Stratocumulus Cloud Field Reflected Fluxes: The Effect of Cloud Shape

Abstract Reflected fluxes are calculated for stratocumulus cloud fields as a function of sky cover, cloud aspect ratio, and cloud shape. Cloud liquid water volume is held invariant as cloud shape is varied so that the results can be utilized more effectively by general circulation models (GCM) and climate models. The magnitude of the reflected flux differences between broken and plane-parallel cloudiness is of particular significance. On the basis of required accuracy in the Earth Radiation Budget Experiment (ERBE) program, an order of magnitude value of 10 W m−2 is used to estimate “significant differences” between plane-parallel and broken cloudiness. This limit is exceeded for cloud covers between 10% and 90%, indicating that plane-parallel calculations are not satisfactory at most values of cloud cover. The choice of cloud shape also leads to large differences in reflected fluxes. These differences may be traced to the anisotropic intensity pattern out the cloud sides, to the size and shape of the “ho...