[ncl-talk] A potential bug when reading precipitation from GFS data

[Kyle Griffin]

This is not a bug to my knowledge, GFS files have been this way for quite
some years. All parameterized fields don't exist in the F000 files, exist
with _acc or _avg at F006, and with _acc6h or _avg6h at F012 and beyond. In
my decoding, I can see this is readily true with cloud cover variables and
outgoing longwave radiation variables in addition to precipitation. It's
important to note that precip in grids beyond 6 hours can be accumulation
of different kinds - either over the latest 6 hours or over all hours
combined over the entirety of the times since the initialization of the
model run. It is important to look at the documentation and descriptions -
these are all provided nicely within the GRIB2 file attributes as well, if
you look without grep commands.

It is *crucial* to understand your data - if you can't tell the difference
between the fields, you need to stop and look more closely. See below,
first text is from forecast hour 6 and second from forecast hour 36.

      float APCP_P8_L1_GLL0_acc ( lat_0, lon_0 )

         center : US National Weather Service - NCEP (WMC)

         production_status : Operational products

         long_name : Total precipitation

         units : kg m-2

         _FillValue : 1e+20

         grid_type : Latitude/longitude

         parameter_discipline_and_category : Meteorological products,
Moisture

         parameter_template_discipline_category_number : ( 8, 0, 1, 8 )

         level_type : Ground or water surface

         level : 0

         type_of_statistical_processing : Accumulation

      *   statistical_process_duration : initial time to forecast time*

         forecast_time : 6

         forecast_time_units : hours

         initial_time : 08/29/2014 (00:00)


      float APCP_P8_L1_GLL0_acc6h ( lat_0, lon_0 )

         center : US National Weather Service - NCEP (WMC)

         production_status : Operational products

         long_name : Total precipitation

         units : kg m-2

         _FillValue : 1e+20

         grid_type : Latitude/longitude

         parameter_discipline_and_category : Meteorological products,
Moisture

         parameter_template_discipline_category_number : ( 8, 0, 1, 8 )

         level_type : Ground or water surface

         level : 0

         type_of_statistical_processing : Accumulation

       *  statistical_process_duration : 6 hours (ending at forecast time)*

         forecast_time : 36

         forecast_time_units : hours

         initial_time : 08/29/2014 (00:00)


Kyle

----------------------------------------
Kyle S. Griffin
Department of Atmospheric and Oceanic Sciences
University of Wisconsin - Madison
Room 1421
1225 W Dayton St, Madison, WI 53706
Email: ksgriffin2 at wisc.edu


On Thu, Aug 28, 2014 at 10:00 PM, Rabah Hachelaf <hachelaf at sca.uqam.ca>
wrote:

> Files can be downloaded simply by these links :
>
>
> ftp://ftpprd.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.2014082800/gfs.t00z.pgrb2f06
>
> ftp://ftpprd.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.2014082800/gfs.t00z.pgrb2f12
>
> ftp://ftpprd.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.2014082800/gfs.t00z.pgrb2f18
>
>
> 2014-08-28 22:50 GMT-04:00 Dennis Shea <shea at ucar.edu>:
>
>> This is offline.
>>
>> Send the files to
>>
>> ftp ftp.cgd.ucar.edu
>> anonymous
>> your_email
>> cd incoming
>> put gfs.t00z.pgrb2f06.grib2
>> put gfs.t00z.pgrb2f12.grib2
>> quit
>>
>> Notify me *after* successful transfer of the files.
>>
>> ===
>> Also, whenever you suspect a bug, please include the version of NCL you
>> are using.
>>
>> %> ncl -V
>>
>>
>> Regards
>>
>>
>>
>>
>>
>>
>>  On Thu, Aug 28, 2014 at 8:42 PM, Rabah Hachelaf <hachelaf at sca.uqam.ca>
>> wrote:
>>
>>> Hi all,
>>>
>>> When reading precipitation from GFS 0.5 deg data precipiation variables
>>> change names between 6h forecast and other hours like this :
>>>
>>>  ncl_filedump gfs_data/gfs.t00z.pgrb2f06.grib2 | grep "AP"
>>>       float CAPE_P0_L1_GLL0 ( lat_0, lon_0 )
>>>       float CAPE_P0_2L108_GLL0 ( lv_SPDL11, lat_0, lon_0 )
>>>       float APCP_P8_L1_GLL0_acc ( lat_0, lon_0 )
>>>
>>> ncl_filedump gfs_data/gfs.t00z.pgrb2f12.grib2 | grep "AP"
>>>       float CAPE_P0_L1_GLL0 ( lat_0, lon_0 )
>>>       float CAPE_P0_2L108_GLL0 ( lv_SPDL11, lat_0, lon_0 )
>>>       float APCP_P8_L1_GLL0_acc*6h* ( lat_0, lon_0 )
>>>
>>> I am not sure if this is a bug or there is an other way to read all
>>> forecast hours with the same variable name.
>>>
>>> Rabah
>>> --
>>> ------------------------------
>>> Cordialement,
>>> Best regards,
>>> Rabah Hachelaf
>>>
>>>
>>> _______________________________________________
>>> ncl-talk mailing list
>>> List instructions, subscriber options, unsubscribe:
>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>
>>>
>>
>
>
> --
> ------------------------------
> Cordialement,
> Best regards,
> Rabah Hachelaf
>
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> ncl-talk mailing list
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> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>
>
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