利用NPP/VIIRS微光数据反演夜间气溶胶光学厚度

Aerosol has an extensive impact on Earth's climate and ecosystems and thus harmful to human health. The distribution of atmospheric aerosols has diurnal variation, and nighttime aerosol concentrations are higher than those during the day. Therefore, the accurate monitoring of AOD at night is significant but challenging. The Visible/Infrared Imager/Radiometer Suite (VIIRS) of Suomi National Polar-orbiting Partnership has a Day Night Band (DNB), which can observe the city light overnight. The artificial night light observed by the DNB of VIIRS reflects the extinction effect of the atmosphere and it is helpful in obtaining the nighttime AOD.To monitor the nighttime AOD, this study obtained the nighttime AOD on the basis of the theory of atmospheric radiation transmission. First, moonless and cloudless DNB data were selected, and the artificial lights during the crescent period were obtained by multi-day DNB data fusion. Second, the nighttime AOD was retrieved based on the extinction effect of aerosol on artificial lights. Finally, the obtained AOD is compared with the AOD from the CE318 and AQI indices from the environmental quality monitoring station to verify the feasibility of the retrieval method.This study focused on the nighttime AOD in North China from March 2016 to February 2017. The artificial lights of North China from four seasons were obtained, indicating that the major cities, especially the JingJinJi urban agglomeration, are very prominent in the artificial lights distribution map, and the traffic network between cities is clearly visible. Meanwhile, the nighttime AOD distribution during two heavily polluted weather processes in July and October 2016 was retrieved. The retrieval results indicate that the nighttime aerosols in North China are mainly distributed in the JingJinJi region and the provincial capital, which have developed industries and a dense population. Moreover, the retrieved and observed AODs are consistent, with an agreement index of up to 0.962, indicating that the retrieval study achieved good results.This study demonstrates the potential of satellite twilight data in monitoring the spatial distribution of urban pollution at night. The distribution characteristics of nighttime urban lights and aerosols are also provided, enriching the understanding of the temporal and spatial distribution of aerosols at night.