Hydroxyl airglow observations for investigating atmospheric dynamics: results and challenges

Abstract

Abstract. Measurements of hydroxyl (OH*) airglow intensity are a straightforward and cost-efficient method which allows the derivation of information about the climate and dynamics of the upper mesosphere/lower thermosphere (UMLT) on different spatiotemporal scales during darkness. Today, instrument components can be bought “off-the-shelf” and developments in detector technology allows operation without cooling, or at least without liquid nitrogen cooling, which is difficult to automate. This makes instruments compact and suitable for automated operation. Here, we briefly summarize why an OH* airglow layer exists, how atmospheric dynamics influence it and how temperature can be derived from OH* airglow measurements. Then, we provide an overview of the scientific results regarding atmospheric dynamics (mainly gravity waves (GWs) but also planetary waves (PWs) and infrasound) achieved with OH* airglow measurements. We focus on long-term ground-based OH* airglow measurements or airglow measurements using a network of ground-based instruments. The paper includes further results from global or near-global satellite-based OH* airglow measurements, which are of special importance for characterizing the OH* airglow layer. Additionally, the results from the very few available airborne case studies using OH* airglow instruments are summarized. Scientific and technical challenges for the next few years are described.

Occurrence of Mesospheric Frontal Structures Over the High Latitude Station, Tromsø, Norway

“…The local time distribution plotted is similar to the previous reports on GWs by J. Li et al. (2020) from the Arctic region (Wüst et al., 2023). The average number of trailing waves behind the bore front was determined to be two (Figure 5c).…”

Multi-instrumental observation of mesoscale tropospheric systems in July 2021 with a potential impact on ionospheric variability in midlatitudes

“…In particular, OH nightglow with a mean emission altitude of approximately 86 km is well-suited to investigate the dynamics in the upper mesosphere and lower thermosphere region (see Wüst et al, 2023 and references given therein). The OH nightglow layer has its strongest emission in the short-wave infrared range at approximately 1.5-1.6 µm [rotational-vibrational transitions OH(3-1) and OH(4-2)].…”

A novel infrared imager for studies of hydroxyl and oxygen nightglow emissions in the mesopause above northern Scandinavia

“…In particular, the temperature of emission layers in the middle and upper atmosphere can be determined by analyzing spectral bands and lines of airglow emissions. By analyzing spatial-temporal variations in the emission intensities and/or temperature, one can investigate the short-and long-term dynamical state of the middle and upper atmosphere, which in turn is a hot topic of current atmospheric research (e.g., Fritts and Alexander, 2003;Plougonven and Zhang, 2014;Reid et al, 2014;Wüst et al, 2023;Gavrilov et al, 2024). The key role in the atmospheric dynamical state belongs to waves, a fundamental property of the atmosphere as they transport energy and momentum across great distances (Gossard and Hook, 1975).…”