PNNL

Abstract

Absorbing aerosols emitted from biomass burning play an essential role in affecting the radiation balance, cloudiness, and atmospheric circulation over tropical regions. Assessments of these impacts rely heavily on the modeled aerosol absorption from poorly constrained global models and thus exhibit large uncertainties. By combining the AeroCom global model ensemble with satellite and in situ observations, we provide new constraints on the aerosol absorption optical depth (AAOD) over the Amazon and Africa. Our approach enables identifying, for each model, error contributions from emission, lifetime, and MAC (mass absorption coefficient), with MAC and emission dominating the modeled AAOD errors over Amazon and Africa, respectively. In addition to primary emissions, our analysis suggests substantial formation of secondary organic aerosols over the Amazon but not over Africa, which contributes to the modeled AAOD errors. Furthermore, we find that difference in the direct aerosol radiative effects between models decrease by threefold after correcting for the identified errors. This highlights the potential to significantly reduce the uncertainty in the most uncertain radiative forcing agent.