A new correlation between global solar radiation and the quality of sunshine duration in China

Abstract

Accurate and reliable solar radiation models are important in the building energy conservation, solar thermal and photovoltaic utilization, agricultural production and ecological environment, in which the global solar radiation model based on sunshine percentage is the most common model. Sunshine duration only reflects the time accumulation of solar radiation, but cannot reflect its intensity accumulation. Therefore, it is difficult to improve the accuracy of such models. To solve this problem, a new quality of sunshine duration model (QSD model) is proposed, which takes into account both the influence of sunshine duration on solar radiation and the effect of solar radiation intensity on the accumulation of day. The QSD model is simplified from the energy balance equation which is established based on theoretical analysis of the heat transfer process among the Earth's surface layer, air layer and atmospheric layer. Then Meteorological data of 24 stations are utilized to analyze the accuracy of QSD model. The results show that the QSD model is more accurate, and the accuracy of QSD model is best during sunny days, followed by cloudy days, whereas overcast days provide the worst results. Meanwhile, a QSD model is obtained based on data from different regions. Statistical analysis shows that a QSD model has universal applicability in China, and the average value of correlation coefficient (R) is 0.929, Nash-Sutcliffe equation (NSE) is 0.864, and root mean squared error (RMSE) is 0.088.