Radiative Transfer in Nonhomogeneous Cirrus Clouds: Application to Remote Sensing

Abstract

From lidar measurements of cirrus clouds, it has been illustrated that the backscattering coefficients vary significantly in space as constructed from the time series of backscattering returns (Sassen 1990; Spinhirne and Hart 1990). A complete understanding of the radiative properties of cirrus clouds and their parameterizations would require specific investigation of the potential effects of cloud spatial inhomogeneity on the transfer of radiation. In this paper, we have developed a three-dimensional, nonhomogeneous radiative transfer model based on the successive orders of scattering approach coupled with discretization of the radiation field in spatial and angular coordinates. Using the retrieved optical depth from AVHRR high-resolution data (≈ 1×1 km2) (Ou et al. 1993; Rao et al. 1994) and the observed ice crystal size distribution information from balloon-borne replicators (Ou et al. 1994), we investigate the effect of spatial inhomogeneity on the reflected and transmitted solar radiances and fluxes for cirrus clouds.