Effect of Diffusion-Sedimentation and Washout Processes on Aerosol Size Distributions

[摘要] It is studied how the size distribution of the so-called giant aerosols is changed by the diffusion-sedimentation and washout in the atmospheric boundary layer. An instantaneous and a continuous sources of infinite horizontal extent are assumed for ejection of aerosols into the atmosphere. The size distribution are calculated numerically as a function of time and height above ground for various combinations cf the eddy diffusivity profile and the rainfall intensity. The computational results are as follows. (1) The size distribution changes with time or height in such a way that the concentration of particles decreases with increase of particle size. (2) The effect of the diffusion-sedimentation simply reflects on the deforma-tion of the size distribution of larger particles. (3) The degree of deformation of the size distribution by the washout increases with increase of particle size in the case of instantaneous source, and it is most pronounced for intermediate particle size range when the time duration of particle emission is sufficiently long.

[学科分类] 大气科学