[ncl-talk] Confusion on GFS files in GRIB2

Lyndz olagueralyndonmark429 at gmail.com
Mon Mar 8 21:10:16 MST 2021 

Hello,

In addition to Sir Dennis' reply.

*[1] *If you want to plot the surface temperature, use the
*TMP_P0_L103_GLL0*


*Variable: temp*

*Type: float*

*Total Size: 4152960 bytes*

*            1038240 values*

*Number of Dimensions: 2*

*Dimensions and sizes: [lat_0 | 721] x [lon_0 | 1440]*

*Coordinates: *

*            lat_0: [90..-90]*

*            lon_0: [ 0..359.75]*

*Number Of Attributes: 14*

*  initial_time : 11/10/2020 (00:00)*

*  forecast_time_units : hours*

*  forecast_time : 3*

*  level_type : Specified height level above ground (m)*

*  parameter_template_discipline_category_number : ( 0, 0, 0, 0 )*

*  parameter_discipline_and_category : Meteorological products, Temperature*

*  grid_type : Latitude/longitude*

*  units : K*

*  long_name : Temperature*

*  production_status : Operational products*

*  center : US National Weather Service - NCEP (WMC)*

*  lv_HTGL2 : 2*

*  _FillValue : 1e+20*

*  level : 0*



*[2] *Check this simple explanation from David Brown's reply in one of the
posts here:


https://mailman.ucar.edu/pipermail/ncl-talk/2015-December/004772.html



*[3] *Have a look at NCL's sample scripts for plotting GRIB2 files here:


http://www.ncl.ucar.edu/Training/Workshops/UMaine/Scripts/Plymouth/




Sincerely,


Lyndz



On Tue, Mar 9, 2021 at 5:19 AM Dennis Shea <shea at ucar.edu> wrote:

