Estimation and forecast of solar radiation in the Aburra Valley- Colombia

The diagnostic and forecast of the surface solar irradiance are important elements for the harnessing of solar energy. By validating against in situ measurements, this study assessed the skill of the ERA5 reanalysis, the GOES16 satellite estimates, and the forecasts from the Weather Research and Forecasting model (WRF) for a site in the Aburra Valley. The analysis focuses on the diurnal cycle, the seasonal behavior, and the inter-annual variations of the estimates of surface solar irradiance and daily accumulated energy. In general, the reanalysis yielded estimates closer to the observations compared to GOES16. At the daily scale, ERA5 exhibited smaller biases (0.01 to 1.05 kWh/) than the GOES16 estimates (-1.23 to 1.07 kWh/). The ERA5 estimates showed that the solar radiation was higher during El Nino events, especially during the December-January-February season, with an average increase of about 10% compared to the neutral and La Nina conditions. On the other hand, similar to other studies, the WRF forecasts exhibited mean bias errors (MBE) of around 20%, and root mean squared errors (RMSE) of about 50%. Furthermore, the correlation analysis showed that the WRF correctly represents the hourly and day to day variations of solar irradiance with correlation values of around 0.86 and 0.81, respectively. Both the diagnostic estimates from ERA5 and GOES16, as well as the WRF forecasts, showed the largest biases during cloudy and rainy days and seasons.