| Abstract: |
The purpose of the paper was to develop a numerical model to study the cycle of aerosol particles in stratocumulus clouds in different air mass types. A detailed microphysical scheme was incorporated into an idealized two-dimensional kinematic model to investigate the role of the aerosol particles in the formation of the water droplets, regeneration of the aerosol particles due to evaporation of the water drops, and the washout of the aerosol particles. The calculations were made with different cloud condensation nuclei (CCN) size distributions and concentrations typical for maritime, rural, and remote continental air mass types, furthermore, with two different updraft profiles. The water droplets were formed on soluble ammonium-sulfate aerosol particles. The ratio of the number concentration of the soluble and insoluble aerosol particles depended on their size. The drops grew by condensation and collision coalescence in the updraft core, but they evaporated due to the subsaturation in the downdraft region.
The model clearly simulated the regeneration of the aerosol particles. The majority of the water soluble particles were scavenged due to the water drop formation. The efficiency of the scavenging of the water insoluble particles depended on the concentration of the water soluble aerosol particles. While Brownian effect played an important role in capturing these particles, only few of them were washed out due to the phoretic- and gravitational forces. Results of the numerical simulation show that in the case of the stratocumulus clouds the number concentration of insoluble aerosol particles larger than 0.1 µm is hardly modified due to different scavenging mechanisms. |
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