[Met_help] [rt.rap.ucar.edu #60694] History for Grid-Stat output question

[John Halley Gotway via RT]

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  Initial Request
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I have generated the CNT output file from a run where the forecast grid contained UGRD and VGRD but no WIND or WDIR data. The gridded observation data contained UGRD, VGRD, WIND and WDIR data.

My config file specified the fields to be verified as: UGRD, VGRD and WIND.

How are the error stats contained in the CNT file for WIND calculated since there are no forecast grid values for WIND from which to generate a matched pair difference?

If I were to specify an additional field to be verified as WDIR, would the CNT error stats for WDIR be similarly calculated? Is so, how would they be calculated?

Thanks.

R/
John



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  Complete Ticket History
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Subject: Re: [rt.rap.ucar.edu #60694] Grid-Stat output question
From: John Halley Gotway
Time: Tue Mar 19 11:58:45 2013

John,

Good question.  The first paragraph of page 4-11 in the MET user's
guide discusses this.

Suppose you request WIND (wind speed) from a GRIB file that only
contains the corresponding U and V components.  MET first looks for
the record of wind speed you requested.  If it can't find it, it
looks for the corresponding U and V components.  If they are defined
to be grid-relative, it rotates them to being earth-relative.  And it
derives wind speed on the fly for you.

Please try increasing the verbosity level up to 3 (-v 3), and then
rerun the MET tool.  You should see log messages telling you that it's
deriving wind speed for you.

Wind direction is a different matter entirely.  The MET tools don't
verify it directly since it's a "circular" variable.  The current
support for verifying wind direction in MET is described in
section 8.2.6 of the user's guide.

Hope that helps.

Thanks,
John

On 03/19/2013 09:43 AM, Raby, John W USA CIV via RT wrote:
>
> Tue Mar 19 09:43:00 2013: Request 60694 was acted upon.
> Transaction: Ticket created by john.w.raby2.civ at mail.mil
>         Queue: met_help
>       Subject: Grid-Stat output question
>         Owner: Nobody
>    Requestors: john.w.raby2.civ at mail.mil
>        Status: new
>   Ticket <URL:
https://rt.rap.ucar.edu/rt/Ticket/Display.html?id=60694 >
>
>
> I have generated the CNT output file from a run where the forecast
grid contained UGRD and VGRD but no WIND or WDIR data. The gridded
observation data contained UGRD, VGRD, WIND and WDIR data.
>
> My config file specified the fields to be verified as: UGRD, VGRD
and WIND.
>
> How are the error stats contained in the CNT file for WIND
calculated since there are no forecast grid values for WIND from which
to generate a matched pair difference?
>
> If I were to specify an additional field to be verified as WDIR,
would the CNT error stats for WDIR be similarly calculated? Is so, how
would they be calculated?
>
> Thanks.
>
> R/
> John
>

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Subject: Grid-Stat output question
From: Raby, John W USA CIV
Time: Tue Mar 19 12:47:33 2013

Classification: UNCLASSIFIED
Caveats: NONE

John -

Thanks for pointing out the reference to the User's Guide. I had
missed that
part when I did a cursory search.

Very helpful. My verbosity is set to 2 right now. I'll give it a try
with 3.

For direction, I am familiar with the way Point-Stat did it since we
typically
set the output flag to generate the VL1L2 lines and then used Stat-
Analysis to
calculate the direction error stats. Grid-Stat should work the same
way.

R/
John


-----Original Message-----
From: John Halley Gotway via RT [mailto:met_help at ucar.edu]
Sent: Tuesday, March 19, 2013 11:59 AM
To: Raby, John W CIV (US)
Cc: Vaucher, Gail T CIV (US)
Subject: Re: [rt.rap.ucar.edu #60694] Grid-Stat output question

John,

Good question.  The first paragraph of page 4-11 in the MET user's
guide
discusses this.

Suppose you request WIND (wind speed) from a GRIB file that only
contains the
corresponding U and V components.  MET first looks for the record of
wind
speed you requested.  If it can't find it, it looks for the
corresponding U
and V components.  If they are defined to be grid-relative, it rotates
them to
being earth-relative.  And it derives wind speed on the fly for you.

Please try increasing the verbosity level up to 3 (-v 3), and then
rerun the
MET tool.  You should see log messages telling you that it's deriving
wind
speed for you.

Wind direction is a different matter entirely.  The MET tools don't
verify it
directly since it's a "circular" variable.  The current support for
verifying
wind direction in MET is described in section 8.2.6 of the user's
guide.

Hope that helps.

Thanks,
John

On 03/19/2013 09:43 AM, Raby, John W USA CIV via RT wrote:
>
> Tue Mar 19 09:43:00 2013: Request 60694 was acted upon.
> Transaction: Ticket created by john.w.raby2.civ at mail.mil
>         Queue: met_help
>       Subject: Grid-Stat output question
>         Owner: Nobody
>    Requestors: john.w.raby2.civ at mail.mil
>        Status: new
>   Ticket <URL:
https://rt.rap.ucar.edu/rt/Ticket/Display.html?id=60694
> >
>
>
> I have generated the CNT output file from a run where the forecast
grid
> contained UGRD and VGRD but no WIND or WDIR data. The gridded
observation
> data contained UGRD, VGRD, WIND and WDIR data.
>
> My config file specified the fields to be verified as: UGRD, VGRD
and WIND.
>
> How are the error stats contained in the CNT file for WIND
calculated since
> there are no forecast grid values for WIND from which to generate a
matched
> pair difference?
>
> If I were to specify an additional field to be verified as WDIR,
would the
> CNT error stats for WDIR be similarly calculated? Is so, how would
they be
> calculated?
>
> Thanks.
>
> R/
> John
>


Classification: UNCLASSIFIED
Caveats: NONE



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