Application of GOSAT TANSO-CAI observations for aerosol optical depth retrieval and surface PM2.5 air quality monitoring
Abstract:This paper describes the algorithm to retrieve Aerosol Optical Depth (AOD) from data acquired by the Thermal And Near infrared Sensor for carbon Observation Cloud and Aerosol Imager (TANSO-CAI), onboard Greenhouse gases Observing SATellite (GOSAT). TANSO-CAI has four spectral bands, namely, 0.380μm (Band 1), 0.674μm (Band 2), 0.870μm (Band 3), and 1.60μm (Band 4). Its measurements at the near-ultraviolet band (0.380μm) at 0.5 km resolution make it ideal for retrieving AOD and monitoring surface PM air quality over urban regions because surface reflectance generally is much lower in UV than in the visible.
The AOD retrieval algorithm is based on a look up table method in which the reflectance at the top of atmosphere is computed from UNL-VRTM (UNified Linearized Vector Radiative Transfer Model) as a function of surface reflectance, aerosol scattering properties, and Sun-Satellite-Earth geometries. Surface reflectance at 380 nm with high spatial resolution is derived from the climatology based on the MODIS 16 days of BRDF parameters dataset (MCD43A1) and extrapolation. The retrieval is evaluated with MODIS and AERONET AOD. Comparison of our retrieved AOD and surface PM2.5 indicate the high potential of using TANSO-CAI for air quality applications.