Impact Of Different Mixing Ways Of Aerosols On Their Optical Properties And Radiative Forcing

In order to study the impact of mixing ways of aerosols on their optical properties, three different internal mixing models including core-shell model, Maxwell-Garnett model and Bruggeman model plus one external mixing model have been introduced in this article. The optical properties of a variety of single-component aerosol particles and mixed aerosol particles formed by black carbon, sulfate and organic carbon at multiple wavelength bands have been calculated by using Mie theory and combining the observational size distribution at East Asia. The radiative transfer module of BCC-AGCM model has been used to demonstrate the impact of different aerosol mixing ways on the radiative forcing. The results show that aerosol particles formed by different component have unique optical properties within different wavelength bands, and there are great differences of optical properties of mixing particles obtained by each models except Maxwell-Garnett model&Bruggeman model (difference less than2%). Comparing with external mixing model, internal mixing models lead to an increase of the mass absorption factors (Qa) of mixed particles by about20%and a decrease of the mass scattering factors (Qs) of mixed particles by10%～15%at the most cases, while causing a largest enhancement of the mass extinction factors (Qe) of mixed particles by25%. Internal mixing model causes a significant reduction of single scattering albedo (SSA). In particular, internal mixing models increase about20%of absorption in the role of extinction in the case of relatively small volume of black carbon (under30%) and high relative humidity (above70%). In addition, optical properties of mixed particles, except the asymmetry parameter (ASY), are distinctly related to the change of volume ratio or relative humidity. Sensitivity experiment uses the global black carbon aerosol mass concentration. The results show that comparing to external mixing type; internal mixing type gives a enhancement of20%on radiative forcing of black carbon-sulfate aerosol. Depending on different mixing modles, the black carbon-sulfate aerosol causes radiative forcing by-0.6--0.75W/m2on the ground surface downstream radiation flux; the aerosol also have a weakening effect of-0.43～-0.55W/m2on the upstream radiation flux. In summary, the ground surface net radiation flux increases for0.15～0.25W/m2by the effect of black carbon-sulfate aerosol, which leads to a atmosphere heating rate of10"2K/day orders of magnitude.