Effect of Aerosols on the Transfer of Solar Energy Through Realistic Model Atmospheres. Part II: Partly-Absorbing Aerosols

Abstract

Extensive calculations aimed at determining the effect of aerosolson the solar energy absorbed, reflected and transmitted by cloudless,nonhomogeneous, plane-parallel atmospheric models were recently carriedout with the object of treating the radiation transfer in as comprehensivea manner as possible consistent with reasonable computing time. Theconcentration of aerosol (spherical particles with size distributionand refractive index independent of height), ozone and water vaporwere specified for 160 layers of varying thickness from the surfaceto 45 km. The solar spectrum (0.285?2.5 ?m) was divided into 83 intervalswith appropriate functions representing the scattering and absorptionof gases and aerosol assigned to each, the index of refraction ofthe aerosol taken to be wavelength-independent. Upward and downwardfluxes for each spectral interval at each level were computed takinginto account all orders of scattering. Results will be presentedfor four model atmospheres to show the absorbed, diffusely reflected,and diffusely as well as directly transmitted (spectrally integrated)solar flux for a range of Lambert ground reflectivities and solarzenith angles. The first model (A) is free of aerosols and absorbinggases. The remaining models contain carbon dioxide, ozone and watervapor representative of average summer mid-latitude conditions. ModelB contains no aerosol; Model C contains an aerosol distribution typicalof average clear sky conditions; and Model D has increased aerosolconcentration near the ground and in the Junge layer located in thelower stratosphere.