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

[david brown]

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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