Light Absorption Properties and Radiative Forcing Impacts of Primary Organic Aerosol Emissions

 

Authors

David George Streets — Argonne National Laboratory
Zifeng Lu — Argonne National Laboratory

Category

Absorbing Aerosol

Description

Organic aerosols (OA) in the atmosphere affect Earth’s energy budget by not only scattering but also absorbing solar radiation due to the presence of the so-called “brown carbon” (BrC) component. However, the absorptivities of OA are not or poorly represented in current climate models. In this study, we provide a method to constrain the BrC absorptivity at the emission inventory level using recent laboratory and field observations. We review available measurements of the light-absorbing primary OA (POA), and quantify the wavelength-dependent imaginary refractive indices (kOA, the fundamental optical parameter determining the particle’s absorptivity) and their uncertainties of the bulk POA emitted from biomass/biofuel, lignite, propane, and oil combustion sources. In particular, we parameterize the kOA of biomass/biofuel combustion sources as a function of the black carbon (BC)-to-OA ratio, implying that the absorptive properties of POA depend strongly on burning conditions. The derived fuel-type-based kOA profiles are incorporated into a global carbonaceous aerosol emission inventory and the integrated kOA values of sectoral and total POA emissions are presented. Results of a simple radiative transfer model show that the POA absorptivity warms the atmosphere significantly and leads to ~27% reduction in the amount of the net global average POA cooling compared to results using the non-absorbing assumption.