Gravity Wave Mixing Effects on the OH*-layer

Publication date: Available online 11 October 2019Source: Advances in Space ResearchAuthor(s): E. Becker, M. Grygalashvyly, G.R. SonnemannAbstractBased on an advanced numerical model for excited hydroxyl (OH*) we simulate the effects of gravity waves (GWs) on the OH*-layer in the upper mesosphere. The OH* model takes into account 1) production by the reaction of atomic hydrogen (H) with ozone (O3), 2) deactivation by atomic oxygen (O), molecular oxygen (O2), and molecular nitrogen (N2), 3) spontaneous emission, and 4) loss due to chemical reaction with O. This OH* model is part of a chemistry-transport model (CTM) which is driven by the high-resolution dynamics from the KMCM (Kühlungsborn Mechanistic general Circulation Model) which simulates mid-frequency GWs and their effects on the mean flow in the MLT explicitly. We find that the maximum number density and the height of the OH*-layer peak are strongly determined by the distribution of atomic oxygen and by the temperature. As a results, there are two ways how GWs influence the OH*-layer: 1) through the instantaneous modulation by O and T on short time scales (a few hours), and 2) through vertical mixing of O (days to weeks). The instantaneous variations of the OH*-layer peak altitude due to GWs amount to 5-10 km. Such variations would introduce significant biases in the GW parameters derived from airglow when assuming a constant pressure level of the emission height. Performing a sensitivity experiment we find that on ave...

Source: Advances in Space Research - October 12, 2019 Category: Science Source Type: research