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Vaughan Phillips

Research in the Area of Clouds, Aerosols and Climate

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Sensitivity of Arctic Clouds to Ice Microphysical Processes in the NorESM2 Climate Model

Author

  • Georgia Sotiropoulou
  • Anna Lewinschal
  • Paraskevi Georgakaki
  • Vaughan T.J. Phillips
  • Sachin Patade
  • Annica M.L. Ekman
  • Athanasios Nenes

Summary, in English

Ice formation remains one of the most poorly represented microphysical processes in climate models. While primary ice production (PIP) parameterizations are known to have a large influence on the modeled cloud properties, the representation of secondary ice production (SIP) is incomplete and its corresponding impact is therefore largely unquantified. Furthermore, ice aggregation is another important process for the total cloud ice budget, which also remains largely unconstrained. In this study, we examine the impact of PIP, SIP, and ice aggregation on Arctic clouds, using the Norwegian Earth System Model, version 2 (NorESM2). Simulations with both prognostic and diagnostic PIP show that heterogeneous freezing alone cannot reproduce the observed cloud ice content. The implementation of missing SIP mechanisms (collisional breakup, drop shattering, and sublimation breakup) in NorESM2 improves the modeled ice properties, while improvements in liquid content occur only in simulations with prognostic PIP. However, results are sensitive to the description of collisional breakup. This mechanism, which dominates SIP in the examined conditions, is very sensitive to the treatment of the sublimation correction factor, a poorly constrained parameter that is included in the utilized parameterization. Finally, variations in ice aggregation treatment can also significantly impact cloud properties, mainly through their impact on collisional breakup efficiency. Overall, enhancement in ice production through the addition of SIP mechanisms and the reduction in ice aggregation (in line with radar observations of shallow Arctic clouds) result in enhanced cloud cover and decreased TOA radiation biases, compared to satellite measurements, especially during the cold months.

Department/s

  • Dept of Physical Geography and Ecosystem Science
  • eSSENCE: The e-Science Collaboration
  • MERGE: ModElling the Regional and Global Earth system

Publishing year

2024-08

Language

English

Pages

4275-4290

Publication/Series

Journal of Climate

Volume

37

Issue

16

Document type

Journal article

Publisher

American Meteorological Society

Topic

  • Meteorology and Atmospheric Sciences

Keywords

  • Arctic
  • Climate models
  • Cloud microphysics
  • Cloud parameterizations
  • Clouds
  • Secondary ice production

Status

Published

ISBN/ISSN/Other

  • ISSN: 0894-8755