[Met_help] point stat & ascii2nc

[John Halley Gotway]

Leela,

Actually, after looking at your ASCII observations, I have a guess as to what's going on.  So you probably don't need to send the GRIB file anyway.

Even though this may not be strictly correct, in your ASCII observations, please try replacing "MSONET" with "ADPSFC" and rerunning ASCII2NC and Point-Stat.  I'm guessing that will fix the problem.

Here's what I believe is going on...  In Point-Stat, observations are typically matched to forecast fields based on pressure level.  So for example, if you're verifying temperature between 800mb and
500mb, it'll look at the pressure level of each observation and match them to the forecast if they fall in that range.  However, that doesn't work for matching observations to forecasts at the
surface.  So in MET, we adopted the method that NCEP's chosen which is to simply match up based on message type.  When verifying fields at the surface (2m temp or 10m winds), Point-Stat only matches
"surface" observations of type ADPSFC or SFCSHP.  Your MSONET observations aren't being matched because they're not being included as a surface observation.  So all observations of type ADPSFC or
SFCSHP are assumed to be at the surface and are matched to forecasts at the surface.

As a user, I'm wondering, what's your opinion?  How would you like to see the matching performed for surface observations?  Is doing it by message type sufficient, or would you like to see us do
something more sophisticated like comparing the elevation of the observation to the elevation at that lat/lon point?

Thanks,
John


Watson.Leela wrote:
> John,
> 
> I cannot send the ARW GRIB file - I keep getting an email back saying
> 'Message Refused: Exceeded Message Size Threshold'. Is there some other
> way that I can get the GRIB file to you? The file size is 16MB. I can
> zip it, but it is still large - 13MB.
> 
> Leela
> 
> -----Original Message-----
> From: John Halley Gotway [mailto:johnhg at rap.ucar.edu] 
> Sent: Tuesday, September 09, 2008 2:41 PM
> To: Watson.Leela
> Cc: met_help at ucar.edu
> Subject: Re: [Met_help] point stat & ascii2nc
> 
> Leela,
> 
> It would probably be easiest if you could send me the sample data that
> you're using.  I'll try running it here to see if I can figure out
> what's going on.
> 
> Please send me the following:
> (1) The ASCII input file to the ASCII2NC tool.
> (2) Your NetCDF output file from ASCII2NC.
> (3) The forecast file containing the 2m temp field from ARW.
> (4) The configuration file that you're using when running the Point-Stat
> tool.
> 
> Thanks,
> John Halley-Gotway
> johnhg at ucar.edu
> 
> Watson.Leela wrote:
>> I am currently trying to use MET to verify 2m temperatures from ARW
>> forecasts with local observation data available in ASCII format. I
>> reformatted my observations to fit the format identified in the MET
>> documentation for the ASCII2NC tool. My observations cover a domain of
>> approximately 20km x 20km and there are only 12 of them. The grid
>> spacing of the ARW output is 1km. When I run the point_stat tool I
>> receive the following message indicating that there are no matching
>> pairs:
>>
>>  
>>
>> Grib Record Index = 11
>>
>> Initialization time = 1201683600
>>
>> Valid time = 1201683600
>>
>> Accumulation time = 0
>>
>> Grib Record (min, max) = (229.37726, 291.74725)
>>
>>  
>>
>> ----------------------------------------
>>
>> Processing 12 observations from 12 PrepBufr messages...
>>
>> For Grib Field TMP at Z2 for observation type MSONET, over region
> FULL,
>> for interpolation method DW_MEAN(3), found 0 pairs.
>>
>>  
>>
>> I also noticed that when I ran the point_stat test script using the
>> sample forecast and ascii data, it also produced similar errors for
> the
>> 10m UGRD and VGRD values:
>>
>>  
>>
>> For Grib Field UGRD at Z10 for observation type ADPUPA, over region
>> DTC165, for interpolation method UW_MEAN(1), found 0 pairs.
>>
>> Etc...
>>
>>  
>>
>> I am confused as to how there can be no matching pairs when the
>> observation point MUST fall between 4 grid points...?? Or maybe I am
>> misunderstanding what the output message is saying. Any help would be
>> appreciated!
>>
>>  
>>
>> Leela Watson
>>
>>  
>>
>> *********************************************************
>>
>> Leela R. Watson, Meteorologist
>>
>> ENSCO, Inc. / Applied Meteorology Unit
>>
>> 1980 N. Atlantic Ave., Suite 230
>>
>> Cocoa Beach, FL 32931
>>
>> Voice: (321) 853-8264
>>
>> Fax: (321) 853-8415
>>
>> Email: watson.leela at ensco.com
>>
>>  
>>
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