Production suite overview

Regional Forecast System

HIGHLIGHTS

• Short-range regional forecast model - the GEM (Global Environmental Multiscale) model (Grid)

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  • non-uniform horizontal grid with 15 km resolution over central window, rotated at ~90 degrees - 58 eta vertical levels
  • 48 hour forecast twice daily (00 UTC and 12 UTC)
  • Operational since May 18, 2004
    

• Regional Variational Assimilation System
  • Operational since May 18, 2004
    
  • Analysis on eta levels with TOVS/AMDAR/ACARS since Jan 11 2001

• High resolution Model Applications Project (Reference)
  • 10 km horizontal resolution - 35 vertical levels - 24 hour forecast
  • Experimental/operational since Oct. 24 1997

DATA ASSIMILATION & INITIALIZATION

• 12-hour regional cycles, run twice a day (00Z and 12Z). A global analysis initiates the regional cycle.

• 3D Var analysis

• Calculation of analysis increments in spectral space (the analysis is obtained by adding the increments to the trial field).
  • T108 spectral resolution
  • 28 eta levels

• Digital filter initialization

  • 3 hour span

• Reference [PDF Version]

GEM MODEL DYNAMICS

• Hydrostatic primitive equations

• Discretisation:

  • time - Implicit two time-level semi-Lagrangian scheme; time step = 450 sec

  • space - 3D finite elements

• 575 x 641 variable-resolution lat-lon grid

  • 0.1375° (~15 km) uniform-resolution window covering most of North America

  • 432 X 565 grid points in central window

• 58 eta levels, top at 10 hPa
  

• Boundary conditions:

  • periodicity in the horizontal

  • No motion across eta=0,1 surfaces

• horizontal diffusion on all prognostic variables

• Stratospheric sponge on the 4 upper levels

• Reference [PDF Version]

MODEL PHYSICS

• Solar and infrared radiation interact with water vapor, carbon dioxide, ozone, and clouds

• ISBA surface scheme

  • includes prognostic variable for surface and soil temperatures, as well as for soil volumetric water contents.

• Turbulence in the planetary boundary layer through vertical diffusion, diffusion coefficients based on stability and kinetic energy

• Surface layer based on Monin-Obukhov similarity theory

• Shallow convection scheme (non precipitating)

• Kain-Fritsch deep convection scheme

• Sundqvist condensation scheme for stratiform precipitation

• Gravity wave drag

• Reference [PDF Version]

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Environment Canada's World Wide Web Site.