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RUC isobaric output-smoothed?

Posted By: Todd Hutchinson
Date: 5-September-03 1639Z

Hi,

Questions:

1. Are the RUC output wind fields on pressure surfaces smoothed?
2. If so, why are they smoothed?
3. Is unsmoothed data available anywhere?

Details:

I've been trying to use the RUC isobaric output to initialize some MM5 model runs. In doing so, I have noticed that MM5 has a large spinup period when using the RUC for initialization (as compared to initializing with the Eta). In investigating further, I have found that the 500 mb RUC wind fields at forecast hour 0 appear to be much smoother than the 500 mb Eta 0-hour forecast wind fields valid at the same time.

Further, in comparing the RUC wind field and vertical motion, there does not appear to be much convergence/divergence near areas of rising/sinking motion (this is a very subjective evaluation).

I suspect that the wind field (on pressure coordinates) is being smoothed. I found the following statement in the RUC Technical Procedures Bulletin:

6.c. Basic 3-D output variables
There is no change in the 3-dimensional variables output by the RUC20 for either bgrb (native) or pgrb (isobaric) fields resulting from post-processing changes except that isobaric heights from the RUC20 are smoother due to extra smoothing passes.

This says that "isobaric heights" are smoothed. But, it does not say whether winds on isobaric surfaces are smoothed.

Thank you,

Todd Hutchinson

Messages In This Thread

RUC isobaric output-smoothed? -- Todd Hutchinson -- 5-September-03 1639Z
Re: RUC isobaric output-smoothed? -- Stan Benjamin -- 5-September-03 1855Z
Re: RUC isobaric output-smoothed? -- Todd Hutchinson -- 5-September-03 1855Z

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