Two-Dimensional Simulation of the Thermal Environment of a Polluted Urban Atmosphere: Effects of Aerosol Characteristics

A two-dimensional numerical simulation is carried out for the unsteady heat transfer in a polluted urban boundary layer containing aerosols. The effects of aerosols upon the thermal structure over a region including an urban area are studied synthetically in full consideration of radiative heat transfer. The results indicate a strong interaction among the distribution of air temperature, wind velocity and aerosol concentration in connection with the scattering and absorbing characteristics of aerosols. When the scattering of solar radiation by aerosols is predominant, the air temperature in the urban area drops greatly, and the convergent flow to the urban area becomes weak, causing the aerosol concentration in the urban area to become high when the absorption of solar radiation is predominant, the convergent flow to the urban area is not weakened. Air temperature drops near the earth surface, but the change in the upper air temperature is small.