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Reducing Numerical Diffusion in Dynamical Coupling between Atmosphere and Ocean in Community Earth System Model (CESM), version 1.2.1
  • Jialiang Ma,
  • Shiming Xu,
  • Bin Wang
Jialiang Ma
Department of Earth System Science, Tsinghua University
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Shiming Xu
Department of Earth System Science, Tsinghua University

Corresponding Author:[email protected]

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Bin Wang
Tsinghua University
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Abstract

Climate models contain atmospheric and oceanic components that are coupled together to simulate the thermodynamic and dynamic processes during air-sea interactions. Community Earth System Model (CESM, version 1.2.1) is a state-of-the-art coupled model that is widely used and participates in Coupled Model Intercomparison Projects. Community Atmospheric Model (CAM), the atmospheric component of CESM, is based on the finite-volume dynamic core, which utilizes staggered Arakawa-D grids. However, the dynamics-physics (D-P) coupling in CAM causes the prognostic winds of the dynamic core be interpolated onto non-staggered locations, which affects the wind structure for computing the air-sea interaction and dynamical coupling. In this study we propose a new scheme that eliminates the extra interpolation during D-P coupling for the atmosphere-ocean interaction. By numerical experiments and comparative study of the new scheme, we show that it improves the simulated climatology in key regions including eastern-boundary upwelling regions and Southern Oceans. In turn, existing problems of the model, such as warm SST biases, are reduced. The new scheme contain code changes in CAM and the coupler, and they are provided as open-source files. Similar approaches can also be adopted in coupled models that utilize the atmospheric components with on staggered dynamics and physics, such as spectral-element method based CAM.
Sep 2020Published in Journal of Advances in Modeling Earth Systems volume 12 issue 9. 10.1029/2020MS002052