[Met_help] [rt.rap.ucar.edu #79433] History for MET verification for WRF output

[John Halley Gotway via RT]

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  Initial Request
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Hello, met_help,

I have question about the data format that MET accepted. I have WRF outputs
in netcdf format and RTMA observations in GRIB2 format. I hope to do the
verification and statistic analysis using MET, ensemble-stat tool. For my
understanding, I need to convert the two data sources into common grid
before I put them into MET statistic tools.

My questions is, can MET read WRF outputs into the statistic tool directly?
if so, I only need to re-gridding GRIB data? Do I need to convert GRIB data
into netcdf format before running statistic tool? I know copygb utility can
be used to re-gridding GRIB data. And PCP-combine tool can be used to
generate netcdf files.

Not sure which way to pre-process the data is better so I write this email
asking for some suggestions.

Thank you very much!


-- 
Ying Song, PhD, Post Doctoral Fellow
Department of Earth and Atmospheric Sciences
Saint Louis University

ysong4 at slu.edu


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  Complete Ticket History
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Subject: MET verification for WRF output
From: John Halley Gotway
Time: Tue Feb 14 12:11:22 2017

Ying,

I see you have questions about verifying WRF output files and
regridding.

Unfortunately, MET does not read the NetCDF output of WRF directly.
There
are two main issues here.  First, wrfout files are on hybrid pressure
levels in the vertical, and second, some of the output variables are
defined on a staggered grid.  Some sort of post-processing is required
prior to verifying this data in MET.

You have two options.  The wrf_interp utility is reads WRF-ARW output
and
converts from hybrid vertical levels to pressure levels.  MET is able
to
read the output of wrf_interp, but only variables defined on the
non-staggered dimension.  So temperatures are fine, but not winds.

The second option is running the unified postprocessor (UPP).  It
reads
WRF-ARW and WRF-NMM, interpolates to pressure levels, computes many
derived
variables, and can interpolate to whatever output grid you'd like.
It's
output is GRIB1 or GRIB2 which MET can easily read.  For these
reasons, we
recommend using UPP instead of wrf_interp.

On to regridding... As of MET version 5.2, we adding support for
automated
regridding within the MET tools themselves.  You of course still have
option of using copygb to regrid GRIB1 data or wgrib2 to regrid GRIB2
data.  But you can also use the "regrid" section within the MET config
files to specify how you'd like data placed on a common grid prior to
verification.  In addition, met-5.2 includes a stand-alone utility
called
regrid_data_plane which reads one or more fields from an input file
and
regrids it to whatever domain you specify.

Hope that helps clarify the options.

Thanks,
John Halley Gotway
met_help at ucar.edu



On Mon, Feb 13, 2017 at 3:22 PM, Ying Song via RT <met_help at ucar.edu>
wrote:

>
> Mon Feb 13 15:22:02 2017: Request 79433 was acted upon.
> Transaction: Ticket created by ysong4 at slu.edu
>        Queue: met_help
>      Subject: MET verification for WRF output
>        Owner: Nobody
>   Requestors: ysong4 at slu.edu
>       Status: new
>  Ticket <URL:
https://rt.rap.ucar.edu/rt/Ticket/Display.html?id=79433 >
>
>
> Hello, met_help,
>
> I have question about the data format that MET accepted. I have WRF
outputs
> in netcdf format and RTMA observations in GRIB2 format. I hope to do
the
> verification and statistic analysis using MET, ensemble-stat tool.
For my
> understanding, I need to convert the two data sources into common
grid
> before I put them into MET statistic tools.
>
> My questions is, can MET read WRF outputs into the statistic tool
directly?
> if so, I only need to re-gridding GRIB data? Do I need to convert
GRIB data
> into netcdf format before running statistic tool? I know copygb
utility can
> be used to re-gridding GRIB data. And PCP-combine tool can be used
to
> generate netcdf files.
>
> Not sure which way to pre-process the data is better so I write this
email
> asking for some suggestions.
>
> Thank you very much!
>
>
> --
> Ying Song, PhD, Post Doctoral Fellow
> Department of Earth and Atmospheric Sciences
> Saint Louis University
>
> ysong4 at slu.edu
>
>

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