[세미나] 박록진 교수님

A global simulation of organic aerosols: Implications for climate and air quality

A global simulation of organic aerosols: Implications for climate and air quality

Recent observations suggest that a certain fraction of organic aerosol (OA) effectively absorbs solar radiation especially at the visible wavelengths. This OA fraction is called brown carbon aerosol. However, few global models include this OA species, in which a constant mass ratio to other carbonaceous species is used to calculate its global concentrations. Here we provide an explicit global simulation of brown carbon aerosol using the GEOS-Chem model, driven by the assimilated meteorological data. We first estimate global emissions of brown carbon aerosol from biofuel use and biomass burning using emission factors depending on burning efficiencies from the literature. Based on chamber studies, secondary organic aerosols (SOAs) produced by oxidation of aromatic species are also considered as brown carbon aerosol in our model. We evaluate our model by comparing with in-situ observations in the surface air in the U.S. and with absorbing aerosol optical depths at AERONET sites. The model successfully reproduces the observed seasonal variations but appears to underestimate the magnitudes especially in the regions where SOAs concentrations are dominant. Our global simulations show that brown carbon accounts for about 20% of total organic aerosols, which are previously assumed to be scattering aerosols. Consideration of solar absorption by brown carbon in the model considerably offsets the cooling by OA aerosols. In addition, the effect of this absorption on photolysis rates has caused non-negligible modification of oxidant concentrations especially in East Asia.