A hybrid cloud regime methodology used to evaluate Southern Ocean cloud and shortwave radiation errors in ACCESS

Shannon Mason, Jennifer K Fletcher, John M Haynes, Charmaine Franklin, Alain Protat, Christian Jakob

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15 Citations (Scopus)

Abstract

A deficit of shortwave cloud forcing over the Southern Ocean is persistent in many global climate models. Cloud regimes have been widely used in model evaluation studies to make a process-oriented diagnosis of cloud parameterization errors, but cloud regimes have some limitations in resolving both observed and simulated cloud behavior. A hybrid methodology is developed for identifying cloud regimes from observed and simulated cloud simultaneously. Through this methodology, 11 hybrid cloud regimes are identified in the ACCESS1.3 model for the high-latitude Southern Ocean. The hybrid cloud regimes resolve the features of observed cloud and characterize cloud errors in the model. The simulated properties of the hybrid cloud regimes, and their occurrence over the Southern Ocean and in the context of extratropical cyclones, are evaluated, and their contributions to the shortwave radiation errors are quantified. Three errors are identified: an overall deficit of cloud fraction, a tendency toward optically thin low andmidtopped cloud, and an absence of a shallow frontal-type cloud at high latitudes and in the warmfronts of extratropical cyclones. To demonstrate the utility of the hybrid cloud regimes for the evaluation of changes to the model, the effects of selected changes to the model microphysics are investigated.
Original languageEnglish
Pages (from-to)6001-6018
Number of pages18
JournalJournal of Climate
Volume28
Issue number15
DOIs
Publication statusPublished - 2015

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