Meteorological mechanism of regional PM2.5 transport building a receptor region for heavy air pollution over Central China

Regional transport of air pollutants is a key factor affecting air quality over the receptor region, where the meteorological mechanism of regional transport influence has not been fully understood. The Twain-Hu Basin (THB) in central China is located in the downwind area of major pollutant sources over central and eastern China (CEC) under the East Asian winter monsoonal winds. To understand the meteorological mechanism of regional PM2.5 transport building a receptor region for heavy air pollution, an ensemble of 8 typical heavy air pollution events with regional PM2.5 transport in January of 2015-2019 were selected objectively by using the MV-EOF (multivariable empirical orthogonal function) decomposition with multi-source observations, and the meteorological configurations driving the regional PM2.5 transport and building a receptor in the THB with heavy air pollution were investigated. The results showed that PM2.5 from the source area in northern China to the THB was actuated by cold air southward invasion with strong northerly winds in the lower troposphere, and the vertical structure of atmospheric circulation was characterized with the typical pattern of southward advance of cold front with the cold air confronting the warm air mass over the THB area. The warm air mass and the windward side of THB's basin terrain formed a "barrier" in regional transport of PM2.5 over central China, which were conducive to accumulating PM2.5 for heavy air pollution in the THB. Furthermore, an abnormal warm air layer in the middle troposphere acted as the upper "warm lid", suppressing the vertical PM2.5 diffusion over the receptor region. With such the 3-D atmospheric structure, a key receptor region in the THB for heavy air pollution was built in regional PM2.5 transport over China. These findings could enrich the scientific understanding of the meteorological mechanism on air pollution with regional transport of source-receptor air pollutants in atmospheric environment change.