Abstract
A superimposed sinusoidal model is proposed to investigate the effects of cloud dimension and geometrical fine structure on the light scattering of cumulus clouds in the visible region.
For various cloud shapes, cloud dimension, and solar zenith angle, efficiency of shadowing and conversion from directional light to diffused light, albedo, upwelling reflectance, the horizontal pattern of scattering, and upwelling radiance are calculated by using the Monte Carlo method. Finite small perturbation on the upper cloud surface is found to be an important factor which governs the mean and the variance of radiative properties of clouds. The mean albedo of cumuliform cloud field is lower than that of the conventional cuboidal model due to the asymmetry of cloud shape. Therefore, neither the right parallelpiped cloud model nor simple sinusoidal one is a representative of the radiative properties of cloud group with various shapes. The variance of cumulus radiative properties are so large that the relation between cloud dimension and radiance is valid only for a statistical number of clouds in estimating liquid water content.
