The air quality model system RAMS (Regional Atmospheric Modeling System)-CMAQ (Models-3 Community Multi-scale Air Quality) coupled with an aerosol optical/radiative module was applied to investigate the impact of different aerosol mixing states (i.e., externally mixed, half externally and half internally mixed, and internally mixed) on radiative forcing in East Asia. The simulation results show that the aerosol optical depth (AOD) generally increased when the aerosol mixing state changed from externally mixed to internally mixed, while the single scattering albedo (SSA) decreased. Therefore, the scattering and absorption properties of aerosols can be significantly affected by the change of aerosol mixing states. Comparison of simulated and observed SSAs at five AERONET (Aerosol Robotic Network) sites suggests that SSA could be better estimated by considering aerosol particles to be internally mixed. Model analysis indicates that the impact of aerosol mixing state upon aerosol direct radiative forcing (DRF) is complex. Generally, the cooling effect of aerosols over East Asia are enhanced in the northern part of East Asia (Northern China, Korean peninsula, and the surrounding area of Japan) and are reduced in the southern part of East Asia (Sichuan Basin and Southeast China) by internal mixing process, and the variation range can reach ±5 W m-2 . The analysis shows that the internal mixing between inorganic salt and dust is likely the main reason that the cooling effect strengthens. Conversely, the internal mixture of anthropogenic aerosols, including sulfate, nitrate, ammonium, black carbon, and organic carbon, could obviously weaken the cooling effect.
The structure of atmospheric boundary layer determines the ability of atmospheric dispersion and has an essential impact on airborne aerosols.In this paper,the data of a radio sounding experiment held in Dongguan National Meteorological Observation Station,which is in a coastal city in Pearl River Delta,as well as the data of atmospheric aerosols,were utilized in order to analyze the characteristics of atmospheric boundary layer and its effects on surface aerosol concentrations.The results are showed at follows:the local circulations,associated with dominant winds,made complex structures of atmospheric layers,as the cold air and systematic winds weakened in the end of a cold air event.Weakened wind shears and inversion layers,especially a strong near-surface inversion layer,remarkably diminished the atmospheric diffusion abilities and facilitated an especially high concentration of surface aerosols.The convergence line or weak shear line of sea breeze in the ground level helps weaken the atmospheric diffusion abilities and results in atmospheric aerosols accumulation.
