Introduction

This document briefly describes the NCEPLIBS-g2tmpl library.

GRIB2 Tables/Templates

NCO Provides documentation on WMO GRIB2 at https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/

WMO's GRIB2 specification "FM 92-XII GRIB - General Regularly-distributed Information in Binary Form" contains descriptions of each template and code table information. This document can be found at https://codes.wmo.int/grib2/_codeflag (PDF and MSWord formats are available).

Editing Parameters in the GRIB2 Tables

GRIB2 - TABLE 4.2-0-0 PARAMETERS FOR DISCIPLINE 0 CATEGORY 0

GRIB2 parameter table for all disciplines and categories and parameter. These fields are in order as below:

grib2_disc#  grib2_cat#  grib2_param# local_flg#     Mnemonic

Where:

grib2_disc# grib2_discipline
grib2_cat# grib2_category
grib2_param# grib2_parameter_number WMO parameters have values ranging from 0 to 191 and NCEP local table parameters have values from 192a to 254 the parameter value 255 is a missing or undefined.
local_flg# grib2_table_flag information (0 for the parameter from the WMO table and 1 for the parameter from the NCEP local table)
Mnemonic grib2_NCEP_mnemonic (locally defined at NCEP).

Example

An entry of paramter TEMPERATURE in grib2 table 4.2

grib2_disc#  grib2_cat#  grib2_param# local_flg#     Mnemonic
    0             0           0            0            TMP

Where:

grib2_disc# is DISCIPLINE
grib2_cat# is CATEGORY
grib2_param# is PARAMETER NUMBER
local_flg# is 0 = WMO table is 1 = locally defined at NCEP
Mnemonic is Mnemonic of parameter

After you added parameters, You need to run executable program sort_params_grib2_tbl to write out a "params_grib2_tbl_new" SORTED file in a format suitable for subsequent reading via the open_and_read_4dot2() function.

Note: DO NOT use UNIX command "sort" to sort params_grib2_tbl_new file.

The procedures are following:

Save the original file

    cp params_grib2_tbl_new  params_grib2_tbl_new.save

edit params_grib2_tbl_new file
add new parameter example:
```
           0  19    37   0 ICESEV
```
run the sort_params_grib2_tbl manually to write output file which it will be sorted.

Adding New Generating Process ID or Model ID PDT in GRIB2 tables

The following variables are often requested by developers: parameters, model id or new grid id to add to NCEPGRIB2 tables. Example:

parameter category (see Code table 4.1)
parameter number (see Code table 4.2)
generating process identified (see Code ON388 Table A)
fixed surface level (see Code Table 4.5)
derived forecast (see Code Table 4.7)
New grid ID - example: Latitude/Longitude grid (See Template 3.0)

Developer will provide the following information for new variable: definition (i.e.,meaning of parameter) unit, GRIB2 discipline and category which this variable should be belongs to in GRIB2 tables.

Then, We will check for new variable in NCEP GRIB2 tables before we define new variable in NCEP GRIB2 tables to avoid a duplication. If the new variables will be used for exchange between UKMet or ECMWF. In this case, we need to request approval from WMO. We will ask Jeff Ator (Who is our WMO representative at EMC) to submit this request to WMO. This request usually takes weeks. Otherwise, We can define it as in NCEP local use.

For example, parameter “TMP” has defined in discipline 0, category 0 (Meteorological products,Temperature category) and parameter number is 0 (see Table 4.2-0-0) as an WMO official and parameter number is above 192 to 254 are NCEP local define.

After we have added a new variable in WMO NCEP GRIB2 tables, we need to update the G2TMP library. We need to check out code of the g2tmpl at NOAA-EMC github.com

             export dir=` pwd `
             mkdir -p  g2tmpl
             cd g2tmpl
             git clone   git@g.nosp@m.ithu.nosp@m.b.com:NOAA-EMC/NCEPLIBS-g2tmpl.git
 cd  NCEPLIBS-g2tmpl
 git  checkout   -b   g2tmpl_v1.6.0
            cd g2tmpl_v1.6.0
            cd src

#

Adding New Parameter in G2TMPL library

Edit the params_grib2_tbl_new.text file to add new variable We need to save a copy of params_grib2_tbl_new.tex file and params_grib2_tbl_org file before We begin to add new variables. The steps are below:

cp params_grib2_tbl_new.text params_grib2_tbl_new.text_org
cp params_grib2_tbl_new params_grib2_tbl_new_org

vi params_grib2_tbl_new.text

Example:  Temperature  ⇒  it is in discipline 0 category 0 and parameter 0

* WMO parameters have values ranging from 0 to 191 - set to 0
* NCEP local table parameters have values from 192 to 254 - set to 1
* parameter value 255 is a missing or undefined

