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Previously you have carried out an OpenIFS control experiment of Tropical Cyclone Karl.  In this tutorial you will learn:

  • How to include output physical tendencies and fluxes in OpenIFS
  • How to scale temperature tendencies in a rectangular domain

Latent Heat Fluxes

The scientific presentations during the morning programme of the workshop have given examples for how cyclogenesis in general and the life cycle of tropical storms in particular are sensitive to temperature dependencies from physical processes, such as convection.

In the perturbation experiments it is possible to modify temperature tendency contributions from the model physics (cloud, convection and radiation) in a specific region.

The temperature tendencies are produced through model dynamics and model physics:


\[ \frac{dT}{dt} = \frac{dT}{dt}(\mbox{dynamics}) + \frac{dT}{dt}(\mbox{physics}) \]

with 

\[ \frac{dT}{dt}(\mbox{physics}) = \frac{dT}{dt}(\mbox{convection}) + \frac{dT}{dt}(\mbox{clouds}) + \frac{dT}{dt}(\mbox{radiation}) \]

The contributions from the individual physical tendencies can be output in OpenIFS as an additional diagnostic using the PEXTRA output.

The additional PEXTRA diagnostics have already been set up in this workshop's model experiment.

For reference and to learn how to enable this diagnostic output in OpenIFS please find the documentation here.  On this page also a pdf document with grid code table for the tendencies can be found.

Regional scaling of tendencies

Our version of OpenIFS used in this workshop includes an additional source branch which permits regional modification of the physical tendencies in a rectangular box domain.

Moreover, this rectangular box domain can be defined in location and size, and it moves linearly in time with a constant longitudinal and latitudinal vector. The movement rate can be defined but stays constant during the experiment.

The intention is to capture the location of TC Karl with the box and modify physical temperature tendencies in this location.

For this to succeed the size of the box and it's movement direction and movement rate need to be defined.  Note that the picture below is only illustrative and the shown box does not reflect the default values set in the model. 

[ Picture ]

Namelist control of the perturbation box domain

The parameters of the box are defined in the namelist NAMLHBOX in fort.4.

&NAMLHBOX

  LBOXMODIFY_CLOUD=true,    ! enable cloud scheme T tendency
  LBOXMODIFY_CONV=true,     ! enable convection T tendency
  LBOXMODIFY_RAD=true,      ! enable radiation T tendency

  ZBOXTIMESTART=0.,         ! box start time in hours
  ZBOXTIMEEND=96.,          ! box end time in hours

  ZBOXLONWEST=295.7,        ! box western longitude boundary in degrees
  ZBOXLONEAST=305.7,        ! box eastern longitude boundary in degrees
  ZBOXLATSOUTH=28.8,        ! box southern latitude boundary in degrees
  ZBOXLATNORTH=38.8,        ! box northern latitude boundary in degrees

  ZBOXPRESSTOP=20000.,      ! box top level pressure in Pa (eg. 50000Pa)
  ZBOXPRESSBOT=90000.,      ! box bottom level pressure in Pa (eg. 90000Pa)

  ZBOXDLONBORDER=5.,        ! box longitude interpolation zone width in degrees
  ZBOXDLATBORDER=5.,        ! box latitude interpolation zone width in degrees
  ZBOXDPRSBORDER=5000.,     ! box pressure interpolation zone width in Pa

  ZBOXDLON=-0.667,          ! change in box longitude in degrees/hour
  ZBOXDLAT=0.333,           ! change in box latitude in degrees/hour

  ZBOXVALUE=1.0,            ! value of the multiplying factor inside the box
/

Submitting perturbation experiments

In order to carry out a perturbation experiment we will either apply changes to the experiment initial or boundary conditions and/or modify the model experiment parameters in the namelist.

Changing the parameters defining the regional box domain is one recommended option.

We will then resubmit the h7cc control experiment to the batch scheduler with these changes applied.

Note:  This will not change the experiment ID which is coded into the output grib files.

If the output folder name in OIFS_RUN is not changed then the output files from the previous control experiment will be either overwritten or the Grib output will be concatenated.

Therefore you should carry out the following tasks:

Tasks - Submit perturbation experiment
  1. Move the folder  output1  from the control experiment to a meaningful name (e.g. output_ctrl) or change the OIFS_RUN variable in the OIFS_RUN script.
  2. Apply the selected changes to the experiment (e.g. namlhbox, initial conditions, etc)
  3. Resubmit the experiment as a perturbation experiment with   qsub ./run.ccb

Summary

  • Backup the results of your control run by renaming the output folder. Do this first to ensure you do not inadvertently overwrite your control experiment results.
  • Discuss within your group which perturbation experiment you would like to carry out.
  • Consider which likely results you expect to see from your perturbation (what are the key output parameters to check?  what kind of plots would illustrate your likely findings?).
  • If you intend to use the namlhbox domain you should first convince yourself that its geographical and vertical extent, its movement rate and direction, meet the needs of your experiment (does it really follow TC Karl? which parameters do you wish to scale?  which scaling factor?).
  • Apply the selected changes to your experiment and resubmit the model experiment.
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