Global Forecast System (GFS) Model

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Global Forecast System (GFS) Model

• Previous called the Aviation (AVN) and Medium
  Range Forecast (MRF) models.
• Global model and 64 levels
• Relatively primitive microphysics.
• Sophisticated surface physics and radiation
• Run four times a day to 384 hr.
• Major increase in skill during past five years
  derived from using direct satellite radiance in
  the 3DVAR analysis scheme.
• T382 (35 km) over the first 180 hours (7.5 days)
  of the model forecast and T190 (70 km) for 180
  through 384 hours--major implications for
  resolution change!

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GFS

• Just changed vertical coordinates from sigma to
  hybrid sigma/pressure sigma at low levels to
  pressure aloft.

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Vertical coordinate comparison across North
America
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GFS Data Assimilation

• Has a later data cut-off time than the mesoscale
  modelsand thus can get a higher percentage of
  data.
• Uses much more satellite assets..thus improve
  global analysis and forecasts.
• Major gains in southern hemisphere
• Based on 3DVAR

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Skill Improvements (ECMWF)

• Useful skill until
• - day 5
• 2000 - day 7
• 2003 - day 8

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Rapid Update Cycle-RUC
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RUC

• A major issue is how to assimilate and use the
  rapidly increasing array of offtime or continuous
  observations (not a 00 and 12 UTC world anymore!
• Want very good analyses and very good short-term
  forecasts (1-3-6 hr)
• The RUC ingests and assimilates data hourly, and
  then makes short-term forecasts
• Uses the MAPS mesoscale modelwhich uses a hybrid
  sigma/isentropic vertical coordinate
• Resolution 13 km and 50 levels

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13km RUC
Terrain elevation - 100 m interval

• Improvements expected from 13km RUC
• Improved near-surface forecasts
• Improved precipitation forecasts
• Better cloud/icing depiction
• Improved frontal/turbulence forecasts

NCEP computer upgrade allows RUC13 to run in same
time as current RUC20
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Observations used in RUC Data Type
Number Freq. ------------------------------
-------------------- Rawinsonde 80
/12h NOAA profilers 30 /
1h VAD winds 110-130 / 1h
Aircraft (V,temp) 1400-4500 /
1h Surface/METAR 1500-1700 /
1h Buoy/ship 100-150 / 1h GOES
precip water 1500-3000 / 1h GOES cloud
winds 1000-2500 / 1h GOES cloud-top pres
10 km res / 1h SSM/I precip water
1000-4000 / 6h --------------------------------
------------------ GPS precip water 300
/ 1h Mesonet 5000 /
1h METAR-cloud-vis-wx 1500 /
1h -----------------------------------------------
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Cloud analysis variables
NCEP RUC20 operational
RUC13 (at NCEP June 2005)
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• RUC History NCEP (NMC) implementations
• - First operational implementation of RUC
• - 60km resolution, 3-h cycle
• 1998 40km resolution, 1-h cycle,
• - cloud physics, land-sfc model
• 2002 20km resolution
• - addition of GOES cloud data in assimilation
• 2003 Change to 3dVAR analysis from previous OI
• (April)
• 2004 Vertical advection, land use (April)
• PBL-depth for surface assimilation (September)
• 2005 13km resolution, new obs, new model
  physics
• (June)
• 2007 WRF-based Rapid Refresh w/ GSI to replace
  RUC

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13km RUC
20km RUC
Soil moisture 22z - 21 Feb 2005 Dark blue
water
More detailed coastline with 13km resolution
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WRF RUC

• A new version of RUC has been developed, but not
  yet operational that uses the WRF model instead
  of the MAPS model.