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In a new weekly update for pv magazine , Solcast, a DNV company, reports that aerosols from Brazilian wildfires significantly reduced solar irradiance in parts of South America in July, although a persistent high pressure system over the South Pacific increased irradiance in Chile and Argentina.
According to analysis using the Solcast API, large areas of northern Brazil recorded +10% higher irradiance than normal in July, while parts of Uruguay, Argentina and Chile recorded up to 20% higher than normal. However, wildfires in Brazil were much more intense than usual in July, with more fires recorded than in almost 20 years. Smoke affected irradiance in southern Brazil, while stable weather in western regions increased irradiance in the north of the country and its high concentration of solar assets north of Rio de Janeiro.
The wildfires in Brazil, fuelled by exceptionally dry conditions, positive temperature anomalies and strong winds, led to a dramatic increase in aerosol levels across South America. These aerosols, which absorb and scatter sunlight, led to a marked reduction in solar irradiance. The impact was widespread, with aerosol plumes travelling southeastwards, affecting areas far beyond the Amazon basin. This can be seen in the ‘clear sky irradiance’ anomaly shown below. Clear sky irradiance measures the available irradiance before accounting for cloud cover.
The number of wildfires in Brazil soared in July, with the number of fires since the beginning of the year nearly 20 times higher than those recorded in the same period in 2023. A combination of near-zero average daily rainfall and high temperatures has fueled out-of-control fires and contributed to one of the most severe declines in “clear sky” irradiance observed in recent years.
In contrast, the South Pacific High – a persistent high-pressure system located west of Chile – caused a significant increase in solar irradiance in Chile and Argentina. This stronger-than-usual high-pressure ridge stabilized the atmosphere, suppressing cloud formation and reducing precipitation in these regions. As a result, irradiance levels increased by up to 20% compared to the July average, providing a substantial boost to solar energy production. Average daily rainfall was also reduced by approximately half, reinforcing dry and clear conditions favorable for solar generation.
However, the southern tip of South America experienced cooler temperatures and lower solar irradiation due to winds coming from further south than usual. These winds brought cold air from the polar regions to the continent, causing average temperatures to drop by up to 6°C in parts of Chile, Argentina, Paraguay and Bolivia. Stronger-than-usual easterly winds in southern Chile, combined with strong anticyclonic winds surrounding the South Pacific, drove moist Pacific air inland. This led to increased rainfall and a 10% to 20% decrease in solar irradiation in the affected southern regions.
Solcast produces these figures by tracking clouds and aerosols at 1-2 km resolution on a global scale, using satellite data and proprietary AI/ML algorithms . This data is used to drive irradiance models, allowing Solcast to calculate irradiance at high resolution, with a typical bias of less than 2%, and also cloud tracking forecasts. This data is used by over 300 companies managing over 150 GW of solar assets worldwide. |
