Global abundance of strongly-absorbing brown carbon aerosol

Abstract:

Organic aerosols (OAs) consist of scattering and sunlight absorbing ones, and the latter have been referred to as brown carbon (BrC). Some BrC particles are known to be strongly absorbing while others are weakly absorbing. Whether or not strongly-absorbing BrC is wide-spread globally, and its relative amount to total OA are still unknown. We determine the single scattering albedo (SSA) of OA by combining and analyzing AERONET, MODIS and MISR data. Our observational analysis shows that the OA SSA at 550nm should be < 0.85, at least in the tropics. This low OA SSA is much lower than previously used in climate models, and compels strongly absorbing BrC to represent a significant fraction of OAs over the tropics and probably elsewhere.