BROKEN CLOUD OBSERVATIONS AND PARAMETERIZATIONS FOR LONGWAVE RADIATION

Clouds play a major role in regulating Earth s climate. However, computer models of Earth s climate include cloud effects in a primitive manner by assuming clouds to be flat the flat plate approximation. Cumulus clouds behave differently from flat plates because the vertical extent of the clouds shades more of the atmosphere and allow radiative exchange over a larger temperature range. To overcome the simplicity of GCMs but not to add too much computation, the effective cloud fraction is considered as a practical way to improve the plane-parallel theory. In this study, we use experimental data from a cloud radar, a lidar, and other observations to extract cloud information (coverage, thickness and aspect ratio) with which to test Ellingson s random cloud model. The extracted data are compared for consistency, and are used with radiation flux data to interpret the ability of the different techniques to infer cloud properties which are important to longwave radiative transfer under broken cloud conditions. 1