Spatial Variation of Surface Ozone Concentration During the Warm Season and Its Meteorological Driving Factors in China

Abstract

The concentration of surface ozone (O3) in China increased consistently from 2015 to 2018, and became an important air pollutant, followed by particulate matter. This study uses real-time O3 and meteorological data, obtained in 337 cities in China during the warm seasons (April to September) of 2015 to 2018, to determine the spatial variation of surface O3 and its meteorological driving factors in major cities in China, via trend analysis, spatial autocorrelation, hotspot analysis, and multi-scale geographically weighted regression (MGWR) modeling. The results show that: ① during the warm season, O3 concentrations showed a significant growth trend (P<0.05), with an average growth rate of 0.28 μg·(m3·a)-1, while more than 55% of urban O3 concentrations increased by 0.50 μg·m-3 annually. ② There were significant regional differences in O3 concentration. High values (>60 μg·m-3) were distributed over east China, north China, central China, and northwest China, while low values (<20 μg·m-3) were distributed over south China and southwest China. ③ The spatial agglomeration of O3 concentration has been enhanced year by year, with hotspots mainly distributed over east China and central China. In contrast, there are cold spots in northeast China, southwest China, and southern China. ④Analysis of the MGWR model indicated that temperature, wind speed, cloud coverage, and precipitation all have a significant effect on the distribution of O3, although there are also discrepancies in driving factor priorities between the different regions. Temperature was the main meteorological driving factor of O3 variation during the warm season in China, and its impact on O3 concentration was significantly higher in north China, northwest China, and northeast China than in other regions; overall, there was a significant positive correlation between O3 concentration and temperature, except in Guangxi, Yunnan, and Jiangxi. O3 concentration was negatively correlated with wind speed in most regions of south China, east China, and central China, and positively correlated with wind speed in north China and northeast China. O3 concentration was significantly negatively correlated with cloud cover, except in Liaoning, Shandong, Hebei, Gansu, Guangdong, and some areas in southwest China. O3 concentration was significantly negatively correlated with precipitation, except in the northwest and southwest regions.