Spatio-temporal observations of tertiary ozone maximum

In this work, we present spatio-temporal distributions of tertiary ozone maximum based on GOMOS (Global Ozone Monitoring by Occultation of Stars) ozone measurements in 2002-2006. The tertiary ozone maximum is typically observed in high-latitude winter mesosphere at altitude ~72 km. Although the explanation for this phenomenon has been found recently - low concentrations of odd-hydrogen cause the subsequent decrease in odd-oxygen losses - models have had significant deviations from existing observations until recently. Good coverage of polar night regions by GOMOS data has allowed for the first time obtaining spatial and temporal observational distributions of night-time ozone mixing ratio in the mesosphere.

The distributions obtained from GOMOS data have specific features, which are variable from year to year. In particular, due to long lifetime of ozone in polar night conditions, the downward transport of the polar air by the meridional circulation is clearly observed in the tertiary ozone time series. Although the maximum of mixing ratio is achieved close to the polar night terminator (as predicted by the theory), the tertiary ozone maximum can be observed also at very high latitudes, not only in the beginning and at the end, but also in the middle of winter. We have compared the observational spatio-temporal distributions of tertiary ozone maximum with that obtained using WACCM (Whole-Atmosphere Community Climate Model) and found that the specific features are well reproduced by the model.

Since ozone in the mesosphere is very sensitive to HOx concentrations, energetic particle precipitation can significantly modify the shape of ozone profiles. In particular, GOMOS observations have shown that the tertiary ozone maximum was temporarily destroyed during the January 2005 solar proton events as a result of the HOx enhancement from the increased ionization.