The Use of Atmospheric Reanalyses Data for the Estimation of Solar Radiation Considering the Effect of Atmospheric Aerosols

This study focuses on solar energy generation as an alternative source of renewable energy in Brazil, driven by the growing demand in this sector. In recent years, photovoltaic energy technology has undergone significant advancements, resulting in increased efficiency and cost reduction. However, in Brazil, the availability of observed solar irradiance data, essential for validating the generation potential of this form of energy, is extremely limited. Given that in some regions of the country the only available data is extrapolated from weather stations in other locations, this study adopts the approach of using data from meteorological models to fill these gaps. The study focused on using the second generation of the MERRA-2 reanalysis, which has the positive feature of assimilating aerosol data provided by GMAO/NASA, to estimate solar irradiance in tropical and subtropical regions of Brazil. This approach allowed an evaluation of the impact of these scenarios on solar irradiance estimation, validated through observational data collected at surface stations by INMET (National Institute of Meteorology). The variables used from the MERRA-2 reanalysis and analyzed in this work are Surface Net Downward Shortwave Flux (SWGNT), Surface Net Downward Shortwave Flux assuming no aerosol (SWGNTCLN), Surface Net Downward Shortwave Flux assuming clear sky (SWGNTCLR), and Surface Net Downward Shortwave Flux assuming clear sky and no aerosol (SWGNTCLRCLN). Seeking a better understanding of the effects of clouds and aerosols on the solar irradiance of the studied model, data from all regions of Brazil will be considered. Forty-two weather stations were compared with reanalysis data estimates, considering cloud cover and aerosol inclusion. The study revealed a high correlation between observations and the MERRA-2 reanalysis, highlighting the relevance of cloud effects in solar irradiance estimation. MERRA-2 achieved the best results when considering aerosol effects in situations of high concentration, as during the months of September in Campo Grande - MS, one of the regions most affected by fires in the Amazon region.