Two-dimensional numerical simulation of the effects of air pollution upon the urban-rural complex

A two-dimensional radiative-dynamic interaction model is developed to study the impact of air pollution on urban areas and on the regions directly downwind of the city. By isolating component effects, such as variable soil parameters and roughness heights, it becomes possible to comprehend the behavior of the complete model.

The model includes low and elevated pollution as well as artificial urban heat sources. Geostrophic winds of 2 and 5 m/s are used to model the wind field, vertical motion is included. Stability effects on vertical mixing are accounted for in terms of the similarity theory.

The radiative treatment is based on the exact formulation of the radiative transfer equation which accounts for multiple scattering of aerosol particles in the solar spectrum as well as in the water vapor window. In addition to the radiative effects of water vapor and carbon dioxide, the presence of NO2 is accounted for.

It is found that an artificial heat source causes surface heating of 4°C, while urban soils lead to lower surface temperatures up to 4°C during the day and warmer temperatures up to 3°C during the night. The effect of increased roughness is an increased temperature up to 4°C at shelter height during the day and a decreased temperature of 2.5°C during the night. Low-level pollution sources lead to 2°C surface temperature decreases during the day, while upper level sources may lead to decreases of 7°C under stagnant conditions in urban areas.