Estimation of nighttime aerosol optical thickness from Suomi-NPP DNB observations over small cities in Korea

Abstract : In this study, an algorithm to estimate Aerosol Optical Thickness (AOT) over small citiesduring nighttime has been developed by using the radiance from artificial light sources in small citiesmeasured from Visible Infrared Imaging Radiometer Suite (VIIRS) sensor’s Day/Night Band (DNB)aboard the Suomi-National Polar Partnership (Suomi-NPP) satellite. The algorithm is based on Beer’sextinction law with the light sources from the artificial lights over small cities. AOT is retrieved for cloud-free pixels over individual cities, and cloud-screening was conducted by using the measurements fromM-bands of VIIRS at infrared wavelengths. The retrieved nighttime AOT is compared with the aerosolproducts from MODerate resolution Imaging Spectroradiometer (MODIS) aboard Terra and Aquasatellites. As a result, the correlation coefficients over individual cities range from around 0.6 and 0.7between the retrieved nighttime AOT and MODIS AOT with Root-Mean-Squared Difference (RMSD)ranged from 0.14 to 0.18. In addition, sensitivity tests were conducted for the factors affecting the nighttimeAOT to estimate the range of uncertainty in the nighttime AOT retrievals. The results of this study indicatethat it is promising to infer AOT using the DNB measaurements over small cities in Korea at night. Afterfurther development and refinement in the future, the developed retrieval algorithm is expected to producenighttime aerosol information which is not operationally available over Korea.Key Words : Aerosol, Nighttime Aerosol Optical Thickness, Day Night Band요약 :