[Met_help] VECTOR WINDS

[John Halley Gotway]

Luke,

In Point-Stat, if you specify, for example "UGRD/P500" followed by "VGRD/P500", then the U and V components of the wind at 500 mb will be verified as scalar quantities and as vector quantities.  But I 
believe all MET currently does for the vector quantities is dump out the VL1L2 partial sums line.

If you have wind speed as output in your GRIB model data file, you can use Point-Stat to verify it.  During the PB2NC step, you can specify that you'd like wind speed (WIND) derived from the U and V 
components of the wind.  Then in Point-Stat, you can verify wind speed as you would for any other scalar field.

As for wind direction, currently there's no real support for verifying it in MET.  This is an area of development we need to address.  Actually, at the recent WRF-Users conference a group that's been 
using MET at PENN State pointed out the lack of support for verifying wind direction.  The difficulty is HOW to verify it - since it's a "circular" field.  We haven't yet settled on the right way to 
implement it yet.

So it still won't be included in METv1.1, but we plan to work with the PENN State folks to get it in there for the next release.

If you're verifying winds over multiple cases, I'd suggest computing the VL1L2 statistics for each case, summing them up at the end, and deriving statistics from those vector partial sums.  As you go 
through that process, please let us know if you have any suggestions for how better to support verification of winds in MET.

Hope that answers the question.

Thanks,
John

Luke Peffers wrote:
> Hello:
> 
> I would like to verify WRF winds (i.e., wind speed and direction).  I see
> that U and V winds can be verified as vector quantities but am unsure what
> exactly takes place within MET.  Does the point_stat and grid_stat
> configuration file option of using U and V as vectors produce any vector
> error statistics or just what is produced in the Vector L1 and L2 output?
> 
> Thank you
> 
> Luke
> 
> 
> 
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