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The Implementation of Framework for Improvement by Vertical Enhancement (FIVE) into Energy Exascale Earth System Model (E3SM)
  • Hsiang-He Lee,
  • Peter A Bogenschutz,
  • Takanobu Yamaguchi
Hsiang-He Lee
Lawrence Livermore National Laboratory

Corresponding Author:[email protected]

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Peter A Bogenschutz
Lawrence Livermore National Laboratory
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Takanobu Yamaguchi
NOAA Earth System Research Laboratory
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The low cloud bias in global climate models (GCMs) remains an unsolved problem. Coarse vertical resolution in GCMs has been suggested to be a significant cause of low cloud bias because planetary boundary layer parameterizations cannot resolve sharp temperature and moisture gradients often found at the top of subtropical stratocumulus layers. This work aims to lessen the low cloud problem by implementing a new computational method, the Framework for Improvement by Vertical Enhancement (FIVE), into the Energy Exascale Earth System Model (E3SM). Three physics schemes representing microphysics, radiation, and turbulence as well as vertical advection are interfaced to vertically enhanced physics (VEP), which allows for these processes to be computed on a higher vertical resolution grid compared to the rest of the E3SM model. We demonstrate the better representation of subtropical boundary layer clouds with FIVE while limiting additional computational cost from the increased number of levels. When the vertical resolution approaches the LES-like vertical resolution in VEP, the climatological low cloud amount shows a significant increase of more than 30% in the southeastern Pacific Ocean. Besides the improvement of low-level cloud amount, the skill scores of mid- and high-level cloud amounts are not negatively impacted partly because FIVE can avoid negative consequences of running deep convection parameterization at high vertical resolution.