Chemical Species Contributions to Light Scattering by Aerosols at a Remote Arid Site Comparison of Statistical and Theoretical Results

Abstract

A one-year, aerosol-light extinction experiment was conducted at China Lake, California, an arid site in the Mohave Desert. Measurements of the aerosol size distribution, the light scattering coefficient, and fine aerosol chemical composition were made. Multiple regression analysis was applied to the measured particle light scattering coefficient and fine aerosol species mass concentrations from 61 filter samples collected during 1979. Contributions of various aerosol species to the particle light scattering coefficient, b_(sp), were estimated. The statistically estimated contributions were compared with those determined theoretically using measured aerosol mass distributions. It was found that the statistically inferred species contributions to b_(sp) agreed qualitatively with those calculated theoretically using measured aerosol distributions. Regression analysis overestimated the contribution of sulfate relative to that calculated theoretically. Using measured 1979 values, a light extinction budget was calculated for China Lake. Measured mass extinction coefficients were used to predict the reduction in visibility at China Lake which would occur by increasing the concentrations of various aerosol species.

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