Microwave Measurements of the Liquid Water Content of Atmospheric Aerosols

Abstract

A new method is described for the measurement of the dielectric constant of atmospheric aerosols. From these observations the free liquid water content of airborne particles can be deduced. An instrument to measure semi-continuously the dielectric constant of aerosols is discussed, and illustrative observations are given for urban air in Southern California and for marine and desert air at non-urban sites. The results taken during the fall of 1972 indicate that a significant fraction of the marine and urban aerosol observed is free water in the relative humidity range between 40 and 75%. The liquid water content in the aerosol correlates satisfactorily with the extinction coefficient for visible light, as measured with an integrating nephelometer.