Exposing and Reducing Biases of Simulating Mixed-Phase Clouds in the Convection-Permitting E3SM Atmosphere Model: Lessons From an Arctic Cold-Air Outbreak

Journal Article · Fri Jan 30 00:00:00 EST 2026 · Journal of Geophysical Research. Atmospheres

DOI:https://doi.org/10.1029/2025JD044660· OSTI ID:3018095

Lin, Lin ^[1]; Zhang, Yunyan ^[1]; Beydoun, Hassan ^[1]; Zheng, Xue ^[1]; Zhang, Meng ^[2]; Bogenschutz, Peter ^[1]; Wu, Peng ^[3]; Caldwell, Peter M. ^[1]

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1. Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
2. Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Univ. of Houston, TX (United States)
3. Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

Mixed-phase clouds modulate the water and energy cycles of high-latitude regions, yet their liquid-ice phase partitioning has long been poorly simulated in climate models. Here, simulations of Arctic mixed-phase clouds by the Simple Cloud-Resolving E3SM Atmosphere Model (SCREAM) are assessed against large-eddy simulations, satellite data, and ground-based observations during the Cold-Air Outbreaks in the Marine Boundary Layer Experiment field campaign. SCREAM simulates nearly completely frozen clouds, which is attributed largely to the unreasonably strong Wegener–Bergeron–Findeisen (WBF) process that converts liquid to ice excessively and partly to the early over-abundant ice production at cold temperatures from a temperature-deterministic deposition ice nucleation scheme. Assuming no subgrid variation for the WBF process in the original formulation particularly conflicts with the instantaneous saturation adjustment assumption in the condensation scheme that assumes subgrid variability, leading to exaggerated WBF process rates. A proposed simple physically-based improvement on the treatment of subgrid cloud overlap substantially increases supercooled liquid water content and notably improves cloud-top phase partitioning, aligning better with observations. Improvement of supercooled liquid water content also converges with increasing horizontal resolution. The deposition ice nucleation scheme is found responsible for a falsely-produced ice cloud aloft that is not observed, biasing the simulated cloud radiative effects and top-of-atmosphere radiative fluxes. This study identifies key deficiencies in cloud parameterizations that continue to challenge convection-permitting models.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC)
• Grant/Contract Number: AC05-76RL01830; AC52-07NA27344
• OSTI ID: 3018095
• Alternate ID(s): OSTI ID: 3017570
• Report Number(s): LLNL--JRNL-2007162; PNNL-SA--213098
• Journal Information: Journal of Geophysical Research. Atmospheres, Journal Name: Journal of Geophysical Research. Atmospheres Journal Issue: 3 Vol. 131; ISSN 2169-8996; ISSN 2169-897X
• Publisher: American Geophysical Union; Wiley
• Country of Publication: United States
• Language: English

Related Subjects

Geosciences
SCREAM
cloud microphysics
cold air outbreak
global convection-permitting model
mixed phase clouds
parameterization