A Remote Sensing Model to Estimate Sunshine Duration in the Ningxia Hui Autonomous Region, China

Sunshine duration (SD) is strongly correlated with solar radiation, and is most widely used to estimate the latter. This study builds a remote sensing model on a 100 m × 100 m spatial resolution to estimate SD for the Ningxia Hui Autonomous Region, China. Digital elevation model (DEM) data are employed to reflect topography, and moderate-resolution imaging spectroradiometer (MODIS) cloud products (Aqua MYD06-L2 and Terra MOD06-L2) are used to estimate sunshine percentage. Based on the terrain (e.g., slope, aspect, and terrain shadowing degree) and the atmospheric conditions (e.g., air molecules, aerosols, moisture, cloud cover, and cloud types), observation data from weather stations are also incorporated into the model. Verification results indicate that the model simulations match reasonably with the observations, with the average relative error of the total daily SD being 2.21%. Further data analysis reveals that the variation of the estimated SD is consistent with that of the maximum possible SD; its spatial variation is so substantial that the estimated SD differs significantly between the south-facing and north-facing slopes, and its seasonal variation is also large throughout the year.