[ncl-talk] A potential bug when reading precipitation from GFS data
David Brown
dbrown at ucar.edu
Fri Aug 29 00:47:48 MDT 2014
Kyle is correct about this issue. However, I would also like to point out
that there is a setfileoption call that can be used to remove the time
period suffix if you really need to. Put
setfileoption("grb","TimePeriodSuffix",False)
prior to the 'addfile' call.
This will have the effect of changing variables with names like
APCP_P8_L1_GLL0_acc6h
into
APCP_P8_L1_GLL0_acc
However, this can cause confusion if, as Kyle notes, there happen to be
separate statistical variables with different time periods.
So do this at your own risk.
-dave
On Thu, Aug 28, 2014 at 9:45 PM, Kyle Griffin <ksgriffin2 at wisc.edu> wrote:
> 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:
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>>>>
>>>>
>>>
>>
>>
>> --
>> ------------------------------
>> Cordialement,
>> Best regards,
>> Rabah Hachelaf
>>
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>>
>
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