Biomass burning aerosol over the Amazon: analysis of aircraft, surface and satellite observations using a global aerosol model

This is the authors' abstract. We don't add key points for this paper.

Vegetation fires emit large quantities of aerosol to the atmosphere impacting regional air quality and climate. Previous work has used comparisons of simulated and observed aerosol optical depth (AOD) in regions heavily impacted by fires to suggest emissions of aerosol particles from fires may be underestimated by a factor of 2–5. Here we use surface, aircraft and satellite observations made over the Amazon during September 2012 along with a global aerosol model to improve understanding of aerosol emissions from vegetation fires. We apply three different satellite-derived fire emission datasets (FINN, GFED, GFAS) in the model. Aerosol emissions in these datasets vary by up to a factor 4 over the Amazon during this period, highlighting the considerable uncertainty in emissions. We find variable agreement between the model and observed aerosol mass concentrations. The model well reproduces observed aerosol concentrations in some periods over deforestation fires in the western Amazon. In contrast, the model underestimates aerosol concentrations over savannah fires in the eastern Amazon. The model consistently underestimates AOD compared to satellite and ground stations, even when the model reproduces the observed vertical profile of aerosol mass concentration. We suggest this is likely caused by uncertainties in the calculation of AOD, with the largest sensitivity due to uncertainty in water uptake. We therefore caution against using comparison with AOD to constrain particulate emissions from fires.