Chemical characteristics of the aerosols and their effect on microphysical properties of clouds in spring and summer over Mt. Huang

The aerosol components and cloud microphysical parameters were measured at a high altitude background station on the summit of the Mt. Huang from May to August 2009, and were used as input to a multi chemical component (MCC) binresolved cloud parcel model to investigate the influence of MCC aerosols on the cloud condensation nuclei (CCN) and cloud microphysics. The results from the back trajectory cluster and aerosol ionic composition analysis show that there were three types of air masses that affected the chemical composition of the aerosol particles, including the northern continental, local polluted, and mixed transformation maritime air mass, with characteristic substance of CaCO3, soluble salts ((NH4) 2SO4, NH4NO3), as well as NaCl, respectively. The numerical simulation results show that the effects of aerosol chemical compositions on cloud microphysical processes varied with weather conditions for the same aerosol distribution. MCC aerosols led to higher cloud droplet number concentration (CDNC) than pure ammonium sulfate aerosols under the same updraft velocity, mainly reflected in more droplets with sizes less than 3.3 μm. It is also shown that inclusion of the insoluble component CaCO3 has more significant influence on the CDNC when the updraft velocity is lower than 0.7 m/s; otherwise, NaCl dominated the droplet activation process with the increasing condensable water. The MCC aerosols resulted in relatively narrow cloud droplet spectrum than pure ammonium sulfate aerosols, especially when the area is influenced by the northern continental air mass. In the latter case, MCC aerosols led to enhanced the cloud droplet number, cloud optical thickness and cloud albedo, and decreased the droplet effective radius, and therefore, may have different effects to warm precipitation and atmospheric radiation compared with other types of air masses.