[Met_help] Problem with MET and accumulation intervals

John Halley Gotway johnhg at ucar.edu
Tue Nov 17 09:23:32 MST 2009


Actually I think the problem is still in the pcp_comine.cc file.  The unexpected flag values also led to the valid time not being set in the NetCDF file header as one would expect.

Please try using the attached version of pcp_combine.cc instead - and let me know how it goes.


Thomas Schwitalla wrote:
> John,
> now  I have a new problem with the point_stat tool. I only have
> "000000L_20070811_000000V" instead of leading forecast hour in the
> filename. I assume that something has to be edited in the point_stat
> source files...
> Thanks again for your help
> Thomas
> John Halley Gotway schrieb:
>> Thomas,
>> I knew I was forgetting something :)
>> Sorry about that.  Here they are.
>> John
>> Thomas Schwitalla wrote:
>>> John,
>>> John Halley Gotway schrieb:
>>>> Thomas,
>>>> The flags in your GRIB file are set in a way that we've never
>>>> encountered for precipitation.  Where did you get this GRIB file?
>>>> I was able to reproduce the error message you're seeing.  I stepped
>>>> through the call to PCP-Combine using a debugger and found that
>>>> unexpected flag value in the Product Description Section (PDS) of
>>>> the GRIB file.  I ran the file you sent and a sample GRIB file that's
>>>> distributed with MET through the "wgrib" utility to dump out info
>>>> about each record:
>>>> File you sent...  
>>>> 4:26640:d=07080100:APCP:kpds5=61:kpds6=1:kpds7=0:TR=0:P1=4:P2=0:TimeU=13:sfc:1hr
>>>> fcst:NAve=0
>>>> Sample GRIB file...
>>>> 2:31408:d=05080700:APCP:kpds5=61:kpds6=1:kpds7=0:TR=4:P1=3:P2=6:TimeU=1:sfc:3-6hr
>>>> acc:NAve=0
>>>> Looking at these, you can see that the value for the time range
>>>> indicator (TR) is set to 0 in yours, while it's set to 4 in the other
>>>> file.  Now take a look at Table 5 of the GRIB spec:
>>>> http://www.nco.ncep.noaa.gov/pmb/docs/on388/table5.html
>>> thanks for opening my eyes. We used a self written program to convert
>>> MM5 output to GRIB format. Is seems, that during the conversion
>>> something went wrong. We successfully used this tool to convert MM5
>>> output without parameterized convection at 2km resolution, but at 18km
>>> parameterized convection is needed.  I assume this is a problem in our
>>> tool :-(
>>>> A value of 0 is used to simply define a valid time, while a value of 4
>>>> is used to define an accumulation interval between times 1 and 2 (P1
>>>> and P2).  MET expects that the time range indicator will be
>>>> set as an accumulation interval for precipitation.
>>>> Do you think there was an error in defining the flags for this GRIB
>>>> file, or do you really need to be able to read this file as is in
>>>> MET?  If you do need to read it in MET, you'll need to make two
>>>> source code changes:
>>>> (1) Replace the file METv2.0/lib/vx_met_util/read_grib.cc with the
>>>> version that's attached.
>>>> (2) Replace the file METv2.0/src/pcp_combine/pcp_combine.cc with the
>>>> version that's attached.
>>>> Recompile MET with a "make clean" and then rebuild MET.  Please let me
>>>> know the origins of this file and whether we'll need to support it
>>>> directly in MET.
>>> Is it possible, that you send me the code changes as attachment now
>>> (they were missing in your email) ;-) ?
>>>> Hope that helps,
>>>> John
>>> Thanks for opening my eyes,
>>> Thomas
>>>> Thomas Schwitalla wrote:
>>>>> Hi John,
>>>>> currently I have a problem using pcp_combine with a grib dataset for
>>>>> precipitation verification. I get the following error message as an
>>>>> example:
>>>>> "can't find grib code 61 with accumulation of XX hours in grib
>>>>> file". I
>>>>> attached a sample grib file, maybe you can reproduce the error.
>>>>> Best regards from Hohenheim
>>>>> Thomas
>>>>> ------------------------------------------------------------------------
>>>>> _______________________________________________
>>>>> Met_help mailing list
>>>>> Met_help at mailman.ucar.edu
>>>>> http://mailman.ucar.edu/mailman/listinfo/met_help
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