Stratospheric Ozone Chemistry and Polar Stratospheric Clouds

- 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 ${\frac {\mathrm {d} c_{i}}{\mathrm {d} t}}=P_{i}-{\frac {c_{i}}{\tau _{i}}}$ 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 included. 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

${\ce {ClNO3 + HCl -> Cl2 + HNO3}}$

is effektively producing high ${\ce {HNO3}}$ concentrations in the stratosphere resulting in a formation of ${\ce {HNO3*H20}}$ phases, identifying as polar stratospheric clouds. The educts are existing due to the regular ${\ce {ClOx}}$ family reactions (see e.g. Dameris et al., 2007). Later ion the year, when more light reaches Antarctica, the ${\ce {Cl2}}$ product can then be photolysed and finally, due to the ${\ce {ClOx}}$ cycle, Ozone can be depleted:

${\ce {Cl2 + hv -> 2Cl}}$

${\ce {Cl + O3 -> ClO + O2}}$

That's also why the ozone hole has formed: The more chlorofluorocarbons are emitted, the more ${\ce {ClNO3}}$ as well as ${\ce {HCl}}$ 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.