Historic 2024 South American Wildfires Season Rages

Authors: Allie Collow, Carl Mallings, Joe Ardizzone, Emma Knowland, Bennett Erdman

South America has experienced widespread wildfires since mid-July, the highest concentration being in Bolivia and Brazil. Lasting over 2 months in some instances, these fires have expelled vast quantities of smoke into the atmosphere and, due to prevailing winds aloft, have led to “atmospheric aerosol rivers.” Visible below, these plumes of suspended particles exemplify how wildfire outbreaks can affect not just the areas immediately around the burned area, but downwind as well. Around the time of these figures – September 12, 2024, at 16 UTC – Sao Paulo, Brazil experienced the worst air quality in the world.

slide graphic from TC Akara
Figure 1: GEOS-FP Analysis of the South American wildfires, on September 12, 2024 at 16 UTC. The combined effects of aerosols from these wildfires and solar radiation are evident in the left panel, which shows total shortwave radiation forcing due to aerosols. The high concentration of smoke (shown in right panel) traps shortwave solar radiation, increasing total radiative forcing levels. This flux in shortwave radiation forcings is on a diurnal cycle.

One consequence of wildfire smoke is aerosols suspended in the atmosphere trap more shortwave (solar) radiation which, in large enough quantities, increases temperatures. The figure’s left panel shows total shortwave forcing due to aerosols, measured in W/m2, as captured by GEOS-FP Analysis. Areas of highest forcing are depicted in blue, with values exceeding 600 W/m2 of additional solar radiation. The right panel shows carbon monoxide (CO) aloft as a result of biomass burning, depicted by GEOS Analysis, as well as surface locations with elevated CO, sourced from MODIS QFED. Column concentrations exceeding 1018 molecules per cm2 are shown in orange and yellow. ​

slide graphic from TC Akara
Figure 2: Daily (left) and total accumulated (right) carbon monoxide (CO) emissions from burning biomass in Bolivia and Brazil, measured in kg/m2. Red lines depict respective values for 2024 in both figures, showing that this year's wildfire season surpassed maximum values for both daily CO emissions and total accumulated CO emissions recorded from 2003-2023. The former of these saw values nearly double observed maximums in the previous 20 years.

The animation below shows the progression of the 2024 fire season from June 1 through September 30 using GEOS Analysis. This video depicts both the diurnal cycle of shortwave forcing due to aerosols, and the high concentration of said aerosols as a result of biomass burning (though the left panel shows total shortwave forcing due to all aerosols, and the right panel only shows CO). The highest values are present in mid-August through mid-September. The combination of the size of the fires and prevailing winds resulted in smoke being transported both far distances and in high concentrations, making the fires' effects felt far from the actual sources. Though the peak of the 2024 fire season has passed, fires still persist in parts of South America.

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