[Meteorological Impact Assessment of PM 2.5 and O 3 Complex Pollution in Key Regions of China Based on Meteorological Conditions Index].

Meteorological conditions play a key role in the occurrence and evolution of atmospheric complex pollution. Considering the different pollution formation mechanisms of PM _2.5 and O ₃ , statistical calculation and in-depth learning methods were used to construct the PM _2.5 and O ₃ meteorological condition indexes based on long-term pollution meteorological observation data. A research method was developed to study the meteorological characteristics and impact contribution of atmospheric complex pollution by using the meteorological condition index, and quantitative analysis of the distribution and variation of pollution excluding the influence of regional meteorological differences was also conducted. The results showed that in the summer of 2021, the pollution meteorological conditions in the key regions in central and eastern China were generally worse in the north and better in the south(index:"2+26" cities>the border area of Jiangsu, Anhui, Shandong, and Henan>the Yangtze River Delta) and the worst in June and the best in July. The "double high" pollution began to appear when the PM _2.5 meteorological condition index>30 and O ₃ meteorological condition index>100; meanwhile, the unfavorable meteorological conditions for O ₃ also promoted the increase in PM _2.5 concentration, resulting in the frequency of "double high" increases with the increase in O ₃ meteorological condition index. Compared with that during the same period last year, ρ (PM _2.5 ) of each region decreased by 3.9 μg·m ^-3 , 3.3 μg·m ^-3 , and 1.4 μg·m ^-3 due to the contribution of the improvement in the pollution meteorological conditions, which is nearly 58.5% on average of the total decrease in PM _2.5 concentration. However, the change in O ₃ pollution meteorological conditions was better in the north and worse in the south, and the overall deterioration in the Yangtze River Delta Region led to approximately 2.8 μg·m ^-3 growth for the O ₃ concentration. The PM _2.5 and O ₃ concentrations after excluding the impact of meteorological differences showed different distribution characteristics from the air quality monitoring, in which the high concentrations of PM _2.5 were distributed along the Bohai Sea, the inter-provincial border, and the south of the region, whereas the high concentrations of O ₃ were concentrated along the Taihang Mountains, around Mount Tai, and in parts of the Yangtze River Delta. The daily concentration variations in a single city during a specific pollution control period could be used as a basis for evaluating the effectiveness of local supervision and control, which will provide a reference for the dynamic supervision and daily scheduling of local control management.