Stratospheric Ozone Chemistry and Polar Stratospheric Clouds

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- under construction! -

In this example a simulation with only stratospheric (simplified) ozone chemistry is performed, also polar stratospheric clouds are taken into account. The tutorial teaches you...

  • the implementation of stratospheric specific chemistry (here on thee example of ozone)
  • applying linearized ozone chemistry (LINOZ) in a simulation
  • the implementation of polar stratospheric clouds (PSCs)

No emission data will be included in this simulation.

Configuration case

Stratospheric ozone with linearized ozone chemistry (LINOZ)

On the one hand the depicted case is dealing with simulating stratospheric ozone which is calculated with a linearized ozone chemistry (LINOZ). Here a linearized version of the differential equation for production or depletion like is used. After calculating the Taylor expansion of first order the computed ozone concentrations are then anomalies from temperature and ozone column climatologies. This LINOZ chemistry is applied in heights of 10km and higher. Below that height the lifetime of ozone is set to constant 28 days so a constant climatology is applied. Without including LINOZ at this point, a complete ozone chemistry must be included in the simulation what would result in higher computational effort.

Polar Stratospheric Clouds (PSCs)

Further, the simulation of polar stratospheric clouds (PSC), are also considered. Polar stratospheric clouds are forming under very cold conditions in the antarctic region during the south hemispheric winter. These cold conditions are reached due to the underlying orographic conditions in Antarctica and a resulting very strong and stable polar vortex. In May or June the temperature is normally low enough to form polar stratospheric clouds. Then the reaction

is effektively producing high concentrations in the stratosphere resulting in a formation of phases, identifying as polar stratospheric clouds. The educts are existing due to the regular family reactions (see e.g. Dameris et al., 2007). Later ion the year, when more light reaches Antarctica, the product can then be photolysed and finally, due to the cycle, Ozone can be depleted:

That's also why the ozone hole has formed: The more chlorofluorocarbons are emitted, the more as well as are produced and the more ozone can be depleted. In this simulation, PSCs are considered to calculate the stratospheric ozone concentration but not to simulate the clouds itself.

Setting up the Runscript

Let's start with the runscript that has to be prepared. Please note that the in the following explained parts have to be printed in one runscript-file with the naming designation "xyz.run". Here it is named exp.testsuite.strat_ozone_linoz_psc.run but of course you can call it differently as well. The runscript can be stored under the following path in your icon directory: /icon-kit/run

If you've already walked through the example of the Simplified Chemistry, you can use nearly the same runscript. Note that you have to change the paths from Part 1, the timing settings from Part 2, the output variables from Part 3, the emission settings as well as the path of the chemtracer-xml-file in the ART-settings from Part 4 and finally the timing in the job settings from Part 5. Details can be found below.

Inside of that, first check in part 1 that all your paths to your directories are correct, probably they have to be adjusted. Note that "hp8526" is a name of a specific account here, make sure to double check especially these lines. Abbreviations used here are the following:

  • CENTER: Your organization
  • EXPNAME: name of your ICON-Simulation
  • OUTDIR: Directory where the simulation output will be stored
  • ARTFOLDER: Directory where the ICON-ART code is stored
  • INDIR: Directory where the necessary Input data are stored
  • EXP:
  • lart: For ICON-ART Simulation that has to be switched to .True..

Part 1: Runscript Directory Settings (Example configuration)

Additionally in the next lines of code you set the timing. In this simulation we simulate one week (01 October 2012 until 07 October 2012). To really catch all day times and so the time dependent solar radiation, the output interval is set to 10 hours to calculate to every time of the day. Because of the Photolysis dependency of this is particularly important.

Part 2: Runscript Timing Settings (Example configuration)

Further, all the namelist parameters (from the regular ICON model without ART-extension) have to be set. For a regular ICON-ART-Simulation the following settings are recommended - if not stated differently. For a detailed description, check out the ICON Documentation (Drill et. al. (2019)).

Since we make use of LINOZ, in the radiation namelist section &radiation_nml the namelist parameter irad_o3 has to be set to 10:

Part 3: Runscript ICON-Parameter and -Namelist Settings (Example configuration)

Please note in the last namelist section "output_nml" that you can set all output variables that you need to postprocess your data later. All assigned variables here will be written in the output netCDF-files as well. To learn more about post processing your data, check out a later chapter of this article or the Postprocessing article.

Now, we're getting to the ICON-ART settings. To enable chemistry in an ICON-ART Simulation inn general, the switch lart_chem has to be set to .TRUE.. With lart_diag_out output of the diagnostic fields can be enabled. Due to setting lart_chem=.TRUE. either lart_chemtracer or lart_mecca has to be set to .TRUE.. Because we want to perform a simulation with simplified chemistry, we have to switch on lart_chemtracer. If this namelist parameter is set to .TRUE., also cart_chemtracer_xml has to be fulfilled. Here you enter the path of your xml-file which describes the tracers occurring and their properties in the simulation, which is only in this case. How to create this xml-file is explained in the next chapter. Since PSCs shall be considered, the lart_psc switch has to be set to .TRUE.. Please also note the extra information that have to be given for in the xml-file that PSCs are considered correctly (see next chapter). An example configuration for this part is shown in the following:

Part 4: Runscript ICON-ART Settings (Example configuration)

Depending on the used HPC-System, some parameter concerning the running job like maximum running time and used nodes can be set. For this case study the following settings can be copied. Note that this is valid for the HoreKa HPC system and that it can differ to other systems.

Part 5: Runscript job Settings (Example configuration)

To conclude and to double check, in the following box the complete runscript is shown once again.

Complete example configuration of the runscript