Effects of industrial pollution on cumulus convection and rain showers: A numerical study

A numerical cloud model with bulk-water microphysics is used to stimulate a cumulus developing in the polluted plume emitted from a large industrial plant. The pollution effects are included in the model by adjusting the cloud droplet concentration, the mass dispersion of the cloud droplet spectrum and the supersaturation value required for cloud condensation. The cloud dimensions and updraft magnitudes of the simulated cumulus agree well with observations. Sensitivity experiments reveal that the pollution has only a minor effect on the cumulus development 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 Method these increases in rainfall can be attributed mainly to the mutual interaction of the supersaturation and the drop spectrum effects, while the individual contributions are very small.