The influence of clouds on radiation: A climate‐modeling perspective

The influence of clouds on the radiation field is reviewed from the point of view of their representation in climate models. Such models are expected to include, in the very near future, condensed water as an additional prognostic variable. We examine how simple parameterizations based on the liquid water content can realistically simulate the radiation field. We focus on the extended low‐level clouds for which numerous results of simultaneous radiation and microphysics measurements are available. Particular attention is given to the shortwave absorption in cloud layers because theoretically calculated absorptances are generally weaker than those observed. The problem of the broken field is approached in terms of a relationship between the actual cloud cover and the equivalent cloud cover which gives the same irradiances but using the plane‐parallel formalism.