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

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

Visualization with Paraview

Paraview requires some data and metadata that are not currently provided in the NetCDF output. Yann has done the required modifications and will commit them soon.

Interpolation to lat-lon with nco and cdo

​cdo can interpolate from unstructured meshes to lat-lon grids. However it also needs in a single file data and metadata that are current split in separate files. 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 hexagons. This includes potential temperature (theta.nc), surface geopotential (phis.nc), geopotential (phi.nc).

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.