Aggravated surface O3 pollution primarily driven by meteorological variation in China during the early COVID-19 pandemic lockdown period
Abstract. Due to the lockdown during the COVID-19 pandemic in China from late January to early April in 2020, a significant reduction of primary air pollutants has been identified by satellite and ground observations. However, this reduction is in contrast with the increase of surface O3 concentration in many parts of China during the same period. The reasons for this contrast are studied here from two perspectives: emission changes and inter-annual meteorological variations. Based on top-down constraints of NOx emissions from TROPOMI measurements and GEOS-Chem model simulations, our analysis reveals that NOx and volatile organic compound (VOC) emission reductions as well as meteorological variations lead to 8 %, -3 %, and 1 % changes in O3 over North China, respectively. In South China, however, we find that meteorological variations cause ~30 % increases in O3, which is much larger than -1 % and 2 % changes due to VOC and NOx emission reductions, respectively, and the overall O3 increase is consistent with the surface observations. The higher temperature is the main reason that leads to the surface O3 increase in South China. Overall, inter-annual meteorological variations have a larger impact than emission reductions on the aggravated surface O3 pollution in China during the early lockdown period of COVID-19 pandemic.
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