Simulated effects of internal mixing of anthropogenic aerosols on the aerosol–radiation interaction and global temperature

A partial internal mixing (PIM) treatment of black carbon (BC), organic carbon (OC), and sulphate was examined, and the core-shell model was used to represent the internally mixed aerosols with BC as the core and sulphate or OC as the shell. The influences of PIM treatment on the effective radiative forcing due to aerosol–radiative interaction (ERFari) and global temperature were examined and compared to those of external mixing (EM) treatment using an aerosol-climate online coupled model of BCC_AGCM2.0_CUACE/Aero. Radiative forcing due to aerosol–radiation interaction (RFari) of the anthropogenic aerosols since the preindustrial era was −0.34 W m−2 for EM and −0.23 W m−2 for PIM, respectively. The global annual mean ERFari of anthropogenic aerosols since the preindustrial era was −0.42 W m−2 for EM and −0.34 W m−2 for PIM, respectively. The change in global annual mean surface temperature increased accordingly from −0.18 K in the EM case to −0.125 K in the PIM case. Well geographic consistence between the change in low-level cloud amount and the change in temperature can be found. The atmospheric temperature in the troposphere was markedly less reduced in the PIM case than in the EM case. The RFari/ERFari for 50% and 100% were −0.11/–0.07 and 0.13/0.14 W m−2, respectively. RFari, ERFari, and surface temperature changed approximately linearly with the internal mixing proportion.