New perspectives in mesospheric wave dynamics and oxygen photochemistry
Licentiate thesis, 2020
Atmospheric gravity waves are internal disturbances in the medium that propagate horizontally and vertically. Based on linear wave theory, this thesis attempts to enhance our understanding of the relationships between the wave characteristics, the mean flow and the sources. We try to emphasise the frequency change due to the Doppler effect in several reference frames. This thesis proposes a consistent framework for deriving those wave parameters that cannot be obtained from a single type of instrument due to their particular observational geometry. Finally, a plausible interpretation of a readily available ground-based lidar observation is given as an example.
Oxygen photochemistry is another important aspect in this thesis. The underlying chemical reactions are affected by disturbances in the local temperature and density, which in turn changes the distribution of the excited oxygen species. In this work, a photochemical model has been implemented, which describes most of the important processes such as O3 photolysis that are related to the production and loss of O(1D), O2(b1Σg+ ) and O2(a1∆g).
The observation of airglow emissions provides an opportunity to explore the chemical composition and wave dynamics in the upper mesosphere. The Odin satellite has been routinely measuring O2(a1∆g) airglow emissions since 2001. In this thesis, data collected by OSIRIS are explored. Inversions are carried out in order to retrieve the volume emission rate of O2(a1∆g) as well as the mesospheric ozone density. The resulting ozone profiles are shown to be consistent with other independent ozone datasets collected by instruments aboard the same spacecraft as well as ACE-FTS and MIPAS, despite intrinsically different measurement principles. The overall good agreement between them illustrates the good performance of the retrieval technique. Furthermore, these investigations serve well as a preparatory activity for the upcoming satellite mission MATS, set for launch later this year.
Satellite limb observation
Chalmers, Space, Earth and Environment, Microwave and Optical Remote Sensing
Anqi Li, Chris Roth, Kristell Pérot, Ole Martin Christensen, Adam Bourassa, Doug Degenstein and Donal Murtagh. Retrieval of daytime mesospheric ozone using OSIRIS observation of O2(a1∆g) emission
Anqi Li, Ole Martin Christensen, Andreas Dörnbrack, Patrick Espy, Alexander Kozlovsky, Mark Lester, Robert Reichert and Donal Murtagh. Perspectives on interpretation of a gravity wave event recorded by ground-based lidar
Mesospheric Transport Processes
Swedish National Space Board (158/17), 2018-01-01 -- 2021-12-31.
MATS 2018-2021 at Chalmers
Swedish National Space Board (299/17), 2018-01-01 -- 2021-12-31.
Meteorology and Atmospheric Sciences
Opponent: Christian von Savigny, University of Greifswald, Germany