The Effective Radiative Forcing of Partial Internally and Externally Mixed Aerosols and Their Effects on Global Climate

The total effective radiative forcing (ERF) due to partial internally mixed (PIM) and externally mixed (EM) anthropogenic aerosols, as well as their climatic effects since the year of 1850, were evaluated and compared using the aerosol–climate online coupled model of BCC_AGCM2.0_CUACE/Aero. The influences of internal mixing (IM) on aerosol hygroscopicity parameter, optical properties, and concentration were considered. Generally, IM could markedly weaken the negative ERF and cooling effects of anthropogenic aerosols. The global annual mean ERF of EM anthropogenic aerosols from 1850 to 2010 was -1.87 W m^–2, of which the aerosol-radiation interactive ERF (ERF_ari) and aerosol-cloud interactive ERF (ERF_aci) were -0.49 and -1.38 W m⁻², respectively. The global annual mean ERF due to PIM anthropogenic aerosols from 1850 to 2010 was -1.23 W m^–2, with ERF_ari and ERF_aci of -0.23 and -1.01 W m⁻², respectively. The global annual mean surface temperature and water evaporation and precipitation were reduced by 1.74 K and 0.14 mm day^–1 for EM scheme, and 1.28 K and 0.11 mm day^–1 for PIM scheme, respectively. However, the relative humidity near the surface was slightly increased for both mixing cases. The intertropical convergence zone (ITCZ) was southwardly shifted for both EM and PIM cases, but was less southwardly shifted in PIM scheme due to the less reduction in atmospheric temperature in the mid and low latitudes of the Northern Hemisphere.