Liquid Water Content of Fogs and Hazes from Visible Light Scattering

Abstract

A new method is proposed for measuring the liquid water content of fogs and hazes. It consists of a planar circular light sensor placed perpendicular to and coaxial with a narrow collimated light beam of a visible wavelength. The direct light from the beam, which is narrower than the width of the sensor, is blocked near the sensor, so that the sensor sees only the light scattered in the near-forward direction by the droplets in the beam. Calculations with numerous droplet size distributions found in maritime fog, and haze aerosols show that the flux of scattered light is approximately proportional to the liquid water content. Advantages of an instrument using the proposed method would be in situ measurements, rapid response, compactness and simplicity.