Experiment 3 - Size of initial perturbation#

The initial temperature field in the suite is perturbed by a small random noise to induce convective motions, which subsequently grow larger due to convective instability. To test the sensitivity of the experiment outcome to this perturbation, we suggest changing the amplitude of this perturbation and comparing the results to the control experiment.

The parameters that control the initial perturbation are: perturb_init (to switch it on), perturb_magnitude (base-10 logarithm of the perturbation magnitude), and perturb_seed - random seed. In the GUI, they are stored in the lfric_atm -> Run Task Settings -> Job -> Initial Conditions.

In the configuration file the namelist is

Listing 11 app/lfric_atm/rose-app.conf#
[namelist:idealised]
f_lon_deg=0.0
perturb_init=.true.
perturb_magnitude=1
perturb_seed=180906
test='specified_profiles'

Note

There are other perturbation options in the “Temperature” tab, e.g. perturb and pert_width_scaling, but we are not using them in this practical.

Step 1: Change perturbation magnitude#

Running graphical applications over SSH

If you are connected to a remote system over SSH, graphical applications need X11 forwarding to display on your computer. Start an X server on your computer first (for example, XQuartz on macOS), then connect from a terminal using generic host details supplied by your service:

$ ssh -AY <remote-host>

Repeat the options for every additional SSH hop. The -Y option enables trusted X11 forwarding. The -A option forwards your SSH authentication agent and should only be used with systems you trust. A terminal integrated into an editor such as VS Code works in the same way as any other terminal.

On the system where you will start the graphical application, run echo "$DISPLAY". It should return a value. If it is blank, disconnect and reconnect with X11 forwarding enabled at every hop before continuing.

rose edit &

See also

For help choosing the correct Monsoon3 service and finding the official setup guidance, see Using Monsoon3.

rose edit &

Note

You must be using the Cylc host to access rose-edit.

What does the rose-edit & command do?

  • This command opens the suite in the Rose graphical user interface, allowing you to view and modify its configuration.

  • The & at the end runs the GUI in the background, so your terminal remains available for other commands.

  1. Open Rose GUI or app/lfric_atm/rose-app.conf in a text editor of your choice.

  2. Search for the perturb_init key.

  3. Change the value from 0 to 1 (or 2).

Step 2: Run the model#

Now that you have changed the configuration, run the model using what you have learnt in the previous exercises. Check the output using Python or another tool of your choice

Step 3. Compare with the control experiment#

Using a Python script or Jupyter Notebook, make plots for both experiments and compare them to each other to see the effect of the perturbation magnitude.