Improving estimation of hourly, daily, and monthly solar radiation by importing global data sets

Surface solar radiation is an important parameter in hydrological models and crop yield models. This study developed a model to estimate solar radiation from sunshine duration. The model is more accurate and more general than traditional Ångström–Prescott models. It can explicitly account for radiative extinction processes in the atmosphere. Moreover, global data sets that describe the spatial and temporal distribution of ozone thickness and Ångström turbidity were introduced in the model to enhance its universal reliability and applicability. The model was calibrated in lowland and humid sites and validated at a number of sites in various climate and elevation regions. The new model shows overall better performances than three Ångström–Prescott models. Because this model follows the simple form of the Ångström–Prescott model, and its inputs (sunshine duration, air temperature, and relative humidity) are accessible from routine surface meteorological observations, it can be easily applied to hydrological and agricultural studies. The source code and the auxiliary data of the model are available from the authors upon request.