RUC/MAPS Frequently Asked Questions

Q: Why are precipitation fields missing (flagged values) in RUC analysis fields? 11/07/2007
Answer: Precipitation fields only have non-flagged values for forecast output times, not analysis time (f00), since the RUC doesn't analyze precip, so this is as expected. Precip fields should be available from 1h forecasts onward.

Q: What is the difference between the NCEP and GSD (formerly FSL) versions of the RUC?

Operational NCEP 13km RUC (operational implementation on 28 June 2005)
Backup RUC13 at GSD - least frequently changed version of RUC. Runs out to 48h every 12h, out to 24h every 3h, out to 12h otherwise. As of 4/4/07, includes radar reflectivity assimilation and other changes previously made to development RUC13.
Development RUC13 at GSD - more experimental version of RUC. See http://ruc.noaa.gov/13km_RUC.changelog.html for latest changes. Runs out to 72h every 12h, out to 48h every 3h. (11/07/2007 - current different only in new variation of Grell-Devenyi scheme w/ non-local subsidence warming)

20km dev RUC - Uses same code as operational RUC13, but running at 20km horizontal resolution.
20km dev-2 RUC at GSD - Same as 20km dev RUC except that dev2 RUC assimilates TAMDAR aircraft observations.

26Jan05 - Q: If the height from the lowest level in the RUC native coordinate matches the RUC model terrain height exactly, how can the winds from the lowest native level be non-zero?
The lowest native level is 5m above the surface, strictly speaking, except for its calculations of heights. In other words, the winds, virtual potential temperature, and water vapor mixing ratio can all be considered as 5m above the surface in regard to the atmospheric/land-water boundary. Note Fig. 6 in the Feb 2004 Monthly Weather Review paper about the RUC model on p.482, which shows 2.5m as the half-point between the actual surface and the 5m first atmospheric level.
Note also that there are 2-m and 10-m winds in the native file, reduced in a post-processing via Monin-Obukhov similarity.

Q: (an old one) What is the difference between RUC and MAPS?
The RUC is the operational version run at NCEP. Versions of the RUC are also run at FSL as a backup to the operational run and as test versions. MAPS is a now-ancient name used in the early-mid 1990s for development versions of the RUC.

Q: What is the history of the operational RUC?

1994 - RUC starts running at NCEP, first version with 60-km horizontal resolution and 3-h assimilation cycle.
1998 - Implementation of 40-km RUC with 1-h assimilation cycle
2002 - Implementation of 20-km RUC with 1-h assimilation cycle
2005 - Implementation of 13-km RUC with 1-h assimilation cycle
History of RUC system with detailed description - written April 2004 - from NWP 50th anniversary symposium

Q: What is the wind direction shown in RUC weather maps?
The wind flags for these maps are the usual convention for weather maps, showing the direction from which the wind is coming. If the wind flag is toward the west, that means that the wind direction is from the west toward the east. Also, note that the RUC grid map projection is not Mercator (it's Lambert conformal), so right-to-left winds are generally not due west (except at 95 deg W). Finally, wind in RUC grids are grid-relative for direction, not lat/lon-relative. (see last FAQ item for information on rotation to lat/lon-relative)

Q: Why do I get forecasts from different runs when clicking the "All Times" button for RUC or WRFRUC products?
This can sometimes happen because early output times from new runs are processed into products while the run is still continuing in order to make available the latest products. Also, sometimes runs may be missing or products may be missing because of computer/disk outages.

Q: Could you please run the RUC model out past 12 hours?
Almost every RUC version run at GSD goes beyond 12h, with the Backup RUC13 out to 48h, and the dev RUC13 out to 72h (for 00z and 12z init times).

Q: Are the mass and velocity values defined at the same grid point in RUC output grids?
The answer is yes. The native RUC model horizontal grid is an Arakawa C grid, in which there is staggering. This is in the model itself. However, all RUC wind output, even in the hybrid-b native vertical coordinate, is unstaggered back onto the mass points. So that is what you are seeing in any output file, unstaggered winds.

Q: Do you have FORTRAN code for converting the u and v wind components aligned to the RUC grid to components with respect to true north (meteorological standard)?
Here is a code snippet that should do the job.

      PARAMETER ( ROTCON_P   =  0.422618      )
      PARAMETER ( LON_XX_P   = -95.0          )
C**  ROTCON_P          R  WIND ROTATION CONSTANT, = 1 FOR POLAR STEREO
C**                         AND SIN(LAT_TAN_P) FOR LAMBERT CONFORMAL
C**  LON_XX_P          R  MERIDIAN ALIGNED WITH CARTESIAN X-AXIS(DEG)
C**  LAT_TAN_P         R  LATITUDE AT LAMBERT CONFORMAL PROJECTION
C**                         IS TRUE (DEG)
      PARAMETER ( LAT_TAN_P  =  25.0          )

        do j=1,ny_p
        do i=1,nx_p
           angle2 = rotcon_p*(olon(i,j)-lon_xx_p)*0.017453
           sinx2 = sin(angle2)
           cosx2 = cos(angle2)
         do k=1,nzp_p
           ut = u(i,j,k)
           vt = v(i,j,k)   
           un(i,j,k) = cosx2*ut+sinx2*vt
           vn(i,j,k) =-sinx2*ut+cosx2*vt
          end if
         end do
        end do

Please credit the NOAA/Earth System Research Laboratory, RUC development group, if you wish to use any pictures from this web site.

This page prepared by Stan Benjamin