Satellite (GOSAT-2 CAI-2) retrieval and surface (ARFINET) observations of aerosol black carbon over India

Abstract

Light-absorbing black carbon (BC) aerosols strongly affect Earth's radiation budget and climate. This paper presents satellite retrieval of BC over India based on observations from the Cloud and Aerosol Imager-2 (CAI-2) on board the Greenhouse gases Observing Satellite-2 (GOSAT-2). To evaluate and validate the satellite retrievals, near-surface BC mass concentrations measured across the Aerosol Radiative Forcing over India NETwork (ARFINET) of aerosol observatories are used. Then the findings are extended to elucidate global BC features. The analysis reveals that this satellite retrieval clearly demonstrates the regional and seasonal features of BC over the Indian region, similarly to those recorded by surface observations. Validation and closure studies between the two datasets show RMSE < 1 and absolute difference below 2 µg m−3 for > 60 % of simultaneous observations, exhibiting good associations for December, January, and February (R of approximately 0.73) and March, April, and May (R approx. 0.76). Over the hotspot regions of India, satellite retrievals show a soot volume fraction of approx. 5 %, columnar single-scattering albedo of approx. 0.8, and BC column optical depth of approx. 0.1 during times of the highest BC loading, which are comparable to other in situ and satellite measurements. In terms of global spatiotemporal variation, satellite retrievals show higher BC occurring mostly in areas where biomass burning is intense. Overall, this study highlights the effectiveness of satellite retrieval of BC, which can be used effectively for the regular monitoring of BC loading attributable to vehicular, industrial, or biomass burning activities.