> [1] Please: Always include the version of NCL you are using.
>
> %> ncl -V
>
> The most recent version is 6.6.2
>
> [2] Before processing, you can examine a GRIB file's contents via:
>
> %> *ncl_filedump* gfs.t00z.pgrb2.0p25.f001.grb | less
>
> Do you see a variable named "TMP_P0_L102_GLL0" ?
>
> [3]
>
> grib_file = "gfs.t00z.pgrb2.0p25.f001"   + ".grb"
> fin = addfile(grib_file, "r")
> varnames = getfilevarnames(fin)
> print(varnames)
>
> The output you included shows only vertical dimension variables:  lv_*
> (0)     lv_DBLL14_l1
> (1)     lv_DBLL14_l0
> (2)     lv_ISBL13
>          ......SNIP ......
> (15)    lv_HTGL2
> (16)    lv_AMSL1
> (17)    lv_ISBL0
>
>
> Then, NCL tells you that the variable *TMP_P0_L102_GLL0* *is not in the
> grib file *
>
>
>
> On Mon, Mar 8, 2021 at 1:35 PM dr.hieronymus--- via ncl-talk <
> ncl-talk at mailman.ucar.edu> wrote:
>
>> Hi,
>>
>> Regarding the GFS files, I have written to NCEP. Thanks, that was a good
>> idea.
>>
>> When using following code:
>>
>> ;;; load ncl scripts/files
>> load "/usr/lib/ncarg/nclscripts/csm/gsn_code.ncl"
>> load "/usr/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
>> load "/usr/lib/ncarg/nclscripts/csm/contributed.ncl"
>>
>> begin
>>
>> ;;; read data from grib file
>> grib_file = "gfs.t00z.pgrb2.0p25.f001"
>> fin = addfile(grib_file, "r")
>> varnames = getfilevarnames(fin)
>>
>> print(varnames)
>> printVarSummary(fin->TMP_P0_L102_GLL0)
>>
>> ;;; get variables: level, variable, longitude, latitude
>> ;t2m = fin->TMP_P0_L102_GLL0(:,:)
>> ;lon = fin->lon
>> ;lat = fin->lat
>>
>> ;;; convert to degrees
>> ;t2m = t2m-273.15
>>
>> end
>>
>> I get the following error message:
>>
>> warning:NclGRIB2: APCP_P8_L1 contains records that NCL cannot currently
>> differentiate. One or more records will be ignored.
>> warning:NclGRIB2: ACPCP_P8_L1 contains records that NCL cannot currently
>> differentiate. One or more records will be ignored.
>> fatal:GdsCEGrid: Invalid grid detected
>> fatal:NclGRIB2: Couldn't handle dimension information returned by grid
>> decoding
>> fatal:NclGRIB2: Deleting reference to parameter because of decoding
>> error
>> fatal:GdsCEGrid: Invalid grid detected
>> fatal:NclGRIB2: Couldn't handle dimension information returned by grid
>> decoding
>> fatal:NclGRIB2: Deleting reference to parameter because of decoding
>> error
>> ...
>> ...
>> ...
>> fatal:GdsCEGrid: Invalid grid detected
>> fatal:NclGRIB2: Couldn't handle dimension information returned by grid
>> decoding
>> fatal:NclGRIB2: Deleting reference to parameter because of decoding
>> error
>> fatal:GdsCEGrid: Invalid grid detected
>> fatal:NclGRIB2: Couldn't handle dimension information returned by grid
>> decoding
>> fatal:NclGRIB2: Deleting reference to parameter because of decoding
>> error
>>
>>
>> Variable: varnames
>> Type: string
>> Total Size: 144 bytes
>>              18 values
>> Number of Dimensions: 1
>> Dimensions and sizes:   [18]
>> Coordinates:
>> (0)     lv_DBLL14_l1
>> (1)     lv_DBLL14_l0
>> (2)     lv_ISBL13
>> (3)     lv_ISBL12
>> (4)     lv_SPDL11_l1
>> (5)     lv_SPDL11_l0
>> (6)     lv_ISBL10
>> (7)     lv_ISBL9
>> (8)     lv_HTGL8
>> (9)     lv_ISBL7
>> (10)    lv_SIGL6_l1
>> (11)    lv_SIGL6_l0
>> (12)    lv_ISBL5
>> (13)    lv_HTGL4
>> (14)    lv_PVL3
>> (15)    lv_HTGL2
>> (16)    lv_AMSL1
>> (17)    lv_ISBL0
>> fatal:["Execute.c":6397]:variable (TMP_P0_L102_GLL0) is not in file
>> (fin)
>> fatal:["Execute.c":8640]:Execute: Error occurred at or near line 14 in
>> file temperature_tmp.ncl
>>
>> Do I understand correctly that ncl has detected an invalid grid? Why?
>>
>> Thanks.
>>
>>
>>
>> Am 08.03.2021 16:44 schrieb Lyndz:
>> > Hi,
>> >
>> > I'm not sure if this is an ncl question. You should have directed your
>> > questions to the ncep help page (
>> > https://www.ncep.noaa.gov/mail_dataquestions/)
>> >
>> > *[1] *As far as I know, the .anl files are analyses files and were
>> > already
>> > assimilated with observations.
>> >
>> > *[2]* If you want to use the forecast, then use the files with the
>> > following format (
>> >
>> https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.20210308/12/
>> ):
>> >
>> > gfs.t12z.pgrb2.0p25.f000
>> > <
>> https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.20210308/12/gfs.t12z.pgrb2.0p25.f000
>> >
>> >
>> > gfs.t12z.pgrb2.0p25.f001
>> > <
>> https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.20210308/12/gfs.t12z.pgrb2.0p25.f001
>> >
>> >
>> > etc..
>> >
>> > No need to download the other files!
>> >
>> > ncl_filedump gfs.t12z.pgrb2.0p25.f000.grb will give you the contents
>> > of the file.
>> >
>> > If you want temperature, then look for the keyword "Temperature". This
>> > will give u information about the variables such as below:
>> >
>> > float TMP_P0_L102_GLL0 ( lv_AMSL1, lat_0, lon_0 )
>> >
>> >          center :       US National Weather Service - NCEP (WMC)
>> >
>> >          production_status :    Operational products
>> >
>> >          long_name :    Temperature
>> >
>> >          units :        K
>> >
>> >          _FillValue :   1e+20
>> >
>> >          grid_type :    Latitude/longitude
>> >
>> >          parameter_discipline_and_category :    Meteorological
>> > products, Temperature
>> >
>> >          parameter_template_discipline_category_number :        ( 0, 0,
>> > 0, 0 )
>> >
>> >          level_type :   Specific altitude above mean sea level (m)
>> >
>> >          forecast_time :        72
>> >
>> >          forecast_time_units :  hours
>> >
>> >          initial_time : 03/08/2021 (00:00)
>> >
>> > The variable name is the same for other GFS files, regardless of
>> > resolution.
>> >
>> > *[3]* For documentation, check this:
>> >
>> https://www.emc.ncep.noaa.gov/emc/pages/numerical_forecast_systems/gfs/documentation.php
>> >
>> > *[4] *The files are archived in rda.ucar.edu. For the 25km GFS, for
>> > example, see this link:
>> >
>> > https://rda.ucar.edu/datasets/ds084.1/#!docs
>> >
>> >
>> >
>> > Hope this helps.
>> >
>> > --Lyndz
>> >
>> >
>> >
>> > On Mon, Mar 8, 2021 at 8:05 PM dr.hieronymus--- via ncl-talk <
>> > ncl-talk at mailman.ucar.edu> wrote:
>> >
>> >> Hello,
>> >>
>> >> I am trying to dig through GFS files in GRIB2 format on NCEP's FTP
>> >> server (https://www.nco.ncep.noaa.gov/pmb/products/gfs/).
>> >>
>> >> Unfortunately, it is not very easy to get a proper overview.
>> >> Therefore,
>> >> my first question is whether there is documentation somewhere that
>> >> describes the different formats/variants in detail.
>> >>
>> >> What one quickly notice and easy understand is that the GFS files are
>> >> available in different resolutions (0.25°, 0.50°, 1.00°) and each GFS
>> >> file is described by an index file. The GFS files with 0.25°
>> >> resolution
>> >> have an hourly granularity and the GFS files with 0.50° and 1.00°
>> >> resolution have a three-hourly granularity.
>> >>
>> >> Then, there are the .anl and .f000 GFS files. I don't understand the
>> >> difference between .anl and .f000. Is .f000 not a forecast?
>> >> Furthermore,
>> >> I noticed that the index files are different regarding .f000 and
>> >> .f001-384 (0.25°) and .f000 and .f003-384 (0.50°, 1.00°).
>> >>
>> >> What also confuses me are the different GFS files, namely pgrb2,
>> >> pgrb2b,
>> >> pgrb2full and sfluxgrbfFFF. What are the differences exactly?
>> >> According
>> >> to the corresponding index files, the same physical variables are
>> >> available in all different GFS files. Do these variables always have
>> >> the
>> >> same values in all GFS files? Doesn't it matter which file I use
>> >> when
>> >> I have decided on a resolution?
>> >>
>> >> I am actually only interested in the temperature 2 meters above the
>> >> ground. Which file should I simply use?
>> >>
>> >> In addition, I also wanted to know if the initial values for each
>> >> model
>> >> run (00, 06, 12, 18) are published somewhere.
>> >>
>> >> Thank you in advance for your help.
>> >> _______________________________________________
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