Treatments of Inhomogeneous Clouds in a GCM Column Radiation Model

The main purpose of this abstract is to evaluate the performance under inhomogeneous cloud conditions of the Column Radiation Models (CORAMs) developed by Chou and collaborators (see references), and used in various NASA-Goddard General Circulation Models (GCMs). Testing more sophisticated research versions of the CORAM that account for cloud inhomogeneity is secondary, and relevant findings will be shown only for the shortwave (SW) CORAM (we note however that algorithms that take into account the inhomogeneous nature of clouds at the infrared part of the spectrum have also been developed, see Li and Barker 2002). The CORAMs are evaluated on global scales, but with the caveat that the input cloud data come from only one of 500 simulated days. Still, this is an improvement over previous studies where assessments of the errors of this type of plane-parallel homogeneous (PPH) codes were made using a limited number of cloud fields generated either by theoretical models (e.g., Cahalan et al. 1994) or by Cloud Resolving Models (CRMs) attempting to simulate the clouds of a specific field campaign (e.g., Barker et al. 1999).

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