! GRIB2 - TABLE 4.2-0-0 PARAMETERS FOR DISCIPLINE 0 CATEGORY 0
column  1    ||   Column 2   ||  Parameter   ||   WMO or local  || Abbreviation
     0                    0                           0                         0                    TMP
!  NCEP Local use
     0                    0                    192                       1                   SNOHF

Remember to add a comment line when we add new variable

Example:

!  Added more parameters on 02/25/2021
      0                 0                      205                         1                  ELMELT

Save the params_grib2_tbl_new.text file
Copy params_grib2_tbl_new.text file to params_grib2_tbl_new file cp params_grib2_tbl_new.text params_grib2_tbl_new
When we completed adding variables, we need to run the program sort_params_grib2_tbl to sort the params_grib2_tbl_new file with a format suitable for subsequent reading. (if the executable has not been built, we will run script to build it) -Build executable ===> sort_params_grib2_tbl Run script build_sort_grib2_tbl.sh -Run it to sort the params_grib2_tbl_new file Sort_params_grib2_tbl ==> The output file is: params_grib2_tbl_new file
We will give these two files: params_grib2_tbl_new.text and params_grib2_tbl_new to developer for testing and UPP (code manager is Wen).

New Generating Process ID (see Code ON388 Table A) or Product Definition Template.

(see PDT at https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_table4-0.shtml) We need to modify the following files in g2tmpl library:

g2sec4_temp11.f90 (It is for PDT 4.11)
g2sec4_temp12.f90 (It is for PDT 4.12)
g2sec4_temp1.f90 (It is for PDT 4.1)
Grib2_all_tables_module.f90

After you have received a confirm from developer, You can submit a PR and nceplibs team will implement g2tmpl v?.?.? in hpc-stack and delivery code to NCO to implement on WCOSS2. NCO requires to have release notes with delivery code form An example of release note (g2tmpl v1.6.0) for delivery code form https://docs.google.com/document/d/1VK3j0K0CXRxaP7ZW-uJuyGKosVVAuIOkBBIafY2tzW0/edit -Guidance for Adding a new variable to the UPP code (Please contact Wen Meng) https://docs.google.com/document/d/1r2BQtAI33S_zCDh6Ko-aFW0kO79MYILspW31Bw4zE60/edit

Maintaining NCEP WMO GRIB2 DOCUMENTATION and Update GRIB2 library

The NCEP WMO grib2 document is on NCO RZDM web site: https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/ WMO updates documentation grib2 tables every 6 months (May and November). The WMO documents are in the machine-readable format (e.g. XML, CVS). Because WMO does not have resources to keep the WMO document in PDF format since WMO version 25.0 (Released date - May 06, 2020). The WMO latest version is at this link: https://community.wmo.int/activity-areas/wis/latest-version

I have updated (8/15/2022) the NCEP WMO GRIB2 documentation and ON-388 to the latest version 29.0 - WMO released date May 20, 2022.

This is an operational NCO Web-site. Please be careful of using this web-site (e.g., remove files,...). NCO is creating a group account for EMC to access on NCORZDM. The location of files (shtml) are following:

Document for GRIB2 /home/people/nco/nwprod/pmb/docs/grib2/grib2_doc Example: Adding new variable “Simulated Brightness Temperature for Himawari-8, Band-16” in grib2 4-3-192 table (grib2_table4-2-3-192.shtml). vi grib2_table4-2-3-192.shtml We will add “Simulated Brightness Temperature for Himawari-8, Band-16” in grib2 table 4.2.3.192 and assign it to next value of parameter number which we already assigned to it as above in steps. See grib2_table4-2-3-192.shtml at this link: https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_table4-2-3-192.shtml
Document for GRIB1 /home/people/nco/nwprod/pmb/docs/on388
Source code /home/people/nco/nwprod/pmb/codes/GRIB2 (This site has been redirected to GitHub)
Updated existing grib2 tables or add new grib2 (GDT/PDT) in G2 and G2C library We need to modify the following files in G2 or G2C library:

gridtemplates.F90 This file updates “Grid Definition Template”s used in Section 3
pdstemplates.F90 This file updates “Product Definition Templates” used in Section 4
params.F90 This file updates the available parameters in GRIB2 tables.
New file as needed (e.g., new compression, new feature, …)