The cloud radiative effects of International Satellite Cloud Climatology Project weather states

Abstract

The salient features of the daytime cloud radiative effect (CRE, also known as cloud radiative forcing) corresponding to various cloud regimes or weather states are examined. The analysis is based on a 24 year long data set from the International Satellite Cloud Climatology Project (ISCCP) for three distinct geographical zones covering most of the Earth's surface area. Conditional sampling and averaging of the ISCCP cloud fraction and CRE in 2.5 grid cells is performed for each weather state, and the state's radiative importance expressed as the relative contribution to the total CRE of its geographical zone is explained in terms of dominant cloud type, cloud fraction, and frequency of occurrence. Similarities and differences within and between geographical zones in the cloud fraction and CRE characteristics of the various weather states are identified and highlighted. By providing an exposition of the radiative energy characteristics of different cloud type mixtures, we facilitate the meteorological situation-dependent evaluation of radiation budget effects due to clouds in climate models. Copyright 2011 by the American Geophysical Union.