Using Eppley pyrheliometers mounted on a blimp, observations were made of the upward and downward flux of short-wave radiation above, in, and below coastal stratus throughout the summer of 1945. These observations are summarized and evaluated in terms of the percentage of the incident radiation reflected, absorbed, and transmitted, as a function of the thickness of the cloud.
The simplified radiative transfer equations, in which the radiation is considered to be composed of upward and downward isotropic currents, are solved for general distributions of drop size and liquid-water content, and applied to the distributions found in coastal stratus. The theoretical variation with cloud thickness differs from the observed. This is taken to indicate that the simplified theory is an inadequate description because the radiation is not isotropic.