VISIBILITY AND LIQUID WATER CONTENT IN THE FREE ATMOSPHERE

Abstract

Koschmieder's formula is verified by experimental data obtained on Mt. Washington and is used to determine visibility in clouds from measurements of the scattering coefficient. Visibility in clouds varies from approximately ten meters in large cumulus clouds to several hundred meters in stratus-like clouds. Knowing the visibility, it is possible to calculate the liquid water content by applying the Trabert formula if, in addition, the drop-size is known. The droplets are photomicrographed by the Hagemann and Diem method. The average droplet radius is about 4µ in fair weather cumulus and stratocumulus, about 7µ in stratus-like clouds and about 10µ in cumulus congestus. The average water content in large cumulus clouds is approximately 2.5 g/m3 in fair weather cumulus 0.5 g/m3 and in stratus 0.2 g/m3.