[Met_help] point_stat

[John Halley Gotway]

Mark,

Let me make a few comments about this.

First, depending on how you configure Point-Stat, getting 0 matched pairs for certain combinations of variables/message type may be fine.  For example, if you configure Point-Stat to verify
Temperature at 2-meters above the surface (TMP/Z2) and at 500mb (TMP/P500) using message types of ADPSFC (surface obs) and APDUPA (upper air obs), you would actually expect to get 0 matched pairs for
TMP/Z2 vs APDUPA and 0 matched pairs for TMP/P500 vs ADPSFC.  So sometimes having 0 matched pairs is fine.

However, if you're getting 0 matched pairs when you expect that you should actually be finding some, here's what I'd ask myself:

- Am I applying some masking region (a grid or a polyline) that is perhaps not working like I expect?  Try rerunning with the masking grid set to FULL to verify over the whole domain.

- Does my forecast field contain valid data?  Clearly Point-Stat is finding the fields you'd like to verify, otherwise it'd error out.  But if what it's finding contains only bad data, it won't find
any matched pairs.  Can you view the forecast field with some other tool to check that the field contains valid data?  For NetCDF format, use ncview.  For GRIB, "wgrib -V" will tell you the min/max
data values.  Or you could view the GRIB file using NCL or IDV.  Or you could run it through the MET-MODE tool and look at the output plot.

- Do I have my valid times correct?  Am I using observations that are valid around the same time that my forecast file is valid?  In the Point-Stat config file, you could set the "beg_ds" and "end_ds"
values to define a VERY large time window to see if you can get some matched pairs.

- Lastly, do the observations I'm using not match my forecast for some other reason?  For example, are the message types for the observations correct?  You could try doing an ncdump to see what
message types are in your point observation file (ncdump -v hdr_typ file_name.nc | sort -u).  Or are the observations not matching for some other reason?  This would be the most difficult to determine!

Hopefully that'll help you figure out what's going on with your data. I'd suggest "opening" things up as much as possible (mask grid = FULL and set beg_ds/end_ds very large) to try to get non-zero
matched pairs, and go from there.

If you're still having problems after trying these things, feel free to send me some sample files, and I could take a look to see what going on.  You'd need to send me:
(1) Forecast file input for Point-Stat.
(2) Observation file input for Point-Stat.
(3) Configuration file input for Point-Stat.
And you could post those files to RAL's anonymous ftp site:
ftp ftp.rap.ucar.edu
username = anonymous
password = "your email address"
cd incoming/irap/johnhg
put "those 3 files"
bye (to exit ftp)

Thanks and good luck,
John


Mark Seefeldt wrote:
> I am working on a model evaluation using point_stat in MET.  As it 
> processes I am getting 0 pairs matched, therefore no statistics.  Is 
> there a preferred method to identify if it is the observation file, the 
> forecast file, or the configuration file where the error resides 
> resulting in the lack of matched obs/fcst values?  I am at a loss as to 
> what is wrong in my setup which is preventing the obs/fcst pairs to be 
> matched and to create the output.
> 
> Thanks
> 
> Mark
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