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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 across parts of South America in July, although a persistent high-pressure system over the South Pacific boosted irradiance in Chile and Argentina.
According to analysis using the Solcast API, large areas of Northern Brazil saw +10% more irradiance than normal for July, while parts of Uruguay, Argentina and Chile saw up to 20% more than normal. However, wildfires in Brazil were much more intense than usual in July, with more fires registered than in nearly 20 years. The smoke impacted irradiance across southern Brazil while stable weather in the western regions brought increased irradiance to the north of the country and its high concentration of solar assets north of Rio de Janeiro.
The wildfires in Brazil, fueled by exceptionally dry conditions, positive temperature anomalies and high winds, caused a dramatic spike in aerosol levels across South America. These aerosols, which absorb and scatter sunlight, resulted in a noticeable reduction in solar irradiance. The impact was widespread, with aerosol plumes traveling southeast, affecting areas far beyond the Amazon basin. This can be seen in the below ‘clear-sky irradiance’ anomaly. Clear sky irradiance measures the available irradiance before cloud cover is taken into effect.
The number of wildfires in Brazil soared in July, with the amount of fires since the start of the year reaching nearly 20 times the figure registered across the same period of 2023. A combination of near-zero daily average rainfall and high temperatures has led to rampant fires and contributed to one of the most severe decreases in ‘clear sky’ irradiance observed in recent years.
In contrast, the South Pacific High – a persistent high-pressure system located west of Chile – led to a significant increase in solar irradiance in Chile and Argentina. This ridge of high pressure, which was stronger than usual, stabilized the atmosphere, suppressing cloud formation and reducing rainfall across these regions. As a result, irradiance levels rose by as much as 20% compared to the July average, providing a substantial boost to solar energy production. Daily rainfall averages were also down by about half, reinforcing the dry, clear conditions favorable for solar generation.
However, the southern tip of South America experienced cooler temperatures and reduced solar irradiance due to winds coming from further south than usual. These winds brought cold air from the polar regions into 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 circling the South Pacific High, directed moist air from the Pacific inland. This led to increased rainfall and a 10% to 20% decrease in solar irradiance in the affected southern regions.
Solcast produces these figures by tracking clouds and aerosols at 1-2km resolution globally, using satellite data and proprietary AI/ML algorithms. This data is used to drive irradiance models, enabling Solcast to calculate irradiance at high resolution, with typical bias of less than 2%, and also cloud-tracking forecasts. This data is used by more than 300 companies managing over 150GW of solar assets globally. |
