EFFECTS OF INDUSTRIAL-POLLUTION ON CUMULUS CONVECTION AND RAIN SHOWERS - A NUMERICAL STUDY

A numerical cloud model with bulk-water. microphysics is used to stimu late a cumulus developing in the polluted plume emitted from a large i ndustrial plant. The pollution effects are included in the model by ad justing the cloud droplet concentration, the mass dispersion of the cl oud droplet spectrum and the supersaturation value required for cloud condensation. The cloud dimensions and updraft magnitudes of the simul ated cumulus agree well with observations. Sensitivity experiments rev eal that the pollution has only a minor effect on the cumulus developm ent and the rainfall. Heavy pollution conditions cause an increase of accumulated rainfall by 1.8%, whereas light pollution indicate an even smaller rainfall enhancement of 0.2%. Using the Factor Separation Met hod these increases in rainfall can be attributed mainly to the mutual interaction of the supersaturation and the drop spectrum effects, whi le the individual contributions are very small.