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Impacts of Model Horizontal Resolution on Mean Sea-Surface Temperature Biases in the Community Earth System Model
  • +6
  • Gaopeng Xu,
  • Ping Chang,
  • Sanjiv Ramachandran,
  • Gokhan Danabasoglu,
  • Stephen Yeager,
  • Justin Small,
  • Qiuying Zhang,
  • Zhao Jing,
  • Lixin Wu
Gaopeng Xu
Texas A&M University

Corresponding Author:[email protected]

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Ping Chang
TAMU
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Sanjiv Ramachandran
Texas A & M University
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Gokhan Danabasoglu
National Center for Atmospheric Research (NCAR)
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Stephen Yeager
National Center for Atmospheric Research
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Justin Small
National Center for Atmospheric Research (UCAR)
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Qiuying Zhang
Texas A&M University
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Zhao Jing
Ocean University of China
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Lixin Wu
Key Laboratory of Physical Oceanography, Ocean University of China; and Qingdao National Laboratory of Marine Science and Technology, Qingdao 266100, China
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Abstract

Impacts of model horizontal resolution on sea-surface temperature (SST) biases are studied using high-resolution (HR) and low-resolution (LR) simulations with the Community Earth System Model (CESM) where the nominal resolutions are 0.1° for ocean and sea-ice and 0.25° for atmosphere and land in HR, and 1° for all component models in LR, respectively. Results show that, except within eastern boundary upwelling systems, SST is warmer in HR than LR. Globally averaged surface ocean heat budget analysis indicates that 1°C warmer global-mean SST in HR is mainly attributable to stronger nonlocal vertical mixing and shortwave heat flux, with the former prevailing over the latter in eddy-active regions. In the tropics, nonlocal vertical mixing is slightly more important than shortwave heat flux for the warmer SST in HR. Further analysis shows that the stronger nonlocal mixing in HR can be attributed to differences in both the surface heat flux and shape function strength used in the parameterization. In addition, the shape function shows a nonlinear relationship with surface heat flux in HR and LR, modulated by the eddy-induced vertical heat transport. The stronger shortwave heat flux in HR, on the other hand, is mainly caused by fewer clouds in the tropics. Finally, investigation of ocean advection reveals that the improved western boundary currents in HR also contribute to the reduction of SST biases in eddy-active regions.