A New Benchmark for Surface Radiation Products over the East Asia-Pacific Region Retrieved from the Himawari-8/AHI Next- Generation Geostationary Satellite

Surface downward radiation (SDR), including shortwave downward radiation (SWDR) and longwave downward radiation (LWDR), is of great importance to energy and climate studies. Considering the lack of reliable SDR data with a high spatiotemporal resolution in the East Asia-Pacific (EAP) region, we derived SWDR and LWDR at 10-min and 0.05 resolutions for this region from 2016 to 2020 based on the next-generation geostationary satellite Himawari-8 (H-8). The SDR product is unique in terms of its all-sky features, high accuracy, and high-resolution levels. The cloud effect is fully considered in the SDR product, and the influence of high aerosol loadings and topography on the SWDR are considered. Compared to benchmark products of the radiation, such as Clouds and the Earth's Radiant Energy System (CERES) and the European Centre for Medium-Range Weather Forecasts (ECMWF) next-generation reanalysis (ERA5), and the Global Land Surface Satellite (GLASS), not only is the resolution of the new SDR product notably much higher, but the product accuracy is also higher than that of those products. In particular, hourly and daily root-mean-square errors of the new SWDR are 104.9 and 31.5 W m^-2, respectively, which are much smaller than those of CERES (at 121.6 and 38.6 W m^-2, respectively), ERA5 (at 176.6 and 39.5 W m^-2, respectively), and GLASS (daily of 36.5 W m^-2). Meanwhile, RMSEs of hourly and daily values of the new LWDR are 19.6 and 14.4 W m^-2, respectively, which are comparable to that of CERES and ERA5, and even better over high-altitude regions.