Evaluating Mean State Cloud Properties in the Simple Cloud-Resolving E3SM Atmosphere Model

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Li-Wei Chao, Mark D. Zelinka, Christopher Ryutaro Terai, Hassan Beydoun, Benjamin R Hillman, Noel D. Keen, Peter Martin Caldwell, Stephen A. Klein

Published: 31 Jul 2025, Last Modified: 05 May 2026CrossrefEveryoneRevisionsCC BY-SA 4.0
Abstract: Accurately simulating clouds remains a key challenge in global climate models, primarily because cloud formation involves sub-grid processes that are parameterized and crudely represented in models. This study examines the performance of DOE’s Simple Cloud-Resolving Energy Exascale Earth System (E3SM) Atmosphere Model (SCREAM) in simulating cloud properties and their spatio-temporal distribution by comparing against satellite observations. Two horizontal resolutions of SCREAM (3 and 12km) are examined, and both depict a realistic spatial structure of mean-state cloud cover but underestimate its global mean magnitude. SCREAM 3km faithfully reproduces the distribution of mean-state cloud properties across various cloud optical thickness and cloud-top pressure regimes, with an error that is smaller than that of the 12km and most CMIP5 and CMIP6 models. Still, SCREAM tends to underpredict low clouds and optically thin clouds, highlighting the need for continued improvement in representing unresolved processes. This study provides a basis for confidence in the representation of clouds in SCREAM, as simulating mean-state clouds is a necessary prerequisite for trusting its cloud responses to changes in aerosols and greenhouse gases.