Estimation and Evaluation of Land Surface Reflectance from a Next-Generation Geostationary Meteorological Satellite, Himawari-8/9 AHI

抄録

 Himawari-8/9 is a next-generation Japanese Geostationary Earth Orbit (GEO) meteorological satellite with an onboard sensor – the Advanced Himawari Imager (AHI). Because Himawari-8/9 AHI observe the Earth's hemispheres every 10 min with multiple spectral bands, AHI providing an unprecedented opportunity to facilitate its observation datasets are expected to be a new data source for terrestrial monitoring in terms of mitigating cloud contaminations. Estimation of land surface reflectance (LSR) is crucial in quantitative terrestrial monitoring. In this study, we aimed to develop a method for estimating the LSR and angular-adjusted LSR of the Himawari-8/9 AHI using the look-up table based Second Simulation of a Satellite Signal in the Solar Spectrum Vector (6SV) Radiative Transfer Model (RTM) and kernel-driven semi-empirical bidirectional reflectance distribution function (BRDF) model. The estimated LSR underwent evaluation and inter-comparison through two distinct approaches: ray-matching and estimating angular-adjusted LSR. Ray-matching of the obtained data pairs with the MODIS LSR product shows that the correlation coefficients (r) for all bands are greater than 0.86 at low latitudes. Angular-adjusted LSRs estimated using AHI time-series data at mid-latitudes also show good agreement with MODIS (r > 0.5), particularly the red and near-infrared bands (r > 0.9). The results obtained by our method are in high agreement with those calculated using the reference aerosol optical thickness (AOT) (r > 0.98). Our findings highlight the potential application of our methodology to other GEO satellites for high-frequency terrestrial monitoring at continental to global scales.