The Chemical Characteristics Of Aerosol And Their Effect On Microphysical Properties Of Clouds At Mt. Huang

Recent studies showed that, the aerosol size spectra, chemical composition and mixed state will have an impact on the cloud microphysical characteristics. The aerosol components and cloud microphysical parameters were measured at a high-altitude background station on the summit of Mt. Huang from June to July2011, and were used as input to a multi-chemical-component (MCC) bin-resolved cloud parcel model to investigate the influence of MCC aerosols on hygroscopic growth, CCN and cloud microphysics.During the observation period, aerosol mass concentration at Mt. Huang will increase rapidly with high temperature, low wind and no effective precipitation. The aerosol water-soluble ion accounts for34.2%of the total mass concentration. The average SO42-anion concentration (12.3μg/m3) is the highest, followed by NO3-(2.9μg/m3). The average cation concentration is Ca2+and NH4+were2.1μg/m3and1.8μg/m3respectively. Organic acid accounts for11.37%of the water-soluble composition. The results from back trajectory cluster and aerosol ionic composition analysis show that three types of air masses affected the chemical composition of aerosol particles, including the northern continental (35%), local polluted (47%), and southwest air mass (18%). The highest aerosol mass concentration (21μg/m3) caused by local pollution, which is closely related to the low voltage system, the lower surface wind speed and other meteorological factor.Based on the actual observation data, the initial aerosol spectrum in the model is measured by WPS in the same period. Numerical simulation results show that the hygroscopic properties of MCC aerosol at Mt. Huang varied with the air mass. The hygroscopic growth factor of mixed aerosol is highest (Gf=1.98, RH=90%), followed by urban aerosol (Gf=1.95, RH=90%) and inclusion of insoluble component CaCO3caused by the northern continental air mass (Gf=1.91, RH=90%).Under different saturation simulated values and observed values are affected by weather conditions. When super saturation is lower, the CCN value simulated is higher than the sunny and rainy days observing CCN value, below the fog CCN observations. When super saturation is greater than0.6%, the CCN value simulated by MCC aerosol is about sunny days observation value of3times, and similar to observations in the fog.Numerical simulation results show that the effects of aerosol chemical compositions on cloud microphysical processes varied with weather conditions for the same aerosol distribution. Order of magnitude of the CDNC observation and simulated by the MCC aerosol are in the102个/cm3. It is also shown that inclusion of insoluble component CaCO3has more significant influence on CDNC when the updraft velocity is lower than0.7m/s; otherwise, NaCl dominated droplet activation process with increased condensable water. MCC aerosols led to higher cloud droplet number concentration (CDNC) than pure ammonium-sulfate aerosols under the same updraft velocity mainly represented as more droplets with sizes less than3.0μm. The MCC aerosols resulted in relatively narrow cloud droplet spectrum, especial in the northern continental air mass case (max droplet radius9.92μm), than pure ammonium-sulfate aerosols(max radius10.3μm). Compared with the observed values, the simulation of particle in4-5μm size is with the same order of magnitude.