The origin of ozone

V. Grewe (1)

1 IPA - DLR Institut für Physik der Atmosphäre = DLR Institute of Atmospheric Physics

Highest ozone production rates can be found at around 30 km in the tropical stratosphere, leading to ozone mixing ratios of about 10 ppmv. Those stratospheric air masses are then transported to extra-tropical latitudes via the Brewer-Dobson Circulation. This is thought to be the main mechanism, how mid- and high latitude ozone is generated. By applying the climate-chemistry model E39/C, this view is investigated in more detail. The origin of ozone in the troposphere and stratosphere is analyzed, by incorporating a diagnostic (''marked ozone origin tracers'') into the model, which allows to identify the origin of ozone. In most regions the local simulated ozone concentration is dominated by local ozone production, i.e. less than 50% of the ozone at higher stratospheric latitudes is produced in the tropics, which conflicts with the idea that the tropics are the global source for stratospheric ozone. Although episodic stratospheric intrusions occur basically everywhere, the main ozone stratosphere-to-troposphere exchange is connected to exchange processes at the sub-tropical jet-stream. The tropospheric influx of ozone amounts to 420 Tg per year, and originates on the Northern Hemisphere from the extra-tropical stratosphere, whereas on the Southern Hemisphere a re-circulation of tropical tropospheric ozone contributes most to the influx of ozone into the troposphere. In the model, the upper tropopause of both hemispherers is clearly dominated by tropical tropospheric ozone (40%?50%) except for Northern Summer, where the tropospheric contribution (from the tropics as well as from the Northern Hemisphere) does not exceed 20%.

Domaines: Océan, Atmosphère

V. Grewe. The origin of ozone. Atmospheric Chemistry and Physics Discussions, 2005, 5 (5), pp.9641-9668. ⟨hal-00301834⟩