Pre-built ICON Grids and ExtPar Data

A list of grid files have been pre-built for the ICON model together with the corresponding reduced radiation grids and the external parameters.

Where are the grid files stored?

The primary storage location for ICON grids is
- mistral.dkrz.de:/pool/data/ICON/grids/public
Every 24h the contents of the primary storage directory are mirrored to DWD's HPC.
Every 24h the contents of the primary storage directory are mirrored to a public web site
- http://icon-downloads.mpimet.mpg.de/

Every grid file consists of a NetCDF file and a GPG signature file (http://de.wikipedia.org/wiki/GNU_Privacy_Guard).
The signature file makes sure that a grid file is complete and verifies the authorship.

Grid file nomenclature

The grids are identified by

a centre number
a subcentre number
a numberOfGridUsed which is simply an integer number, increased by one with every new "official" grid.

The grid files and the external parameter files are named accordingly, e.g.,

icon_grid_0001_RxxByy_G.nc

icon_extpar_0001_RxxByy_G.nc

icon_grid_0001_RxxByy_O.nc

where the name components are as follows:

icon	_	grid	_	0001	_	R	02	B	06	_	R.nc (radiation/reduced)
		extpar	_	0002	_	R	03	B	07	_	G.nc (global)
icon	_	grid	_	0001	_	R	02	B	06	_	O.nc (ocean only)
				...			...		...

The numberOfGridUsed parameter is part of the file name (0001, ...) and makes this file name unique.

How can I find a specific grid file?

A table lookup is required to find the actual file name to which a set of these parameters corresponds. This "table file" is located in "xml/dwd_grids.xml" (the table file itself is under version control: git@git.mpimet.mpg.de:icon_grid_table.git). There exists a grid access tool

icon_grid_get

to simplify matters.

This tool processes the XML file and returns the grid file name.
It provides a unified access to the "official" set of ICON grids,
- stored locally in the user's home directory
- stored locally in a system-wide directory (environment variable ICON_GRID_DIR)
- stored on a remote server.

The source code of the grid access tool is part of the git repository git@git.mpimet.mpg.de:icon_grid_table.git. A binary of the grid access tool is located in ~routfor/routfox/patch/.
The file name of the XML table must be set as an environment variable ICON_XML_GRID_TABLE.
On DWD's HPC cluster, for example, the following settings should be made in your .profile / .bashrc / etc.:

export PATH="~routfor/routfox/patch/:"$PATH

export ICON_GRID_DIR=~routfor/routfox/icon/grids/public/edzw

export ICON_XML_GRID_TABLE=~routfor/routfox/icon/xml/dwd_grids.xml

Then the grid file can be located with the grid access tool using the following syntax:

Usage: icon_grid_get number_of_grid_used centre subcentre

Example.

    
      icon_grid_get 1 78 255 
      
      icon_grid_get v.1.0.1
      
      numberOfGridUsed : 1
      centre           : 78
      subcentre        : 255
      type             : horizontal
      
      Description      : Reduced radiation grid (global, R02B05). 80 km resolution
      URI              : grids/public/edzw/icon_grid_0001_R02B05_R.nc
      ExtPar           : grids/public/edzw/icon_extpar_0002_R02B06_G.nc
      
      Contained in grid set(s):
      - "Global R02B06 grid hierarchy without nests."
      numberOfGridUsed: 1, centre: 78, subcentre: 255, type: hrz_radiation
      numberOfGridUsed: 2, centre: 78, subcentre: 255, type: hrz_global
      
      search for "icon_grid_0001_R02B05_R.nc"...
      File found in
      /e/rhome/routfor/routfox/icon/grids/public/edzw/icon_grid_0001_R02B05_R.nc

How does the XML grid description look like?

The table is stored in XML format, which is more or less human-readable. It consists of paragraphs of the following form:

    
      <grid oper                = "yes"
          number_of_grid_used = "2"
          centre              = "78"
          subcentre           = "255"
          type                = "hrz_global">
          <description>
              Global R02B06 grid.
              40 km resolution
          </description>
          <uri>grids/public/edzw/icon_grid_0002_R02B06_G.nc</uri>
          <extpar>
              <uri>grids/public/edzw/icon_extpar_0002_R02B06_G.nc</uri>
              <description>Globcover-based data set.</description>
          </extpar>
      </grid>

The optional oper attribute allows to mark a specific grid as operational.
The <description> tag allows to describe the grid properties in a few words.

The XML file can also be viewed in a web browser

firefox --no-remote ${ICON_XML_GRID_TABLE}

where the table layout is then defined by the XSL definitions in xml/dwd_grids.xsl.

The XML file will later be available in tabular form on the public grid web site.

Finally, the XML file contains information on associated grids (e.g., refinement hierarchies):

    
      <gridset>
          <description>
              Global R02B04 grid hierarchy without nests.
          </description>
          <grid number_of_grid_used = "9"  
               centre              = "78"
               subcentre           = "255"
               type                = "hrz_radiation" />
          <grid number_of_grid_used = "10"  
               centre              = "78"
               subcentre           = "255"
               type                = "hrz_global" />
      </gridset>