Turbulence Diagnostics

To enable a more through evaluation of turbulent processes in ICON, the option exists to calculate and write additional turbulence parameters via the namelist parameter ldiagnose_gstke in the io_nml. When this option is enabled, two additional diagnostic 3D parameters are defined and available for output. In addition to the (subgrid-scale, parameterised) turbulent kinetic energy (SGS TKE, tke), which is a prognostic variable for inwp_turb=1(the Raschendorfer Turbdiff scheme), the eddy dissipation rate (edr) and turbulent length scale (tur_len_scale) can be added to the output namelist. This writes the instantaneous value of these parameters.

The diagnostic additionally calculates a grid-scale contribution to the TKE from the temporal fluctuation of the resolved winds (gs_tke) over a pre-specified time period gstke_interval, also set in the io_nml. A temporal average of the SGS TKE and the EDR over the same specified period is also calculated and available as output variables with the names sgs_tke and avg_edr.

The sum of gs_tke and sgs_tke is then a more accurate approximation of the actual TKE of the atmosphere. As grid resolution increases, it becomes more relevant to include the contribution from the grid-scale, resolved TKE.