RADIATION TRANSFER IN FINITE CYLINDRICAL CLOUDS

An analytical method is developed for determining radiation transport in finite cylindrical clouds. The cylindrical form is taken as the ide alized shape of cumulus clouds. In the shortwave part of the spectrum illumination by the direct solar beam is considered. In the infrared t he cloud's emission as well as the radiation emitted by an underlying ground is taken into account. Numerical computations are carried out t o illustrate the applicability of the technique developed in the prese nt study. For a cloud in an absorbing midlatitude summer atmosphere re sults are shown for the shortwave region including spectral integratio n. Cloud transmission and albedo are presented as a function of solar zenith angle and as a function of the cloud's dimensions. The results are in agreement with published results from Monte Carlo calculations as far as a comparison is possible. Vertical profiles of the solar hea ting rate in the cylindrical cloud indicate the effect of the cloud's finite dimensions. Similarity as well as differences are found from co mparison with results obtained for a cuboidal cloud from a finite anal ytical model that was tested successfully against Monte Carlo calculat ions.