[A-CG36] 静止軌道衛星による陸面観測

[ACG36-04] Evaluation of Himawari-8/AHI surface reflectance using LEO sensors with off-nadir observation mode for terrestrial monitoring applications

*BEICHEN ZHANG¹、Kazuhito Ichii¹、Wei Li¹、Yuhei Yamamoto¹、Wei Yang¹、Ram Sharma¹、Hiroki Yoshioka²、Masayuki Matsuoka³、Tomoaki Miura⁴ (1.Center for Environmental Remote Sensing (CEReS), Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan、2.Department of Information Science and Technology, Aichi Prefectural University, 1522-3 Ibaragabasama,Nagakute, Aichi 480-1198, Japan、3.Department of Information Engineering, Mie University, 1577 Kurimamachiya, Tsu, Mie 514-8507, Japan、4.Department of Natural Resources and Environmental Management, University of Hawai‘i at Mānoa, 1910 East-West Road, Honolulu, HI 96822, USA)

キーワード：Himawari-8 AHI, Terra MISR, atmospheric correction, surface reflectance, GEO-LEO inter-comparison

Third generation geostationary satellites (3^rd-GEO) have the potential for terrestrial monitoring owing to their innovations in spatial, spectral and temporal resolution, and are already being used to study land surface changes. Surface reflectance (SR) is one of the most fundamental products among land surface physical variables. Yet, evaluation methods for 3^rd-GEO's SR remain to be refined. Typical Low Earth Orbit (LEO) sensors, such as MODIS and VIIRS, have been widely employed for inter-comparison between LEO and GEO SRs, using their products as a reference. However, matching conditions of sun-sensor geometries were unavailable in mid-latitudes. In this study, the off-nadir observed LEO sensor datasets are used to match with Himawari-8/AHI at mid-latitudes by similar geometric observation conditions, to provide evaluation approaches for 3^rd-GEO terrestrial monitoring. We implemented this idea using the ray-matching method and a forward-backward observed sensors (i.e., Terra/MISR). The results show that areas screened with matching data pairs within the AHI full disk region cover the mid-latitude region. At several selected regions of interest (ROIs), a sufficient number of AHI-MISR matches were available over 3 years (2017-2019). Based on their matching data pairs, the estimated AHI's SR by 6SV (the vector version of the second simulation of a satellite signal in the solar spectrum) model is in well agreement with the MISR's SR product (r>0.75), either in forest or non-forest ROIs, under clear-sky conditions. We expect to obtain reliable 3^rd-GEO products for high frequency terrestrial monitoring by this method.