Evaluation of WRF shortwave radiation parameterizations in predicting Global Horizontal Irradiance in Greece

This study aims at assessing the differences induced in the Global Horizontal Irradiance (GHI) predictions by the mesoscale atmospheric Weather Research and Forecasting (WRF) model when using different shortwave radiation. Model predictions are compared with GHI measurements at 12 stations of the Hellenic Network of Solar Energy (HNSE) for January, April, July and October 2013. The shortwave radiation schemes that were evaluated are: the Dudhia, the updated Rapid Radiative Transfer Model (RRTMG), the updated Goddard and the Goddard Fluid Dynamics Laboratory (GFDL) schemes. All schemes perform better under cloudless conditions due to limited ability of the WRF model to simulate cloudy conditions. The Dudhia scheme performs best with mean relative difference of 2.2 ± 15% for clear-skies, while the differences for the other schemes range between 5 and 12% with similar standard deviations. For all-skies, the model-derived hourly GHI is overestimated for all schemes (∼40–70%).