Recent Changes Implemented into the Global Forecast System at NMC

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  • 1 National Meteorological Center, Development Division, Global Weather and Climate Modeling Branch
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Abstract

A number of improvements were implemented on 6 March 1991 into the National Meteorological Center's global model, which is used in the global data assimilation system (GDAS), the aviation (AVN) forecast, and the medium-range forecast (MRF):

  • The horizontal resolution of the forecast model was increased from triangular truncation T80 to T126, which corresponds to an equivalent increase in grid resolution from 160 km to 105 km.
  • The use of enhanced orography has been discontinued and replaced by mean orography.
  • A new marine-stratus parameterization was introduced.
  • A new mass-conservation constraint was implemented.
  • The horizontal diffusion in the medium scales was reduced by adopting the Leith formulation.
  • A new, more accurate sea-surface temperature analysis is now used.

In this note, we discuss each of the changes and briefly review the new model performance.

Abstract

A number of improvements were implemented on 6 March 1991 into the National Meteorological Center's global model, which is used in the global data assimilation system (GDAS), the aviation (AVN) forecast, and the medium-range forecast (MRF):

  • The horizontal resolution of the forecast model was increased from triangular truncation T80 to T126, which corresponds to an equivalent increase in grid resolution from 160 km to 105 km.
  • The use of enhanced orography has been discontinued and replaced by mean orography.
  • A new marine-stratus parameterization was introduced.
  • A new mass-conservation constraint was implemented.
  • The horizontal diffusion in the medium scales was reduced by adopting the Leith formulation.
  • A new, more accurate sea-surface temperature analysis is now used.

In this note, we discuss each of the changes and briefly review the new model performance.

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