Overview

The single column model (SCM) represents a single gridpoint in IFS and allows all the physical processes to be run in a single vertical column.

 IFS cycle 43r3 was the operational model at ECMWF from July 2017 to June 2018.

SCM 43r3 will not produce the same results as the previous release SCM 40r1. This is due to significant changes to the representation of the physical processes and a new radiation code.

Support

Please report any issues or problems with this release to either the OpenIFS User Forums or the openifs-support@ecmwf.int email.

Model documentation

For a full description of the physical processes included in the single column model, please see the IFS CY43r3 Physical Processes manual (PDF).





Summary of changes

For more details of the changes introduced at IFS 43r3 and previous operational models (since 40r1) please see: Changes in ECMWF IFS model.

Brief summary:

  • new radiation scheme ecRAD (see below), more efficient with reduced noise and more accurate longwave radiation transfer calculation.
  • revised interpolation of moist variables in the upper-troposphere / lower stratosphere (UTLS).
  • cloud scheme change of rain evaporation, auto-conversion/accretion, riming, precipitation fraction.
  • increased super-cooled liquid water at colder temperatures from the convection scheme.
  • improved representation of supercooled 'freezing rain'.
  • modified convective detrainment.
  • changed parcel perturbation for deep convection to be proportional to surface fluxes.
  • increased cloud erosion rate when convection is active to reduce cloud cover slightly particularly over ocean.
  • changes to boundary layer cloud for marine stratocumulus and at high latitudes.
  • introduced resolution dependence in parametrization of non-orographic gravity wave drag.
  • new output diagnostics fields.

New radiation code ecRAD



Technical aspects

Requirements

netCDF. The SCM requires the netCDF library to be available in order to read and write files.

Namelists

There are two namelist files in the scm-40r1.ref-oifs/test-run directory:
           namelist.trref_winds_rel  and  namelist.trref_winds_rel.simpl

The former one defines non-linear physics, the latter one the simplified physics (you may be surprised how close the results from the two packages are). We expect most users to use the full non-linear physics option.

It is important to set NRADINT=0 in the namelist &NAERAD. If not the model will abort as the default configuration is for 3D runs where the IFS uses a reduced grid to compute the radiation.

Semi-Lagrangian

By default the semi-Lagrangian scheme is activated (LSLAG=.T.) with the physics being averaged along a trajectory (LSLPHY=.T.). This follows the defaults in the IFS.

If you like to use Eulerian advection set LSLAG=.F., reduce the model timestep (don't forget to change number of time steps accordingly) and disable the semi-Lagrangian physics by setting LSLPHY=.F.