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The WPR-LQ-7 is a UHF (1.3575 GHz) wind profiler radar used for routine measurements of the lower troposphere at Shigaraki Middle and Upper (MU) observatory (34.85° N, 136.10° E, Japan) at a vertical resolution of 100 m and a time resolution of 10 min. Following studies carried out with the 46.5 MHz Middle and Upper atmosphere (MU) radar (Luce et al., 2018), we tested models used to estimate turbulence kinetic energy (TKE) dissipation rates ε from the Doppler spectral width in the altitude range ~0.7 to 4.0 km ASL. For this purpose, we compared LQ-7-derived ε by using processed data available on line (http://www.rish.kyoto-u.ac.jp/radar-group/blr/shigaraki/data/) with direct estimates of ε (εU) from DataHawk UAVs. The statistical results reveal the same trends as reported by Luce et al. (2018) with the MU radar, namely: (1) The simple formulation based on dimensional analysis εLout=σ3 / Lout, with Lout ~70 m, provides the best statistical agreement with εU. (2) The model εN predicting a σ2 N law (N is Brunt-Vaïsälä frequency) for stably stratified conditions tends to overestimate for εU < ~5 10−4 m2 s−3 and to underestimate for εU > ~5 10−4 m2 s−3. We also tested a model εS predicting a σ2 S law (S is the vertical shear of horizontal wind) supposed to be valid for low Richardson numbers (Ri = N2 ⁄ S2). From the case study of a turbulent layer produced by a Kelvin-Helmholtz instability, we found that εS and εLout are both very consistent with εU, while εN underestimates εU in the core of the turbulent layer where N is minimum. We also applied the Thorpe method from data collected from a nearly simultaneous radiosonde and tested an alternative interpretation of the Thorpe length in terms of the Corrsin scale defined for weakly stratified turbulence. A statistical analysis showed that εS also provides better statistical agreement with εU and is much less biased than εN. Combining estimates of N and shear from DataHawk and radar data, respectively, a rough estimate of the Richardson number at a vertical resolution of 100 m (Ri100) was obtained. We performed a statistical analysis on the Ri dependence of the models. The main outcome is that εS compares well with εU for low Ri100's (Ri100 < ~1) while εN fails. εLout varies as εS with Ri100 so that εLout remains the best (and simplest) model in the absence of information on Ri. Also, σ appears to vary as Ri100−1/2 when Ri100 > ~0.4 and shows a degree of dependence with S100 otherwise.

Kelvin Helmholtz tube and knot (KH T/K) dynamics are a subclass of 3D shear instabilities that form when vortex "tubes" and "knots" connect adjacent, misaligned KH billows in a shear layer. While the existence of KH T/K was demonstrated in laboratory experiments by Thorpe 1987, they have only recently been observed in airglow images in the atmosphere (Hecht et al., 2021). Modeling studies by Fritts et al., 2021 determined that tubes and knots yield accelerated vorticity evolution and elevated dissipation rates in KH shear turbulence events, suggesting significant impacts to local mixing anywhere KH T/K dynamics occur. In this study, we present modeling results of T/K dynamics accompanying a thermospheric KH event captured by the 2018 Super Soaker campaign (Mesquita et al., 2020). Chemical tracers released by a rocketsonde on 26 January 2018 showed a coherent KH instability near 102 km that rapidly deteriorated within 45-90 s. Using wind and temperature data from the event, we conducted high resolution DNS employing both wide and narrow spanwise domains to facilitate (wide domain case) and prohibit (narrow domain case) the axial deformation of KH billows that allows tubes and knots to form. KH T/K dynamics are shown to produce accelerated instability evolution consistent with the observations, achieving peak dissipation rates 2.5 times larger and 2.4 buoyancy periods faster than in the case prohibiting T/K. The results suggest that enhanced mixing from thermospheric KH T/K events could account for the discrepancy between modeled and observed vertical eddy diffusion in the lower thermosphere (Liu 2021; Garcia et al., 2014) and merits further study. References:Fritts et al., 2021: https://doi.org/10.1029/2020JD033412 Garcia et al., 2014: https://doi.org/10.1002/2013JD021208 Hecht et al., 2021: https://doi.org/10.1029/2020JD033414 Liu 2021: https://doi.org/10.1029/2020GL091474Mesquita et al., 2020: https://doi.org/10.1029/2020JA027972 Thorpe 1987: https://doi.org/10.1029/JC092iC05p05231

