Understanding Cloud Radiative Effects via Different Cloud Classifications

The role of clouds in the planet’s energy flows is widely accepted to be formidable. In this presentation, we will discuss two approaches to decompose the effects of clouds on the Earth’s radiation budget, expressed in terms of the Cloud Radiative Effect (CRE). One approach relies on passive observations for cloud classification (Cloud Regimes derived from MODIS, CR), while the other relies on active observations (Cloud Vertical Structure classes derived from CloudSat and CALIPSO, CVS). The analysis reveals aspects of cloud characteristics that make them either radiative warmers or coolers from the perspective of the planet as a whole, the surface, and the atmosphere. The degree of radiative warming or cooling depends on the magnitude of the combined shortwave and longwave CRE. We find that all CRs cool the planet as a whole and the surface; those dominated by high clouds warm the atmosphere and those by low clouds cool it. When using cloud vertical configuration as the criterion of cloud decomposition, only two of ten CVS classes, both comprising high clouds are found to be radiative warmers of the planet and six to be radiative warmers of the atmosphere. All CVS classes, on the other hand, cool the surface. The ultimate global radiative importance of the various CRs and CVS classes depends critically on their global occurrence frequency: the most prominent contributors to the TOA, surface and atmospheric global CRE will be identified.