Numerical Simulations of Cloud Condensation Processes


Abstract:Clouds are collections of tiny particles of water and/or ice that are large enough to be visible. Thetwo required ingredients for the formation of cloud are water vapor and aerosols. The spontaneous growthof Cloud Condensation Nuclei (CCN) into cloud droplets under supersaturated water vapor conditionsis described by classic Köhler theory. The aim of this work is to model Köhler theory and investigateeffects of mass, solubility, and composition of the CCN in the formation and growth of cloud droplets.Sodium Chloride (NaCl) and Ammonium Sulfate ((NH4)2SO4) were used as a solute material. The resultsshowed that both mass and solute material affect the nucleation of cloud droplet. Increasing mass of solutewould increase the critical radius and decrease the supersaturation required for activating the droplet. Itwas found that the use of NaCl produce critical radius larger than that of (NH4)2SO4 and the requiredsupersaturation for NaCl solute is lower than that of (NH4)2SO4 solute. This is due the fact that NaCl haslower molecular weight than (NH4)2SO4. The results also indicate that cloud temperature has minor effecton the cloud droplet activation. The model can be used to investigate more suitable solute materials todetermine which is best for cloud seeding projects.