Since the discovery in 1985 of the ozone hole over the Antarctic, extensive measurement campaigns have led to a fairly good understanding of its origin. Ozone depletion is caused by catalytic chemical reactions by halogen atoms like chlorine, released from man-made chlorofluorocarbons (CFC). The large increase in concentration of active chlorine (ClO and Cl) is caused by heterogeneous chemical reactions on polar stratospheric cloud particles. Similar, but smaller, disturbances can also be seen over the Arctic and even at lower latitudes.
On a global scale, the depletion process is rather complex, involving atmospheric transport phenomena, variations of ozone chemistry at different altitudes, and large natural variations.
In order to build better models, both altitude determination and geographical mapping of key components were provided by Odin.
So this research will address scientific problem areas in the stratosphere and mesosphere by making measurements of various trace species. The scientific goals can be summarized as follows:
- Stratospheric ozone science: to elucidate the geographical extent of and mechanisms responsible for ozone depletion in the "ozone hole" region and to study dilution effects and possible heterogeneous chemistry even outside of polar regions due to sulphate aerosols.
- Mesospheric ozone science: to establish the relative role of odd hydrogen chemistry and the effects of ordered and turbulent transport and corpuscular radiation.
- Summer mesospheric science: to establish the variability of mesospheric water vapour including an assessment of the required fluxes for aerosol formation in the polar mesosphere.
- Coupling of atmospheric regions: to study some of the mechanisms that provide coupling between the upper and lower atmosphere, e.g. downward transport of aurorally enhanced NO with its effects on ozone photo chemistry and the vertical exchange of minor species such as odd oxygen, CO and H2O.