Monsoon circulation in relationship to spatiotemporal aerosol distribution over East Asian region

Abstract

Aerosols are important air pollutants that affect human health directly but also an important climate forcing agents. East Asia is considered one of the rapid economic development regions, also the most prevalent circulation of the monsoon cycle with a large amount of aerosol sources. And aerosols variability in the atmosphere is highly influenced by weather conditions both in space and time scales. In this study, the variation of aerosol distribution has been investigated following to relationship with certain monsoon conditions to unravel the potential impacts of weather changes on aerosol loading in spring and summer as well. Seventeen years record of Aerosol Optical Depth (AOD) data in collection 6, level 3 derived from Moderate Resolution Imaging Spectroradiometer (MODIS) were mainly employed to demonstrate the aerosol variation over the East Asia region. The monsoon index has been built based on the geopotential height to examine the relationship between Asian monsoon and aerosol variability. Two smaller regions as Northern region (108-130E; 30-40N) covering Northeast China and the Yellow Sea; Southern region (104-122E; 20-30N) covering Southeast China that represents two regions with different aerosol distribution pattern in East Asia have been divided based on the AOD index. Additions two groups of contrasting years standing for weak and strong monsoon has been picked based on the monsoon index to explore how aerosol variability would change in relationship with monsoon circulation. First, aerosol distribution has great seasonal variation over East Asia. The highest AOD value observed in East Asia in pre-monsoon (spring) and monsoon (summer) have experienced higher aerosol loading relative to the rest of the season in fall and winter. The aerosol concentration tends to change from cold months with a low value to warmer months with a higher value. The maximum aerosol loading has been found in the summer season over Northeast China and a lower value in Southeast China. Second, in terms of the inter-annual variation characteristics of aerosols, aerosol concentration has been raised as of 2000 and touch the highest value in 2011 on the North sub-region in summer, and a gradual decrease was found on the period after. The strong fluctuation in aerosol loading mainly was found in the summer season whereas no significant variability was detected in the springtime. Besides, the result also showed that aerosol loading has an un-notable difference in both Northern and Southern regions during springtime, but in the summer season, the aerosol tends to the Northward under favorable atmospheric conditions leading to be accumulated on the Northern region relative to the Southern side. These results improve our comprehension of an overall picture of the relationship between the atmospheric aerosol and meteorological variables under monsoon conditions.