[ncl-talk] Trying to decode a grib file with limited success

[Andrew Kren - NOAA Federal]

Awesome, thanks!

On Mon, Mar 21, 2022 at 1:57 PM david brown <david.ian.brown at gmail.com>
wrote:

> To  add a bit to Dennis' explanation, you can go to the NCEP page:
>
> https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_table4-2.shtml
>
> which is titled "Parameter Number by Product Discipline and Parameter
> Category".
>
> NCL has an attribute for the variable  VAR_0_1_233_P0_L1_GLC0 called
> "parameter_discipline_and_category"
> with the value "Meteorological products, Moisture".  You will find this
> discipline and category near the top of the NCEP page with a clickable link
> to a page with the
> parameters listed. Near the bottom of that page you will find parameter
> 233 showing its long name: "Snow LIquid Ratio", its units: "kg kg-1" , and
> the name that would
> replace the "VAR_0_1_233" part of the NCL name if NCL's internal GRIB2
> tables were to be updated again: "SNOWLR".
>
> Hope this helps.
>
>
>
> On Mon, Mar 21, 2022 at 9:10 AM Dennis Shea via ncl-talk <
> ncl-talk at mailman.ucar.edu> wrote:
>
>> NCL is correctly unpacking the values.
>>
>> The issue is that the variable's long_name and units are not in the table
>> lookup used by NCL. In a sense, GRIB file contents are a bit of a 'moving
>> target.' The tables must be updated continually. NCL is no longer
>> performing that task.
>>
>> Example:
>>
>> The variable id is 233
>>
>>       float VAR_0_1_233_P0_L1_GLC0 ( ygrid_0, xgrid_0 )
>>          center :       US National Weather Service - NCEP (WMC)
>>          production_status :    Operational products
>>          long_name :    unknown variable name                      <=====
>>          units :
>>  unknown                                                    <=====
>>          _FillValue :   9999
>>          coordinates :  gridlat_0 gridlon_0
>>          grid_type :    Lambert Conformal can be secant or tangent,
>> conical or bipolar
>>          parameter_discipline_and_category :    Meteorological products,
>> Moisture
>>          parameter_template_discipline_category_number :        ( 0, 0,
>> 1, 233 )
>>          level_type :   Ground or water surface
>>          level :         0
>>          forecast_time :        5
>>          forecast_time_units :  hours
>>          initial_time : 03/20/2022 (12:00)
>>
>> warning: Entry (233) not found in code table file
>> /Users/shea/devel/ncl/lib/ncarg/grib2_codetables/ncep/4/4.2.0.1.table
>>
>> You will have to look up grib2_codetables/ncep/4/4.2   or some such
>> thing. Then, manually enter the appropriate information.
>>
>>     X = f->VAR_0_1_233_P0_L1_GLC0
>>     X at long_name = "..."
>>     X at units           = "..."
>>
>> Good luck
>>
>> On Sun, Mar 20, 2022 at 12:08 PM Andrew Kren - NOAA Federal via ncl-talk <
>> ncl-talk at mailman.ucar.edu> wrote:
>>
>>> Hi there,
>>>
>>> I am trying to decode an NBM blend of models grib file but having
>>> trouble determining what the variables are for certain unknown ones.
>>>
>>> When I do an ncl_filedump, I get several listings from the file that are
>>> "unknown variable name". I'm trying to determine the prob snow, sleet, ice,
>>> rain variables but looking at both the ncdump info and the index files, as
>>> well as NOAA VLab is still confusing. The file I am trying to read is
>>> located at this link:
>>>
>>>
>>> https://nomads.ncep.noaa.gov/pub/data/nccf/com/blend/prod/blend.20220320/12/core/blend.t12z.core.f005.co.grib2
>>>
>>> Any help is much appreciated!
>>>
>>> --
>>>
>>> Andrew Kren
>>> Meteorologist
>>> NOAA's National Weather Service
>>> Raleigh Forecast Office
>>> 1005 Capability Drive, Suite 300
>>> Raleigh, North Carolina 27606
>>> voice: 919-326-1035
>>> mailto: andrew.kren at noaa.govhttp://www.weather.gov/rah
>>>
>>>
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>>
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>
>

-- 

Andrew Kren
Meteorologist
NOAA's National Weather Service
Raleigh Forecast Office
1005 Capability Drive, Suite 300
Raleigh, North Carolina 27606
voice: 919-326-1035
mailto: andrew.kren at noaa.govhttp://www.weather.gov/rah
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