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Implementation and Exploration of Parametrizations of Large-Scale Dynamics in NCAR's Single Column Atmosphere Model SCAM6
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  • Sean Cohen,
  • Adam H Sobel,
  • Michela Biasutti,
  • Shuguang Wang,
  • Isla Ruth Simpson,
  • Andrew Gettelman,
  • I-Kuan Hu
Sean Cohen
Columbia University

Corresponding Author:[email protected]

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Adam H Sobel
Columbia University
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Michela Biasutti
Lamont-Doherty Earth Observatory
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Shuguang Wang
Nanjing University
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Isla Ruth Simpson
National Center for Atmospheric Research (UCAR)
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Andrew Gettelman
Pacific Northwest National Laboratory
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I-Kuan Hu
Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder
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A single column model with parameterized large-scale dynamics is used to better understand the response of steady-state tropical precipitation to relative sea surface temperature under various representations of radiation, convection, and circulation. The large-scale dynamics are parametrized via the weak temperature gradient (WTG), damped gravity wave (DGW), and spectral weak temperature gradient (Spectral WTG) method in NCAR’s Single Column Atmosphere Model (SCAM6). Radiative cooling is either specified or interactive, and the convective parameterization is run using two different values of a parameter that controls the degree of convective inhibition. Results are interpreted in the context of the Global Atmospheric System Studies (GASS) Intercomparison (Daleu et al. 2016). Using the settings given in Daleu et al. (2016), SCAM6 under the WTG and DGW methods produces erratic results, suggestive of numerical instability. However, when key parameters are changed to weaken the strength with which the circulation acts to eliminate tropospheric temperature variations, SCAM6 performs comparably to single column models in the GASS Intercomparison. The Spectral WTG method is less sensitive to changes in convection and radiation than are the other two methods, performing at least qualitatively similarly across all configurations considered. Under all three methods, circulation strength, represented in 1D by grid-scale vertical velocity, is decreased when barriers to convection are reduced. This effect is most extreme under specified radiative cooling, and is shown to come from increased static stability in the column’s reference radiative-convective equilibrium profile. This argument can be extended to interactive radiation cases as well, though perhaps less conclusively.
09 Jun 2023Submitted to ESS Open Archive
11 Jun 2023Published in ESS Open Archive