Global Horizontal Irradiance in West Africa: Evaluation of the WRF-Solar Model in Convective Permitting Mode with Ground Measurements

Abstract

The number of solar power plants has increased in West Africa in recent years. Reliable reanalysis data and short-term forecasting of solar irradiance from numerical weather prediction models could provide an economic advantage for the planning and operation of solar power plants, especially in data-poor regions such as West Africa. This study presents a detailed assessment of different shortwave (SW) radiation schemes from the Weather Research and Forecasting option Solar (WRF-Solar) model with appropriate configurations for different atmospheric conditions in Ghana and the southern part of Burkina Faso. We applied a two one-way nested domain (D1=15 km and D2=3 km) to investigate four different SW schemes namely, CAM, Dudhia, RRTMG, Goddard and RRTMG without aerosol and with aerosol inputs (RRTMG_AERO). The simulation results were validated using hourly measurements from different automatic weather stations established in the study region in recent years. The results show that the RRTMG_AERO_D01 generally outperforms the other SW radiation schemes to simulate GHI under all-sky condition (RMSE=235 W/m2 (19%); MAE=172 W/m2 (14%)) and also under cloudy skies. Moreover, RRTMG_AERO_D01 shows the best performance on a seasonal scale. Both the RRTMG_AERO and Dudhia experiments indicate a good performance under clear skies. However, the sensitivity study of different SW radiation schemes in the WRF-Solar model suggests that RRTMG_AERO gives better results. Therefore, it is recommended to use it for solar irradiance forecasts over Ghana and the southern part of Burkina Faso.