[Met_help] stat_analysis on UGRD / VGRD

John Halley Gotway johnhg at rap.ucar.edu
Fri May 1 08:21:45 MDT 2009


You'll need to modify slightly how you're running Point-Stat to treat UGRD and VGRD as scalars rather than as vectors.

Please take a look at the Point-Stat configuration file.  Here's an excerpt:
//    NOTE: To verify winds as vectors rather than scalars,
//          specify UGRD (or 33) followd by VGRD (or 34) with the
//          same level values.

In the config file, if you set "fcst_field" to be UGRD followed by VGRD at the same level (e.g. FCST_FIELD = [ "UGRD/Z2", "VGRD/Z2" ];) the winds will be treated as vectors, not scalars.  So a VL1L2
line will be produced for them and no SL1L2 lines.

But you'd like to have SL1L2 lines, and you don't care about the VL1L2.  One easy thing to do would be to just reverse the order: FCST_FIELD = [ "VGRD/Z2", "UGRD/Z2" ];
Then the order convention won't apply, and they'll be treated as scalars, not vectors.

I realize that this ordering convention is a bit unfortunate.  However, vector winds are the only case where we have to *combine* two fields and analyze them simultaneously.  All of the other fields
are simple scalars.

Hope that does the trick for you,

Case, Jonathan (MSFC-VP61)[Other] wrote:
> John,
> I had problems running stat_analysis on the UGRD and VGRD variables.  I thought that they would work the same way as the other scalars, but there isn't any SL1L2 output for the individual wind components.   Without venturing into the matched pairs, I tried to run on the VL1L2 data, but that isn't working for me.
> So, what is the best way to summarize error stats for the individual UGRD and VGRD wind components?  I want to have a scalar average of the individual components, not calculate an overall vector error.
> Thanks,
> Jon
> ***********************************************************
> Jonathan Case, ENSCO, Inc.
> Aerospace Sciences & Engineering Division
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