Improving Nighttime Aerosol Optical Depth Retrieval with the VIIRS Day/Night Band

The Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB), which can be used to detect artificial light source coming from the Earth's surface, has been applied in air quality studies. Using observation data from VIIRS DNB, a new variance method algorithm has been proposed to retrieve the nighttime aerosol optical depth (AOD) at different box (NN (N=3, 5, 7, 9, 11, 13) pixels) resolutions. Because of lack of DNB surface reflectance over much wider range of wavelengths, we inherit the empirical reflectance relationship from the Moderate Resolution Imaging Spectroradiometer (MODIS) and use the VIIRS and MODIS spectral response functions to establish the relationship more suitable for VIIRS. The quantitative relationship between the satellite viewing zenith angle (VZA) and the Upwelling Radiance from Artificial Light Sources (Ia) is determined using the zenith-radiance quadratic (ZRQ) model. Ultimately, to reduce the uncertainty of inversion, appropriate pixels (Quality Assurance confidence (QAC): 0 (all quality) and 1 (good quality)) are selected for the AOD inversion. The results show that our AOD products can better reflect the regional characteristics with the VIIRS sensor. In addition, we have evaluated the VIIRS/DNB-retrieved AOD against Aerosol RObotic NETwork (AERONET) AOD and Micro Pulse Lidar (MPL) AOD. The comparison results exhibit a high correlation, which are higher when Box > 5×5 and QAC = 1 (R(AOD_DNB vs. AOD_AERO)>0.8 and R(AOD_DNB vs. AOD_MPL)>0.6).