[Met_help] met and WRF/ARW

[John Halley Gotway]

Julien,

Yes, we highly recommend running your WRF output through WPP prior to using it in MET.  Running it through WPP does three things:

(1) Interpolates in the horizontal from the staggered model grid to a regular grid.
(2) Interpolates in the vertical from eta levels to pressure levels.  The MET Point-Stat tool does matching in the vertical using pressure levels, not eta levels, since observations are typically
reported at pressure levels.
(3) Derives several fields, including temperature from the ARW model output.

Try switching your WRF output format back to NetCDF and rerunning it through WPP.  I mentioned this to the primary WPP support person here, and she guessed that since you're running ARW, you probably
have multiple output times in each NetCDF output file.  Because of that, you'll need to run the WPPV3.1/scripts/run_wrfpost_frames script.  That will read multiple times from the ARW NetCDF files and
write them out to separate GRIB output files.

Please give that a shot, and if you continue to experience trouble running WPP, send an email to wrfhelp at ucar.edu.

Thanks, and once you get up and running, let us know if any more questions arise in your use of MET.

John Halley Gotway
johnhg at ucar.edu

Julien Pergaud wrote:
> Hello
> 
> I have some questions abous the use of MET with the version ARW of WRF.
> First, as explained in the tutorial, i have used WPP to transform nectdf output 
> in grib.
> But, if the first files (first time of the simulation) was tranformed in grib 
> without problem, it was not the case for other files (other times).
> So, i have decided to use the possibility of WRF/ARW to create as output grib 
> files directly.
> When i want to use the capability of MET to deal with UPA data, i meet some 
> problems.
> First, in grib file obtained directly from WRF/ARW, levels are defined as ETA 
> levels and not pressure levels.
>   - How can i read eta levels with MET? Is it possible?
>   - TMP can be extract at different level using LNNN or RNNN. Are L and R linked 
> to eta levels. For example, L1.2 doesn't run while L2.5 runs.
>    - This remark is linked to the previous. Temperature is an output variable of 
> WRF only for 2m level. WRF provides potentiel temperature at the different 
> vertical levels and not TMP.
>      Is MET able to compute temperature from the different variable of WRF 
> (potential temperature and pressure)? If not what is TMP/L2.5
>      if i put POT as a variable name in the PointStat config file, MET 
> 
> I have checked the only grib file coming from WPP and this last one contains TMP 
> at different vertical pressure levels.  So WPP seems to compute temperature from 
> potential temperature.
> Do you think it's better to use WPP. If yes, how can i solve my problem with WPP.
> Thank you in advance for your answer.
> 
> Julien  
> -- 
> 
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