Rapid Refresh (RAP) and High-Resolution Rapid Refresh (HRRR) Forum
3dVAR implementation planned for oper RUC on 20 May
Posted By: Stan Benjamin
Date: 19-May-03 2027Z
A Technical Procedures Bulletin with more detail on the change, verification statistics, and examples of comparisons of analysis and forecast is available online at http://ruc.fsl.noaa.gov/ppt_pres/RUC-3dvar-tpb-May03.htm.
Please write if you have questions.
The following is a "notice of intent to change" the RUC analysis to a 3DVAR version, distributed last Friday:
Brief Description of Changes:
An upgrade to the NCEP Rapid Update Cycle analysis from an optimal interpolation (OI) technique to a 3-d variational (3DVAR) technique. As described in the Notice of Intent to Change in Feb 2002, the RUC 3DVAR implementation was deferred from the original 20-km RUC implementation
The RUC 3DVAR analysis uses the same hybrid isentropic-sigma coordinate as used in the RUC OI analysis (and RUC forecast model). Overall, the RUC 3DVAR provides
Also, a few minor changes to the RUC post-processing are also being implemented with this change package, including addition of 0-1 km helicity and some small fixes.
A Technical Procedures Bulletin describing these changes in detail can be found at http://ruc.fsl.noaa.gov/ppt_pres/RUC-3dvar-tpb-May03.htm.
Reasons for Changes:
To improve forecast accuracy, fit to observations, to provide quieter short-range forecasts and the capability for assimilating indirect observations such as radar radial winds, satellite radiances, and wind speeds.
More detail is provided in the online TPB at:
Schedule for change:
Final testing : Ongoing since November 2002
Description of testing:
Initial testing was done at NOAA/FSL for retrospective periods in May 2000 and February 2001. Testing at NCEP was performed for a parallel real-time cold season period from November 2002 through January 2003. A retrospective warm season period test was conducted for a 28-day period during August 2002 into early September 2002.
Again, this testing is described in more detail with graphics of examples and overall statistics in the RUC 3DVAR TPB at
Points of Contact:
Stan Benjamin Stan.Benjamin@noaa.gov 303-497-6387
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