Solar Radiative Transfer in Clouds with Vertical Internal Inhomogeneity

Abstract

To investigate the photon transport in inhomogeneous clouds, a MonteCarlo cloud model with intemal variation of optical properties isdeveloped. Tbc data for cloud vertical internal inhomogeneity arechosen from published observations. Paranieterization of the solarradiative properties of clouds is used in the forrn of the liquidwater content and the effective radius of cloud droplet. The MonteCarlo simulations show that for overcast stratocumulus clouds, thedifferences in reflectance between the vertical inhomogencous cloudsand their planeparallel counterpart are very small (only about M).Ilese differences can be enhanced up to 10% for large solar zenithangles, when the overcast clouds are separated into broken cloudfields. lf the cloud coverage is large, the vertical inhomogeneityof clouds can cause about I% increase in cloud absorption, whichmay help to explain the cloud absorption anomaly. Also, the parameterizationof effective cloud amount for cloud absorption is discussed.