Observations and tracing of air quality during the Beijing Winter Olympic Games using Chinese satellite hyperspectral measurements

In September 2021, China's Gaofen-5B satellite carrying the environmental trace gas monitoring instrument (EMI) was successfully launched, which promoted the self-directed development of remote sensing monitoring in China. During the Beijing-Zhangjiakou Winter Olympics, we used the satellite product to provide remote sensing data support for air quality assurance at the Winter Olympics. This paper introduced the domestic hyperspectral satellite product of tropospheric NO2 retrievals, analysed the spatial and temporal distribution of NO2 pollution in Beijing and its surrounding key cities during the 2022 Winter Olympic Games from January to March, and further discussed the influence of meteorological conditions and anthropogenic emission control measures on the atmospheric NO2 concentration during the Winter Olympic Games. The results showed that the average tropospheric NO2 column concentration in North China during the Winter Olympics was approximately 3.75x10(15) molecules/cm(2), which was significantly lower than that before and after the Winter Olympics. NO2 concentrations in major cities decreased between 53.14% and 70.07%, indicating that the temporary control policy during the Winter Olympics had a significant effect. However, the implementation of the policy varies in different cities, which is consistent with the in situ measurements of NO2 concentration by the national air quality sites. High concentrations of tropospheric NO2 occurred on two days during the event, mainly due to unfavourable wind fields. Moreover, a generalized additive model was established to distinguish and quantify the contribution of meteorological and anthropogenic factors to the change in tropospheric NO2 concentrations. For example, the decreases in NO2 concentrations in Baoding, Beijing, Tianjin and Taiyuan during the event were 48.2%, 67.5%, 48.8% and 72.8%, respectively, and emission controls and meteorology contributed 41.8%, 32.0%, 30.0%, 42.8% and 6.4%, 35.6%, 18.8%, 30.1%, respectively. In general, the influence of meteorological factors on the sharp decrease in NO2 concentration was significantly weaker than the temporary measures of NOX emission control. Satellite air quality monitoring revealed the spatial and temporal variations in air pollutants during the event. Further analysis based on the GAM model can evaluate the effectiveness of air quality control measures and benefit environmental policy-makers.