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Seasonal cycle of idealized polar clouds: large eddy simulations driven by a GCM
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  • Xiyue Zhang,
  • Tapio Schneider,
  • Zhaoyi Shen,
  • Kyle G Pressel,
  • Ian Eisenman,
  • Xiyue Zhang
Xiyue Zhang
National Center for Atmospheric Research

Corresponding Author:[email protected]

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Tapio Schneider
California Institute of Technology, California Institute of Technology
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Zhaoyi Shen
California Institute of Technology, California Institute of Technology
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Kyle G Pressel
Pacific Northwest National Laboratory, Pacific Northwest National Laboratory
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Ian Eisenman
UC San Diego, UC San Diego
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Xiyue Zhang
Johns Hopkins University

Corresponding Author:[email protected]

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Abstract

The uncertainty in polar cloud feedbacks calls for process understanding of the cloud response to climate warming. As an initial step toward improved process understanding, we investigate the seasonal cycle of polar clouds in the current climate by adopting a novel modeling framework using large eddy simulations (LES), which explicitly resolve cloud dynamics. Resolved horizontal and vertical advection of heat and moisture from an idealized general circulation model (GCM) are prescribed as forcing in the LES. The LES are also forced with prescribed sea ice thickness, but surface temperature, atmospheric temperature, and moisture evolve freely without nudging. A semigray radiative transfer scheme without water vapor and cloud feedbacks allows the GCM and LES to achieve closed energy budgets more easily than would be possible with more complex schemes. This enables the mean states in the two models to be consistently compared, without the added complications from interaction with more comprehensive radiation. We show that the LES closely follow the GCM seasonal cycle, and the seasonal cycle of low-level clouds in the LES resembles observations: maximum cloud liquid occurs in late summer and early autumn, and winter clouds are dominated by ice in the upper troposphere. Large-scale advection of moisture provides the main source of water vapor for the liquid-containing clouds in summer, while a temperature advection peak in winter makes the atmosphere relatively dry and reduces cloud condensate. The framework we develop and employ can be used broadly for studying cloud processes and the response of polar clouds to climate warming.
Jan 2022Published in Journal of Advances in Modeling Earth Systems volume 14 issue 1. 10.1029/2021MS002671