Difference between forward- and backward-looking bands of GOSAT-2 CAI-2 cloud discrimination used with Terra MISR data

Abstract

Greenhouse gases Observing SATellite-2 (GOSAT-2) will be launched in fiscal year 2017. GOSAT-2 will be equipped with two Earth-observing instruments: the thermal and near-infrared sensor for carbon observation Fourier transform spectrometer 2 (TANSO-FTS-2) and TANSO-cloud and aerosol imager 2 (CAI-2). The FTS-2 data will be used to determine atmospheric concentrations of greenhouse gases, such as CO2 (carbon dioxide), CH4 (methane) and CO (carbon monoxide). CAI-2 is a push-broom imaging sensor that has forward- and backward-looking bands for observing the optical properties of aerosols and clouds, and for monitoring the status of urban air pollution and transboundary air pollution over oceans. An important role of CAI-2 is to perform cloud discrimination in each direction. The Cloud and Aerosol Unbiased Decision Intellectual Algorithm (CLAUDIA) will be used for cloud discrimination with CAI-2. The Multi-angle Imaging Spectroradiometer (MISR) aboard the Terra spacecraft provides radiometrically and geometrically calibrated images for spectral bands at nine widely spaced angles. In this study, we examined the difference between forward and backward cloud discrimination by using CLAUDIA with Terra MISR data. The results were as follows: (1) in land areas and polar regions, cloud discrimination results obtained with either band could be used; and (2) in sea areas, cloud discrimination results that include no-sun-glint regions should be used.