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- ItemDaytime ozone loss term in the mesopause region(Katlenburg, Lindau : Copernicus, 2017-5-23) Kulikov, Mikhail Y.; Belikovich, Mikhail V.; Grygalashvyly, Mykhaylo; Sonnemann, Gerd R.; Ermakova, Tatiana S.; Nechaev, Anton A.; Feigin, Alexander M.For the retrieval of atomic oxygen via ozone observations in the extended mesopause region under sunlight conditions, two assumptions are used: first, the photochemical equilibrium of ozone and, second, that the ozone losses are dominated by ozone's dissociation from solar UV radiation, silently ignoring the O3 destruction by atomic hydrogen. We verify both by 3-D modeling. We found that ozone approaches photochemical equilibrium at 75–100 km for daytime conditions. Hence, the first assumption is valid. However, the reaction of ozone with atomic hydrogen was found to be an important loss process and should not be omitted in retrieving atomic oxygen.
- ItemSemi-annual variation of excited hydroxyl emission at mid-latitudes(Katlenburg, Lindau : Copernicus, 2021) Grygalashvyly, Mykhaylo; Pogoreltsev, Alexander I.; Andreyev, Alexey B.; Smyshlyaev, Sergei P.; Sonnemann, Gerd R.Ground-based observations show a phase shift in semi-annual variation of excited hydroxyl (OH∗) emissions at mid-latitudes (43∘ N) compared to those at low latitudes. This differs from the annual cycle at high latitudes. We examine this behaviour by utilising an OH∗ airglow model which was incorporated into a 3D chemistry–transport model (CTM). Through this modelling, we study the morphology of the excited hydroxyl emission layer at mid-latitudes (30–50∘ N), and we assess the impact of the main drivers of its semi-annual variation: temperature, atomic oxygen, and air density. We found that this shift in the semi-annual cycle is determined mainly by the superposition of annual variations of temperature and atomic oxygen concentration. Hence, the winter peak for emission is determined exclusively by atomic oxygen concentration, whereas the summer peak is the superposition of all impacts, with temperature taking a leading role.