During the SOUTHTRAC-GW (Southern hemisphere Transport, Dynamics and Chemistry – Gravity Waves) field campaign, gravity waves above the Southern Andes mountains, the Drake passage and the Antarctic Peninsula were probed with airborne instruments onboard the HALO research aircraft. The Airborne Lidar for Middle Atmosphere research (ALIMA) detected particularly strong mountain waves in excess of 25 K amplitude in cross-mountain legs above the Southern Andes of research flight ST08 on 12 September 2019. The mountain waves propagated well into the mesosphere up to 65 km altitude with possible generation of smaller-scale secondary waves during wave breaking above 65 km. A superposition of mountain waves with horizontal wavelengths in the range 15-200 km and vertical wavelengths 7-24 km dominated the wave field between 18 and 65 km altitude. Vertical wavelengths predicted by the hydrostatic equation and horizontal wind from the European Center for Medium-Range Weather Forecasts’ Integrated Forecasting System are in good agreement with observed vertical wavelengths. We apply wavelet analysis to the measured temperature field along the flight track in order to identify and separate dominant scales, and estimate their relative contributions to the total gravity wave momentum flux as well as the local and zonal-mean gravity wave drag. Furthermore, we compare our observations to results obtained by Fourier ray analysis of the terrain of the Southern Andes. The Fourier model allows the investigation of the 3d-wave field and trapped waves which are not well sampled by the ALIMA instrument because of the relative alignment between the wave fronts and the flight track. These sampling biases are quantified from virtual flights through the model domain at multiple angles and taken into account in the estimation of the total momentum flux derived from ALIMA observations. The combination of high-resolution observations and model data reveals the significance of this and similar mountain wave events in the Southern Andes region for the atmospheric dynamics at ~60° S.

The southern part of South America and the Antarctic peninsula are known as the world’s strongest hotspot region of stratospheric gravity wave (GW) activity. Large tropospheric winds are deflected by the Andes and the Antarctic Peninsula and excite GWs that might propagate into the upper mesosphere. Satellite observations show large stratospheric GW activity above the mountains, the Drake Passage, and in a belt centered along 60°S. This scientifically highly interesting region for studying GW dynamics was the focus of the Southern Hemisphere Transport, Dynamics, and Chemistry–Gravity Waves (SOUTHTRAC-GW) mission. The German High Altitude and Long Range Research Aircraft (HALO) was deployed to Rio Grande at the southern tip of Argentina in September 2019. Seven dedicated research flights with a typical length of 7,000 km were conducted to collect GW observations with the novel Airborne Lidar for Middle Atmosphere research (ALIMA) instrument and the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) limb sounder. While ALIMA measures temperatures in the altitude range from 20 to 90 km, GLORIA observations allow characterization of temperatures and trace gas mixing ratios from 5 to 15 km. Wave perturbations are derived by subtracting suitable mean profiles. This paper summarizes the motivations and objectives of the SOUTHTRAC-GW mission. The evolution of the atmospheric conditions is documented including the effect of the extraordinary Southern Hemisphere sudden stratospheric warming (SSW) that occurred in early September 2019. Moreover, outstanding initial results of the GW observation and plans for future work are presented., Facultad de Ciencias Astronómicas y Geofísicas

At the end of the austral winter 2019, a sudden stratospheric warming led to an early breakdown of the polar vortex. The meteorological conditions during this event are documented and analysed by means of operational analyses of the Intgrated Forecast System (IFS) of the ECMWF and ERA5 data. Especially, we focus on the decline of stratospheric wave activity over the southern tip of South America. For this region, ground-based and airborne measurements are employed to compare selected diagnostics with fields from the ECMWF's numerical weather prediction model IFS. Furthmore, the meteorological conditions for one selected research flight during the SOUTHTRAC campaign are presented. This part serves as background information for a case study presented by Tyler Mixa.

We present observations by airborne lidar which were obtained over the southern Andes during the SOUTHTRAC campaign in September 2019. Operated onboard the German research aircraft HALO, the Airborne LIdar for Middle Atmosphere research (ALIMA) acquired high resolution temperature profiles in the altitude range 20-80 km. The data show signatures of mountain waves located at the mountain ridges, but often these signatures also extend several hundred kilometer downstream. While during the first days of the campaign mountain waves were able to penetrate into the mesosphere, observations obtained in the following weeks indicate a downward shift of the breaking zone from the mesosphere to the stratosphere which is consistent with the early breakdown of the polar vortex. Our data also indicate evidence for generation of secondary gravity waves within the breaking zone of the mountain waves.

