EOF_(1)mode of HC(46.2%)was an asymmetric mode with the main body of the ascending branch located around 10°S in the northern hemisphere,including interdecadal and interannual variability,the former being closely related to the Indian Ocean(20°S-20°N,50°-90°E)SST with the non-uniform north-south warming trend(more in the southern hemisphere than in the northern hemisphere);interannual variability was related to the Indian Ocean(10°S-10°N,50°-90°E)where the anomalous SST meridional gradient along the positive direction(and the gradient changing from positive to negative)being zero occurred in the southern hemisphere under the El Niño event.The EOF_(2)mode(16.7%)was about the equatorial symmetric mode and only reflected the interannual variability.This mode was associated with the anomalous symmetric meridional thermodynamic structure of the tropical eastern Pacific(180°E-90°W)under the El Niño event.The two modes were roughly positively correlated with contemporaneous precipitation and temperature in China.Under the influence of EOF_(1)(EOF_(2))mode,there was more precipitation in the southeastern coastal areas of China(southeast of the southern region),relating to the ascending branch of HC in the region of 110°-120°E.In the EOF_(1)mode,there was a positive temperature anomaly in the northwest-central region of China,which was closely related to the adiabatic heating effect of the subsidence movement.Under the EOF_(2)mode,the temperature in China was also a positive anomaly,but the temperature anomaly was not significant.