ABSORPTION OF SOLAR-RADIATION BY CLOUDS - OBSERVATIONS VERSUS MODELS

There has been a long history of unexplained anomalous absorption of s olar radiation by clouds. Collocated satellite and surface measurement s of solar radiation at five geographically diverse locations showed s ignificant solar absorption by clouds, resulting in about 25 watts per square meter more global-mean absorption by the cloudy atmosphere tha n predicted by theoretical models. It has often been suggested that tr opospheric aerosols could increase cloud absorption. But these aerosol s are temporally and spatially heterogeneous, whereas the observed clo ud absorption is remarkably invariant with respect to season and locat ion. Although its physical cause is unknown, enhanced cloud absorption substantially alters our understanding of the atmosphere's energy bud get.