Preprints
https://doi.org/10.5194/egusphere-2022-980
https://doi.org/10.5194/egusphere-2022-980
 
22 Nov 2022
22 Nov 2022
Status: this preprint is open for discussion.

Importance of Ice Nucleation and Precipitation on Climate with the Parameterization of Unified Microphysics Across Scales version 1 (PUMASv1)

Andrew Gettelman1, Hugh Morrison1, Trude Eidhammer1, Katherine Thayer-Calder1, Jian Sun1, Richard Forbes3, Zachary McGraw4,5, Jiang Zhu1, Trude Storelvmo2, and John Dennis1 Andrew Gettelman et al.
  • 1National Center for Atmospheric Research, Boulder, CO, USA
  • 2Department of Meteorology, University of Oslo, Oslo, Norway
  • 3European Centre for Medium Range Weather Forecasts, Reading, UK
  • 4Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA
  • 5NASA Goddard Institute for Space Studies, NY, USA

Abstract. Cloud microphysics is critical for weather and climate prediction. In this work, we document updates and corrections to the cloud microphysical scheme used in the Community Earth System Model (CESM) and other models. These updates include a new nomenclature for the scheme, and the ability to run the scheme on Graphics Processing Units (GPUs). The main science changes include removing an ice number limiter and associated changes to ice nucleation, adding vapor deposition onto snow, and introducing an implicit numerical treatment for sedimentation. We also detail the improvements in computational performance that can be achieved with GPU acceleration. We then show the impact of these scheme changes on (A) mean state climate, (B) cloud feedback response to warming and (C) aerosol forcing. We find that corrections are needed to the immersion freezing parameterization without a limit on ice number. We also find that the revised scheme produces less liquid and ice, but that this can be adjusted by changing the loss process for cloud liquid (autoconversion). Furthermore, there are few discernible effects of the PUMAS changes on cloud feedbacks, but some significant reductions in the magnitude of Aerosol Cloud Interactions (ACI). Small cloud feedback changes appear to be related to the implicit sedimentation scheme, with a number of factors affecting ACI.

Andrew Gettelman et al.

Status: open (until 17 Jan 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Andrew Gettelman et al.

Andrew Gettelman et al.

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Short summary
Clouds are a critical part of weather and climate prediction. In this work, we document updates and corrections to the description of clouds used in several Earth System Models. These updates include the ability to run the scheme on Graphics Processing Units (GPUs) and changes to the numerical description of precipitation, as well as a correction to ice number. There are big improvements in computational performance that can be achieved with GPU acceleration.