Improving Stratocumulus Cloud Amounts in a 200‐m Resolution Multi‐Scale Modeling Framework Through Tuning of Its Interior Physics

Journal Article · Wed Mar 06 00:00:00 EST 2024 · Journal of Advances in Modeling Earth Systems

DOI:https://doi.org/10.1029/2023MS003632· OSTI ID:2319047

Peng, Liran  ^[1]; Blossey, Peter N.  ^[2]; Hannah, Walter M.  ^[3]; Bretherton, Christopher S.  ^[4]; Terai, Christopher R.  ^[3]; Jenney, Andrea M.  ^[1]; Pritchard, Michael  ^[5]

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1. Department of Earth System Science University of California, Irvine Irvine CA USA
2. Department of Atmospheric Sciences University of Washington Seattle WA USA
3. Lawrence Livermore National Laboratory Livermore CA USA
4. Department of Atmospheric Sciences University of Washington Seattle WA USA, Allen Institute for Artificial Intelligence Seattle WA USA
5. Department of Earth System Science University of California, Irvine Irvine CA USA, NVIDIA Santa Clara CA USA

Abstract High‐Resolution Multi‐scale Modeling Frameworks (HR)—global climate models that embed separate, convection‐resolving models with high enough resolution to resolve boundary layer eddies—have exciting potential for investigating low cloud feedback dynamics due to reduced parameterization and ability for multidecadal throughput on modern computing hardware. However low clouds in past HR have suffered a stubborn problem of over‐entrainment due to an uncontrolled source of mixing across the marine subtropical inversion manifesting as stratocumulus dim biases in present‐day climate, limiting their scientific utility. We report new results showing that this over‐entrainment can be partly offset by using hyperviscosity and cloud droplet sedimentation. Hyperviscosity damps small‐scale momentum fluctuations associated with the formulation of the momentum solver of the embedded large eddy simulation. By considering the sedimentation process adjacent to default one‐moment microphysics in HR, condensed phase particles can be removed from the entrainment zone, which further reduces entrainment efficiency. The result is an HR that can produce more low clouds with a higher liquid water path and a reduced stratocumulus dim bias. Associated improvements in the explicitly simulated sub‐cloud eddy spectrum are observed. We report these sensitivities in multi‐week tests and then explore their operational potential alongside microphysical retuning in decadal simulations at operational 1.5° exterior resolution. The result is a new HR having desired improvements in the baseline present‐day low cloud climatology, and a reduced global mean bias and root mean squared error of absorbed shortwave radiation. We suggest it should be promising for examining low cloud feedbacks with minimal approximation.

• Sponsoring Organization: USDOE
• Grant/Contract Number: DE‐AC52‐07NA27344; DE‐SC0023368
• OSTI ID: 2319047
• Alternate ID(s): OSTI ID: 2319049
• Journal Information: Journal of Advances in Modeling Earth Systems, Journal Name: Journal of Advances in Modeling Earth Systems Vol. 16 Journal Issue: 3; ISSN 1942-2466
• Publisher: American Geophysical Union (AGU)
• Country of Publication: United States
• Language: English