[Met_help] beginner's point_stat question

John Halley Gotway johnhg at rap.ucar.edu
Fri Feb 13 22:46:23 MST 2009


I looked into your question, and unfortunately, you're right.  Point-Stat
in METv1.1 isn't very smart about which observations it uses.  It uses all
of the observations in the NetCDF point-obs file regardless of valid time.

So for METv1.1, you'd be required to run PB2NC once for each time you'd
like to run Point-Stat.  You'd use PB2NC to filter down to the time window
of observations you'd like to match to your forecasts.

Since releasing METv1.1, we've realized how limited this approach is.  For
METv2.0, we've added "beg_ds" and "end_ds" to the Point-Stat config file,
and have added "-valid_beg" and "-valid_end" as Point-Stat command line
options.  They work the same way as they do in PB2NC.  The "beg_ds" and
"end_ds" are chosen relative to the forecast valid time.  Only the
observations which fall within the user-defined time window are used.

So you're welcome to continue using METv1.1, or if you'd like to try out
METv2.0, you're welcome to use a beta release.  I just need to caution you
that we're still doing development on version 2.0.  So there will be
changes from the beta version to the actual verison that gets released. 
Also, we haven't updated the user's guide yet.

The most recent beta verison is METv2.0beta6.  We used this during the
recent WRF-Tutorial.  If you'd like, you can retrieve it from RAL's
anonymous ftp site:

You'll need to use the verison of the config files that are distributed
with the release.  You can find samples in METv2.0beta6/data/config.

Sorry about the short-sightedness with Point-Stat in METv1.1.  It's a work
in progress.  As you work with the tools, any suggestions for improvment
or feedback is greatly appreciated.


> Hello MET users,
> I'm just getting started with point_stat, and I was wondering how should
> I pair up the OBS with the GRIB FCST files?
> In my first attempt, I gave point_stat a single WRF forecast file valid
> at 21z, along with a whole day's worth of observations converted over
> using pb2nc.   At first glance, it looks like pb2nc took all the
> observations and differences them against the single forecast output
> file.   I suspect this is what happened because I specified a single
> observation site in mask_stations (KHSV), I saw a TOTAL count of 26 in
> the point_stat_....._cnt.txt file.  This seems to suggest that
> point_stat used all observations from the daily netcdf file to verify
> the single forecast time.
> Therefore, should I be merging all the individual hourly WRF GRIB files
> into a single file containing all the times?  Or should I be parsing the
> observations differently when running pb2nc?
> Thanks in advance for the suggestions.
> Jonathan
> ***********************************************************
> Jonathan Case, ENSCO, Inc.
> Aerospace Sciences & Engineering Division
> Short-term Prediction Research and Transition Center
> 320 Sparkman Drive, Room 3062
> Huntsville, AL 35805-1912
> Voice: (256) 961-7504   Fax: (256) 961-7788
> Emails: Jonathan.Case-1 at nasa.gov
>              case.jonathan at ensco.com
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