Numerical Modeling Of Aerosols Effects On Warm Cloud

Based on the cloud scheme of Chinese Academy of Meteorological Sciences(CAMS), awarm cloud model with prognostic variables of concentrations of aerosols,CCN and clouddrops was developed.Firstly ,we discussed the effects of different initial aerosol particles spectra on warm cloud.Then the effects of gain nuclei on warm cloud was studied and compared the effects of cloudaerosol distribution to that of maritime aerosol distribution on envolution of warm cloud.Coupled with observed data on aerosols of Beijing, we studied the effects of different aerosoldistribution of Beijing on CCN, cloud drops and cloud water content. The simulated resultswere compared with observation. Shows the results as follow:(1) There is significant difference between the effects of continental aerosol distribution andthat of maritime aerosol distribution on CCN, cloud drops and cloud water content. TheCCN concentration of continental cloud is higher than the CCN concentration of maritimecloud. At 0.5 km from ground ,the total CCN concentration of maritime cloud is about1.0×102 /cm3 while that of continental cloud is about 1.0×103/cm3 ,when thesupersaturation is 1.0%. The cloud drops concentration of continental cloud is higher thanthat of maritime cloud. Therefore the cloud drops of continental cloud are smaller thanthat of maritime cloud. In general, the maritime aerosol distribution enhances thedevelopment of precipitation compared with continental aerosol distribution.(2) There is significant difference between the effects of different continental aerosoldistribution on warm cloud. We could find a significant effect on CCN concentrationwhen the aerosol distribution is different. The CCN concentration was high when theconcentration of aerosol ( r > 1.0μm) is increased. But increasing the concentration ofaerosol ( r < 1.0μm) has minor effects on the CCN concentration and cloud dropconcentration. In general, different continental aerosol distribution has minor effects oncloud water content. The sensitivity simulation shows that the reduction of precipitationdue to the increases of aerosols( 0. 1μm < r<1.0μm) concentration because increasingthe CCN concentration and cloud drop concentration have negative effects on the onset ofcollision coalescence.(3) The presence of giant nuclei ( r > 1.0μm) is only important in the initial stages of cloudenvolution. It was found that giant nuclei enhance the envolution of precipitation due tothe increasing of large cloud drop concentration suppress the onset of collisioncoalescence in the initial stages of cloud envolution. No significant effects on precipitationin the subsequent stage.