wiki:ProcessingOutput

Processing DYNAMICO output

DYNAMICO outputs data on the native icasohedral grid in NetCDF-CF format, one file per field. Each file contains the data and metadata describing the grid. Most fields are associated to hexagons, but some are associated to triangles. Native files can be visualized with the VTKMapper tool developed by Patrick Brockmann. Recently ParaView has become able to visualize NetCDF-CF files too. For quantitative post-processing it is probably best to interpolate to Cartesian curvilinear coordinates such as lat-lon.

Visualization with VtkMapper

VTKmapper is available under the CeCILL open source license. It is written in Python and requires python-netcdf4 as well as the NetCDF and VTK libraries. These prerequisites should be easily available on Linux systems. On a recent MacOS they can be installed using macports (Python 2.7 assumed below) :

sudo port selfupdate
sudo port select --set python python27
sudo port install py-netcdf4
sudo port install vtk5 +python27

VTKMapper allows efficient, basic visualization on the native mesh :

mapper.py -n 100 -p orthographic ps.nc ps

Visualization with Paraview

DYNAMICO, with or without XIOS, now produces files that can be directly read and visualized by Paraview.

Grouping fields together for nco and cdo post-processing

cdo can interpolate from unstructured meshes to lat-lon grids. However it also needs in a single file data and metadata that are currently split in separate files, unless XIOS output is used. The following commands will merge the necessary data in a single file that can be processed by cdo.

ncks -O time_counter.nc merged.nc
ncks -A apbp.nc merged.nc
ncks -A ps.nc merged.nc

At this point merged.nc contains the surface pressure data (ps.nc) and the metadata expected by CDO. Additional fields can be merged into the same file using 'ncks -A' provided they are associated to hexagons. This includes potential temperature (theta.nc), surface geopotential (phis.nc), geopotential (phi.nc).

The above manipulations are not needed on files written through XIOS. These files can directly be used with cdo.

Interpolation to lat-lon with nco and cdo

CDO needs a text file describing the target grid :

cat > mygrid << EOF
gridtype = lonlat
xsize    = 360
ysize    = 180
xfirst   = −179.5
xinc     = 1
yfirst   = -89.5
yinc     = 1
EOF

In the above example the text file mygrid describing regular mesh with 1-degree resolution is created. Finally cdo can be invoked to interpolate all fields to a lat-lon grid :

cdo remapdis,mygrid merged.nc latlon.nc

latlon.nc can now be visualized using ncview or read/processed by standard tools.

This procedure is an interim solution which should be replaced by built-in output to lat-lon grids in the near future.

Last modified 3 years ago Last modified on 09/30/14 15:31:36