The origin of ozone

[摘要] Highest atmospheric ozone production rates can be found at around 30 kmin the tropical stratosphere, leading to ozone mixing ratios of about 10 ppmv.Those stratospheric air masses are then transported to extra-tropicallatitudes via the Brewer-Dobson circulation. This is considered the mainmechanism to generate mid- and high latitude ozone.By applying the climate-chemistry models E39/C and MAECHAM4/CHEM,this view is investigated in more detail.The origin of ozone in the troposphere and stratosphere is analysed, byincorporating a diagnostics ("marked ozone origin tracers") into the models,which allows to identify the origin of ozone.In most regions the simulated local ozone concentration is dominated by local ozoneproduction, i.e. less than 50% of the ozone at higher latitudesof the stratosphere isproduced in the tropics, which conflicts with the idea that the tropicsare the global source for stratospheric ozone.Although episodic stratospheric intrusions occur basically everywhere,the main ozone stratosphere-to-troposphere exchange is connectedto exchange processes at the sub-tropical jet-stream.The simulated tropospheric influx of ozone amounts to 420 Tg per year, and originatesin the Northern Hemisphere from the extra-tropical stratosphere, whereasin the Southern Hemisphere a re-circulation of tropical tropospheric ozonecontributes most to the influx of ozone into the troposphere.In the model E39/C, the upper troposphere of both hemispheres is clearly dominated by tropicaltropospheric ozone (40%–50%) except for northern summer hemisphere, where the troposphericcontribution (from the tropics as well as from the Northern Hemisphere) does notexceed 20%.

[学科分类] 大气科学