A Theoretical Investigation of the Effect of Aerosol Pollutants on Shortwave Flux Divergence in the Lower Troposphere

Abstract

This study is aimed at evaluating shortwave effects of aerosol pollutants in the lower troposphere (surface to 2 km). We have solved the radiative transfer equation for a plane-parallel atmosphere of infinite extent in the horizontal but inhomogeneous and of finite extent in the vertical. The vertical inhomogeneity is due to the presence of a non-uniform aerosol distribution, and a non-uniform concentration distribution of absorbing gases. The shortwave spectrum is divided into a sufficient number of intervals to simulate absorption characteristics of various atmospheric gases. The equation of radiative transfer is solved for these spectral intervals taking into account all orders of scattering. Simulations have been made, using several representative vertical distributions of aerosols, typical aerosol values of refractive indices, and various size distribution functions. The analyses of these results indicate that the spectrally integrated flux divergence in the lower troposphere is highly dependent on solar zenith angle, the imaginary part of the refractive index, and the height and size distributions of the aerosol. The effect of gaseous absorption, however, has a smaller influence on the flux divergence.