Mesoscale Parallel Experiment Log

Experiment Name
Eta-32 with assimilation of NEXRAD radial winds
Parallel Slot
ETAL
Control Slot
ETAV (to 00Z 2002/3/6)
ETAY (from 12Z 2002/3/6)
Start date of parallel experiment
00Z 2002/02/22
End date of parallel experiment
00Z 2002/06/03
Environmental Modeling Center scientists
Ying Lin, Dave Parrish, Eric Rogers
Abstract (including Motivation, Hypothesis and Method)
The Eta-32 parallel system is being used to test the assimilation of NEXRAD radial wind velocity data
OBSERVATIONAL AND ANALYSIS CHANGES
  • Radial wind data from NEXRAD are assimilated using the eta 3DVAR analysis. The raw data is converted into super-obs with a spatial resolution of 1 km and 6 degrees of azimuth. All NEXRAD winds within +/- 1.5 hours of the analysis time are used.
  • Define radar beam vertical extent to increase at the rate of 20m/km. This is about 20% larger than the actual beam size, to allow for beam propagation uncertainty.
  • Winds at all eta levels covered by the radar beam are adjusted so that the observation is as close as possible to the interval between the minimum and maximum wind at the selected levels. (The min and max are not the actual min and max but those derived from a straight line fit to the winds. This is done to simplify the computation of the gradient of the forward model implied by this process).
  • All winds, out to the maximum range of the radar can be used with the above defined forward model. Bill Facey increased the distance parameter in the superob code so that superobs are formed out to the maximum radar range (250km).
  • All VAD wind observation quality marks are collocated in the vertical in 500m bins with the corresponding radar winds. If there is no VAD observation, or if the quality mark is larger than 3, then the corresponding radar winds are not used. This combines the bird algorithm and other checks used on the VAD winds.
  • If the beam envelope extends below the eta model terrain height, the corresponding radar wind is not used.
  • If the superob error is larger than 6m/sec, the radar wind is not used.
  • Gross checks are the same as for conventional winds (residual < 35m/sec)
  • Experiment changes log
    Implementation changes list
    Product changes list
    Background links
    Evaluation of parallel results
    Daily forecast maps
    Daily forecast stats
    Verification of precipitation and against rawinsondes / surface data
    Conclusion

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    Page Last Modified: January 16, 2002