Postprocessing

Output Checks with SAMOA

SAMOA performs a sanity check on all model outputs that can be read by CDO. It checks if a variable lies in-between a predefined range and if the minimum and maximum value of each variable are the same. For this purpose CDO version 1.6.2rc3 is required currently (see https://code.zmaw.de/projects/cdo).

For more information about the usage please refer to the README-file within the SAMOA package. You can get a copy of the SAMOA script by writing an e-mail to the contact person of the ART code (see http://icon-art.imk-tro.kit.edu). SAMOA is licensed under the GNU GENERAL PUBLIC LICENSE Version 3.

As SAMOA is primarily developed for the usage with COSMO-ART and COSMO-CLM, you have to do a minor change before using it. The latest version of SAMOA has a list for the usage of SAMOA with ICON-ART output included but not loaded automatically. This list is called samoa_list_icon-art. You have to replace the default (COSMO) list that is used by SAMOA by editing samoa.sh:

Search for the following lines:

# Path to the list with variables (is overwritten when -l specified)
# Assumed to be on the same path as script

path_list=$SCRIPTPATH/list 

Change the name of the list to:

path_list=$SCRIPTPATH/samoa_list_icon-art 

Now you may use SAMOA with the ICON-ART output file out.nc with the following command:

./samoa.sh out.nc

For all options see:

./samoa.sh --help

Visualisation

The horizontal grid structure of the output is essential for the visualization. In general, there are two possibilities. The output may exist on the ICON grid and it may exist on an interpolated longitude/latitude grid. This can be chosen by adaptions of the output namelist (see ). Although it comes along with a loss in information, it is recommended to use interpolated output. By this, the visualization is much easier to handle.

In the following sections, three tools are introduced which can be used to visualize ICON output. Note, that only NETCDF is supported by ICON-ART so far. With the tool Ncview (see ) it is very easy to have a quick look into the interpolated model output. NCL (see ) is a very comprehensive tool for all kind of data formats and visualization. With ParaView (see ), a nice-looking three-dimensional visualization can be created.

Ncview

"Ncview is a visual browser for netCDF format files. Typically you would use ncview to get a quick and easy, push-button look at your netCDF files. You can view simple movies of the data, view along various dimensions, take a look at the actual data values, change color maps, invert the data, etc." (http://meteora.ucsd.edu/~pierce/ncview_home_page.html)

Please note that Ncview does only work for latitude-longitude grid data and cannot be used for RXXBXX-style ICON grids without remapping.

NCL

"NCL is an interpreted language designed specifically for scientific data analysis and visualization. Portable, robust and free, NCL is available as binaries or open source." (https://www.ncl.ucar.edu/)

ParaView

"ParaView is an open-source, multi-platform data analysis and visualization application. ParaView users can quickly build visualizations to analyze their data using qualitative and quantitative techniques. The data exploration can be done interactively in 3D or programmatically using ParaView’s batch processing capabilities.

ParaView was developed to analyze extremely large datasets using distributed memory computing resources. It can be run on supercomputers to analyze datasets of exascale size as well as on laptops for smaller data." (http://www.paraview.org/)

Python

On the official Website Python describes itself as

Python is powerful... and fast;
plays well with others;
runs everywhere;
is friendly & easy to learn;
is Open.

Using Python is a simple but effective way to display ICON-ART model output data. There is a large number of Packages available to help with Visualisation, the most useful Packages for visualising ICON-ART data are given in Table 1.4

Helpful Python Packages and their primary usage for Visualisation

numpy	predefined Mathematical functions
matplotlib	Plotting framework
xarray	reading in and processing netcdf datasets
...