An improved technique for global solar radiation estimation using numerical weather prediction

• A new model for hourly global solar radiation modelling is proposed.
• Model makes use of upper air information from MM5 at various altitudes.
• The new model outperforms the existing model of Yang and Koike (2002).
• Nash–Sutcliffe (1970) model efficiency was 0.81 for the new model for hourly scale.
• Comparison was also made for daily and monthly scales.

Global solar radiation is the driving force in hydrological cycle especially for evapotranspiration (ET) and is quite infrequently measured. This has led to the reliance on indirect techniques of estimation for data scarce regions. This study presents an improved technique that uses information from a numerical weather prediction (NWP) model (National Centre for Atmospheric Research NCAR's Mesoscale Meteorological model version 5 MM5), for the determination of a cloud cover index (CI), a major factor in the attenuation of the incident solar radiation. The cloud cover index (CI) together with the atmospheric transmission factor (KT) and output from a global clear sky solar radiation were then used for the estimation of global solar radiation for the Brue catchment located in the southwest of England. The results clearly show an improvement in the estimated global solar radiation in comparison to the prevailing approaches.