Development of mixed-phase clouds from multiple aerosol size distributions and the effect of the clouds on aerosol removal

[1] This paper provides numerics for cloud and precipitation development from multiple aerosol size distributions and examines the effect of clouds and precipitation on aerosol removal. Numerical techniques are given for (1) simultaneous liquid and ice growth onto multiple aerosol size distributions, (2) diffusiophoretic, thermophoretic, gravitational, etc., coagulation among liquid, ice, and graupel, and their aerosol components, (3) contact freezing (CF) of drops by size-resolved interstitial aerosols, (4) heterogeneous plus homogeneous freezing, (5) liquid drop breakup, (6) coagulation of cloud hydrometeors and incorporated aerosols with interstitial aerosols, (7) coagulation of precipitation hydrometeors with interstitial and below-cloud aerosols (washout), (8) removal of precipitation and incorporated aerosols (rainout), (9) below-cloud evaporation/sublimation to smaller hydrometeors and aerosol cores, (10) gas washout, and (11) aqueous chemistry. Major conclusions are (1) hydrometeor-hydrometeor coagulation appears to play a substantial role in controlling aerosol-particle number globally, (2) washout (aerosolhydrometeor coagulation) may be a more important in-plus below-cloud removal mechanism of aerosol number than rainout (the opposite is true for aerosol mass), (3) close-in diameter dual peaks in observed cloud distributions may be in part due to different activation characteristics of different aerosol distributions, (4) evaporative cooling at liquid drop surfaces in subsaturated air may be a mechanism of drop freezing (termed ‘‘evaporative freezing’’ here), and (5) heterogeneous-homogeneous freezing may freeze more upper-tropospheric drops than CF, but neither appears to affect warm-cloud hydrometeor distributions or aerosol scavenging substantially.