Modeling of growth and evaporation effects on the extinction of 1.0-microm solar radiation traversing stratospheric sulfuric acid aerosols.

In earlier papers we presented results of parametric studies of the separate and combined effects of aerosol microphysical processes on the time dependence of extinction of four visible and IR laser beams traversing an aerosol medium. Results of these studies can be applied to monitor the temporal changes of aerosol properties inside a cloud chamber or in an open environment in the troposphere. As a continuation of this series, the effects of growth and evaporation of sulfuric acid aerosols in the stratosphere on the extinction of solar radiation traversing such an aerosol medium are reported in this paper. Extinction of 1.0-microm solar radiation was studied since this wavelength was used to monitor the aerosol extinction properties by two recent satellite experiments: Stratospheric Aerosol Measurement II (SAM II) and Stratospheric Aerosol and Gas Experiment (SAGE). Our modeling results show that aerosol extinction is not very sensitive to the change of ambient water vapor concentration but is sensitive to the change of ambient temperature, especially at low ambient temperature and high ambient water vapor concentration. The effects of initial aerosol size distribution and composition on the change of aerosol extinction due to growth and evaporation processes are elucidated. The application of results of this parametric study is discussed.