[Met_help] point_stat

John Halley Gotway johnhg at rap.ucar.edu
Wed Apr 29 07:52:40 MDT 2009


I posted a fix for this issue.  Please retrieve the fix from the MET Known Issues page:

I'd suggest following the instructions in the "All Recommended Updates" section.  There are now two bug fixes available and some minor updates to the user's guide, and doing it this way, you'll grab
all of the updates.

Feel free to write with any more questions or problems.


Mark Seefeldt wrote:
> John,
> Thanks for the update.  Please pass around the fix when you have it 
> completed.  The information you provided is valuable as it means that I 
> can start processing the GRIB files for the complete evaluation.
> Mark
> John Halley Gotway wrote:
>> Mark,
>> Thanks for sending the data.  I see what the problem is - there's a
>> bug in the library code that reads the valid time of the GRIB
>> forecast file.  It thinks it 2098 as opposed to 1998.  So Point-Stat 
>> is looking for observation values that are in the time window
>> 20980430 +/- 5400 seconds.  And of course, it doesn't find any!
>> I'm headed out for the day, but I'll put together a fix and send it
>> to you tomorrow.
>> In the meantime, try using the "-valid_beg" and "-valid_end" command
>> line options to manually set the matching time window.  That should
>> get you non-zero matched pairs.
>> Thanks for finding this issue!
>> John
>> Mark Seefeldt wrote:
>>> John,
>>> Thank you for all of the tips and suggestions which you have
>>> provided. I have worked through the different items and I am still
>>> not getting matched pairs when I should be.
>>> I have uploaded the following files to the anonymous ftp: 
>>> phy_sheba-barrow-d01-199805.nc - nc observation file 
>>> phy_sheba-barrow-d01-199805.txt - text observation file 
>>> wppout_d01_1998-04-30_00.grb - GRIB output from using WPPv3.1 
>>> PointStatConfig-phy_sheba - point_stat configuration file
>>> The WRF simulation is for an entire month, centered over Alaska.
>>> The observations are surface pressure, temperature, relative
>>> humidity, downwelling shortwave, and downwelling longwave radiation
>>> for a single site, Barrow, Alaska.
>>> Let me know if you have any additional questions.
>>> Thanks
>>> Mark
>>> John Halley Gotway wrote:
>>>> 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 _______________________________________________ Met_help 
>>>>> mailing list Met_help at mailman.ucar.edu 
>>>>> http://mailman.ucar.edu/mailman/listinfo/met_help
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