Abstract:
Using Ozone Monitoring Instrument (OMI) data and NCEP meteorological data aboard the US Environmental Monitoring Aura satellite from January 2005 to December 2017, the winter circulation index in South Asia is redefined based on the definition of the summer monsoon index, and the South Asian summer monsoon and winter wind circulation index are calculated respectively. The temporal and spatial variation characteristics of ozone under abnormal circulation in winter and summer are discussed by using correlation analysis, composite analysis and Singular Value Decomposition (SVD). The results show that: ① In South Asia, the intensity of zonal circulation is consistent with that of meridional circulation in summer, but the intensities of the two types of circulations are very different in winter. ② In the past 13 years, the distribution of total ozone in South Asia has undergone obvious seasonal changes, and the total amount of ozone has shown an upward trend. ③ Circulation index in summer monsoon (winter monsoon) has a significant correlation with ozone in the middle and lower (the middle and high) troposphere and also with ozone in the middle and lower (the middle and high) stratosphere, but in winter the correlation in the stratosphere and the troposphere demonstrates an opposite trend. ④ The enhancement of summer monsoon circulation corresponds to the enhancement of upward airflow movement over the Qinghai-Tibet Plateau and the southern part of the Iranian Plateau, and the transport of ozone leads to the difference of tropospheric ozone distributions. ⑤ During the strong and weak winter circulation periods, the vertical movement of updraft center and downdraft center, and the difference between the north-south airflow and the east-west airflow are the causes of the different distributions of ozone. This further proves that the definition of the winter circulation index is reliable.