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1

WRF:

Weather Research and Forecasting Model

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WRF: Weather Research and Forecasting Model 
–  Used for

 both research and operational  forecasting

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WRF: Weather Research and Forecasting  Model 
–  Used for both research and operational  forecasting 
•  It is a supported “community model”, i.e.

a  free and shared resource with distributed development and centralized support 

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It is a supported “community model”, i.e. a  free and shared resource with distributed  development and centralized support 
•  Its development is led by

NCAR, NOAA/ ESRL and NOAA/NCEP/EMC with  partnerships at AFWA, FAA, DOE/PNNL and  collaborations with universities and other government agencies in the US and overseas

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WRF has two dynamical cores:

The Advanced Research WRF (ARW) and

Nonhydrostatic MesoscaleModel (NMM)

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WRF has two dynamical cores: The Advanced Research WRF  (ARW) and Nonhydrostatic MesoscaleModel (NMM) 
–  Dynamical core includes mostly

  • advection,
  • pressure gradients,
  • Coriolis,
  • buoyancy,
  • filters,
  • diffusion, and
  • timestepping

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The Advanced Research WRF  (ARW) and Nonhydrostatic MesoscaleModel (NMM)

both are

Eulerianmass dynamical cores with terrain-following  vertical coordinates

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ARW support and development are centered at

NCAR/MMM

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NMM development is centered at

NCEP/EMC and support is  provided by NCAR/DTC (operationally now only used for HWRF)

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The Advanced Research WRF (ARW) and Nonhydrostatic MesoscaleModel (NMM)

Both are downloadable in  

 the same WRF tar file

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The Advanced Research WRF (ARW) and Nonhydrostatic MesoscaleModel (NMM)

what are the things shared between the dynamical cores

  • Physics,
  • the software framework, and
  • parts of data pre- and post-processing

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ARW and NMM can be used for

  • Atmospheric physics/parameterization research 
  •  Case-study research 
  • Real-time NWP and forecast system research 
  • Data assimilation research 
  • Teaching dynamics and NWP

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ARW only can be used for

  • Regional climate and seasonal time-scale research 
  • Coupled-chemistry applications 
  • Global simulations 
  • Idealized simulations at many scales (e.g. convection,  baroclinic waves, large eddy simulations) 

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WRF Modeling System Flow chart

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Modeling System Components 

WRF Pre-processing System 

WRF Model (ARW and NMM dynamical cores)

Graphics and verification tools including MET

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explain:

WRF Pre-processing System 

  • Real-data interpolation for NWP runs (WPS) 
  • Program for adding more observations to analysis (obsgrid)

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explain:

WRF Model (ARW and NMM dynamical cores)

  • Initialization programs for real and (for ARW) idealized data (real.exe/ideal.exe) 
  • –  Numerical integration program (wrf.exe)

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WPS and WRF Program Flow

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Real-Data Applications of WRF

  • Numerical weather prediction 
  •  Meteorological case studies 
  • Regional climate 
  • Applications: air quality, wind energy, hydrology, etc

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Real-Data Applications need 

time-independent information for chosen domain(simulation grid area) 

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Real-Data Applications 

GEOGRID program

  • Map projection information
  • Topographic information

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Real-Data Applications 

GEOGRID program

Map projection information

 

  • 2d gridded latitude,
  • longitude,
  • Coriolis parameter,
  • map-scale factors, etc

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Real-Data Applications 

GEOGRID program

Topographic information

2d gridded elevation,

vegetation and soil categories, etc.

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Real-Data Applications need the following

  • Need time-dependent information 
  • Initial conditions (initial analysis time) 
  • Boundary conditions (later times)
    •  except if running WRF globally 
  • UNGRIB and METGRIDprograms

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Real-Data Applications

UNGRIBand METGRIDprograms

  • 3d fields of horizontal wind, temperature, geopotential height, relative humidity 
  •  2d fields of surface or sea-level pressure, surface  temperature, relative humidity, horizontal winds 
  •   Time-sensitive land-surface fields: snow-cover,  soil temperature, soil moisture 

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Real-Data Applications

Regional domains need

specified lateral boundary conditions at later times (e.g. every 6 hours) through forecast period

  • 3d fields of horizontal wind, temperature, geopotential height, water vapor 
  •  2d field of surface pressure

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Long simulations (> 1 week) also need

lower boundary condition at later times 

  • 2d fields of sea-surface temperature, sea-ice, vegetation fraction

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Lateral Boundary Conditions (linear in time) 
–  The wrfbdyfile contains

later gridded information at model points in a zone (e.g.) 5 points wide around the domain

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Lateral Boundary Conditions (linear in time) 
–  The wrfbdyfile contains later gridded information at model points in a zone (e.g.) 5 points wide  around the domain 
–  The boundary fields are

linearly time-interpolated from boundary times to the current model time

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Lateral Boundary Conditions (linear in time) 
–  The wrfbdyfile contains later gridded information at model points in a zone (e.g.) 5 points wide 
around the domain 
–  The boundary fields are linearly time-interpolated from boundary times to the current model time 
–  This specifies

the outer values, and is used to nudge the next 4 interior points