Abstract
Abstract. We describe in this study the analysis of small and large horizontal-scale gravity waves from datasets composed of images from multiple mesospheric airglow emissions as well as multistatic specular meteor radar (MSMR) winds collected in early November 2018, during the SIMONe–2018 (Spread-spectrum Interferometric Multi-static meteor radar Observing Network) campaign. These ground-based measurements are supported by temperature and neutral density profiles from TIMED/SABER (Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry) satellite in orbits near Kühlungsborn, northern Germany (54.1∘ N, 11.8∘ E). The scientific goals here include the characterization of gravity waves and their interaction with the mean flow in the mesosphere and lower thermosphere and their relationship to dynamical conditions in the lower and upper atmosphere. We have obtained intrinsic parameters of small- and large-scale gravity waves and characterized their impact in the mesosphere via momentum flux (FM) and momentum flux divergence (FD) estimations. We have verified that a small percentage of the detected wave events is responsible for most of FM measured during the campaign from oscillations seen in the airglow brightness and MSMR winds taken over 45 h during four nights of clear-sky observations. From the analysis of small-scale gravity waves (λh < 725 km) seen in airglow images, we have found FM ranging from 0.04–24.74 m2 s−2 (1.62 ± 2.70 m2 s−2 on average). However, small-scale waves with FM > 3 m2 s−2 (11 % of the events) transport 50 % of the total measured FM. Likewise, wave events of FM > 10 m2 s−2 (2 % of the events) transport 20 % of the total. The examination of large-scale waves (λh > 725 km) seen simultaneously in airglow keograms and MSMR winds revealed amplitudes > 35 %, which translates into FM = 21.2–29.6 m2 s−2. In terms of gravity-wave–mean-flow interactions, these large FM waves could cause decelerations of FD = 22–41 m s−1 d−1 (small-scale waves) and FD = 38–43 m s−1 d−1 (large-scale waves) if breaking or dissipating within short distances in the mesosphere and lower thermosphere region.
Highlights
Atmospheric gravity waves represent a class of atmosphere oscillations where buoyancy is the restoring force
Longperiod oscillations seen in the airglow brightness on 3–4 and 6–7 November keograms indicated by the red ellipses are associated with large-scale, long λh gravity waves perturbing the green line layer
There is a good chance the background atmosphere above the observation site is similar to that indicated by SABER (Fig. 4), the temperature might still be influenced by gravity waves once we have averaged only a few profiles
Summary
Atmospheric gravity waves represent a class of atmosphere oscillations where buoyancy is the restoring force. Vargas et al.: Gravity wave activity during the SIMONe–2018 campaign to forcing of large-scale circulation (Fritts and Alexander, 2003; Vincent and Alexander, 2020) This dynamical forcing is most prominent within the mesosphere and lower thermosphere (MLT) at altitudes of typically 50–130 km. Attempts of estimating FM of small-scale, short-period waves using multiple observation platforms such as aircraft, lidar, airglow sounders, radars, and satellites have been done (e.g, Suzuki et al, 2010; Bossert et al, 2015), while Gong et al (2019) and Reichert et al (2019) have relied on lidar, meteor radar, and SABER data to study large-scale, long-period waves perturbing the mesosphere temperature and the winds simultaneously. The main contributions here regard the fraction of observed waves carrying substantial FM with the potential to impart significant changes in the 75–110 km dynamics since we show evidence that most observed waves likely experience dissipation in that region
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