Estimates of high spatiotemporal resolution solar shortwave radiation from Himawari-8 radiation products in mountainous areas

Downward surface shortwave radiation (DSSR) is an important parameter of the global energy balance. DSSR is affected by the interaction of atmospheric and terrain effects, making it difficult to obtain solar shortwave radiation with high spatiotemporal resolution in mountainous areas. In this study, based on the radiation product of the geostationary satellite Himawari-8 (H-8) radiation product (10 min 5 km), terrain correction coefficients (TCCs) were developed and incorporated into the spatial downscaling method to estimate high-resolution DSSR. The upper and middle reaches (UM-HRB) of the Heihe River Basin were selected for verification, using data from nine ground observation stations. The H-8 downscaled DSSR have a high correlation with ground-based observations, based on 7,214 observations over 17 days in 2021 under clear-sky conditions. The coefficient of determination (R 2 ) exceeded 0.93, the mean bias error (MBE) and root mean square error (RMSE) were 8.17 W/m 2 and 74.25 W/m 2 . Based on 9,344 observations over 17 days in 2021 under all-sky conditions, the R 2 exceeds 0.90. the MBE and the RMSE were 74.02 W/m 2 and 103.38 W/m 2 . Under all-sky conditions, although the cloudy period estimates differ from the ground-based observations, the all-day trend is basically consistent with the ground-based observations. These results demonstrate that combining spatial downscaling with TCCs can effectively estimate DSSR in mountainous areas. • Obtain high spatiotemporal resolution DSSR in mountainous areas, and improve the accuracy of DSSR estimation in mountainous areas. • TCCs were introduced into the spatial downscaling method to estimate the DSSR. • Taking into account direct radiation, scattered radiation, and reflected radiation from the surrounding terrain