The response of oxygen(1S) and hydroxyl emission brightness to gravity wave perturbations

The middle atmosphere exhibits a wide range of dynamical and photochemical phenomena. It is also a region where gravity waves play a dominant role in atmospheric dynamics, such as energy and momentum transfer, temperature and wind fluctuation, and constituent structure. A complete understanding of gravity waves is therefore essential due to their effects and influences on the phenomena in the atmosphere. The Airborne Lidar and Observations of Hawaiian Airglow (ALOHA) Campaign was conducted in 1993 to explore the nature of gravity wave activities and the roles they play. Among many observations, one of the most exciting wave events, known as “wall event”, was observed on October 10, 1993, when a wave structure with a sharp front covering significant parts of the sky was observed to move with a phase velocity of 76 m/s at a period of 4–5 min; and meanwhile, MF radar measurements indicated that the average winds in the direction of the wave motion were at about 17m/s at OH heights, and less than 10m/s above. Remarkably, simultaneous observations of the Green line O(1S) and OH emission brightness showed an approximate and persistent 180° phase difference.; In this thesis, we propose the presence of a fully guided gravity wave is responsible for the observed 180° phase reversal between O( 1S) and OH emission. Since one can show that a fully horizontally guided gravity wave mode can occur [Munasinghe et al, 1998] at the height levels of O(1S) and OH peaks, with its wave parameters very close to those observed on October 10, 1993 during the ALOHA Campaign, we compute this gravity wave mode in presence of the observed background winds. We then compute the integrated airglow response of O(1S) and OH to this fully guided gravity wave mode. Our results showed a 191° phase difference between the O(1S) and OH emission brightness, which is consistent with the observed phase reversal. We also investigated the reasons for this behavior. Finally we conclude that the presence of the fully guided wave mode in the presence of the background winds can quantitatively explain the observed phase reversal in the ALOHA-93 Campaign.