THE EVOLUTION CHARACTERISTICS OF HADLEY CIRCULATION ASCENDING BRANCH AND ITS RELATION TO THE VARIATION OF LOW-LATITUDE ATMOSPHERIC OZONE

LI Qiong; GUO Shi-chang; LI Zu-xian; TANG Lin; WANG Ling; DING Li

doi:10.16032/j.issn.1004-4965.2018.03.015

Abstract：Based on the NCEP/NCAR monthly mean wind data and ECMWF monthly mean multi-layered ozone mass mixing ratio data and by defining the Hadley circulation ascending branch intensity index (HAI), we studied the evolution characteristics of HAI and its relation to the variation of low-latitude atmospheric ozone in different levels with the mass stream function method. The results showed that ① HAI is bigger in summer and winter and smaller in spring and autumn with the maximum in February and August and the minimum in May and November. The position of Hadley circulation ascending branch changes with the season and strength;The latitude span of Hadley circulation ascending branch is the widest in winter and narrowest in summer. ② The HAI has inter-decadal characteristics in different months representing the four seasons. Namely, HAI has a negative-stalemate-positive anomaly inter-decadal characteristics in January and April and it performs in a linearly positive trend. While HAI presents a positive-negative-positive anomaly changes in July and October, it is weakened obviously in July. As a whole,the significantly strengthened tendency starts from the late 1990s. ③ Besides the spring, Hadley circulation ascending branch performs remarkable transporting function in the low-latitude tropospheric ozone. The tropospheric ozone concentration on the corresponding latitudes of Hadley circulation rising branch is reducing with the strengthening of Hadley circulation ascending branch while the tropospheric ozone concentration on the two subsidence zones of Hadley circulation is increasing. ④ When the annual mean HAI showed a strong index, the low latitude tropospheric ozone performance increases and the lower stratospheric ozone reduces, which reflects the long-term comprehensive influence of Hadley circulation and the atmospheric ozone at each level.