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5. Summary

Five years of observational spectroscopic data of NO₂ and O₃ columns measured at 3 austral stations separated by 10º in latitude have been used to analyse meridional differences in seasonal features. The stations are representative of mid latitudes, the edge, and the core of the Antarctic polar vortex. NO₂ seasonal wave in the higher latitude stations are strongly modulated by the denitrification processes within the vortex as can be seen by the strong asymmetry between autumn and spring in the amount of NO₂ as a function of the hours of light. The wave is also sensitive to the lower stratospheric temperature and the PV (relative position of the vortex respect the stations). SLIMCAT model reproduces qualitatively well the seasonal evolution but in general underestimates the column in Ushuaia and during the equinoxes in the other two stations. On the other hand, diurnal variations in winter and spring are greater in the model. Ozone data have been intercompared as well. At Marambio and Belgrano SLIMCAT display an almost linear decay from the summer maximum up to the beginning of the depletion which is not be confirmed because of lack of direct integrated measurements. Ozonesondes data, however, suggest that the model provides lower ozone at high latitudes in winter. This underestimation is attributed to the SLIMCAT grid, too coarse for the polar areas, as the model is averaging data from lower illuminated latitudes where depletion starts in July.