We present numerical simulations of a deep orographic gravity wave (GW) event observed by the ALIMA airborne lidar on 11-12 September 2019 over Southern Argentina. The measurements are taken from the 2019 SOUTHTRAC Campaign, employing a comprehensive suite of remote sensing and in-situ instruments onboard the HALO research aircraft to study the stratospheric GW hotspot over Tierra del Fuego and the Antarctic Peninsula. Wind conditions on 11-12 September exhibit local and large-scale directional shear from the ground to the polar night jet, creating a complex propagation environment supporting multiple orientations of GW propagation and strong potential for local GW breaking and secondary GW generation. Using high resolution numerical models, we simulate the 3D evolution of the orographic GW field to analyze the remote sensing and in-situ measurements from the event.

The region around Southern Argentina and the Antarctic peninsula is known as the world’s strongest hotspot of stratospheric gravity wave activity. In this region, large tropospheric winds are perturbed by the orography of the Andes and the Antarctic peninsula resulting in the excitation of mountain waves which might propagate all the way up into the upper mesosphere when the polar night jet is intact. In addition, satellite observations also show large stratospheric wave activity in the region of the Drake passage, i.e., in between the Andes and the Antarctic peninsula, and along the corresponding latitudinal circle of 60°S. The origin of these waves is currently not entirely understood. Several hypotheses are currently being investigated, like for example the idea that the mountain waves that were originally excited over the Andes and the Antarctic peninsula propagate horizontally to 60°S and along the latitudinal circle. In order to investigate this and other hypotheses the German research aircraft HALO was deployed to Rio Grande, Tierra del Fuego, at the Southern Tip of Argentina in September and November 2019 in the frame of the SOUTHTRAC (Southern hemisphere Transport, Dynamics, and Chemistry) research mission. A total of 6 dedicated research flights with a typical length of 7000km were conducted to obtain gravity wave observations with the newly developed ALIMA (ALIMA=Airborne LIdar for Middle Atmosphere research)-instrument and the GLORIA (GLORIA=Gimballed Limb Observer for Radiance Imaging of the Atmosphere) limb sounder. While ALIMA measures temperatures and temperature perturbations in the altitude range from 20-90 km, GLORIA observations allow to characterize wave perturbations in temperatures and trace gas concentrations below flight level (

International audience; The ShUREX (Shigaraki UAV Radar Experiment) 2015 campaign carried out at the Shigaraki Middle and Upper atmosphere (MU) observatory (Japan) in June 2015 provided a unique opportunity to compare vertical profiles of atmospheric parameters estimated from unmanned aerial vehicle (UAV), balloon, and radar data in the lower troposphere. The present work is intended primarily as a demonstration of the potential offered by combination of these three instruments for studying the small-scale structure and dynamics in the lower troposphere. Here, we focus on data collected almost simultaneously by two instrumented UAVs and two meteorological balloons, near the MU radar operated continuously during the campaign. The UAVs flew along helical ascending and descending paths at a nearly constant horizontal distance from the radar ( 1.0 km), while the balloons launched from the MU radar site drifted up to 3-5 km in the altitude range of comparisons ( 0.5 to 4.0 km) due to wind advection. Vertical profiles of squared Brünt-Väisälä frequency N 2 and squared vertical gradient of generalized potential refractive index M 2 were estimated at a vertical resolution of 20 m from pressure, temperature, and humidity data collected by UAVs and radiosondes. Profiles of M 2 were also estimated from MU radar echo power at vertical incidence at a vertical sampling of 20 m and various time resolutions (1-4 min). The balloons and the MU radar provided vertical profiles of wind and wind shear S so that two independent estimates of the gradient Richardson number ( Ri = N 2/ S 2) could be obtained at a range resolution of 150 m. The two estimates of Ri profiles also showed remarkable agreement at all altitudes. We show that all three instruments detected the same prominent temperature and humidity gradients, down to decameter scales in stratified conditions. These gradients extended horizontally over a few kilometers at least and persisted for hours without significant changes, indicating that the turbulent diffusion was weak . Large discrepancies between N 2and M 2 profiles derived from the balloon, UAV, and radar data were found in a turbulent layer generated by a Kelvin-Helmholtz (KH) shear flow instability in the height range from 1.80 to 2.15 km. The cause of these discrepancies appears to depend on the stage of the KH billows.

Mountain wave (MW) propagation and dynamics extending into the upper mesosphere accompanying weak forcing are examined using in situ and remote‐sensing measurements aboard the National Science Foundation/National Center for Atmospheric Research Gulfstream V (GV) research aircraft and the German Aerospace Center Falcon. The measurements were obtained during Falcon flights FF9 and FF10 and GV Research Flight RF22 of the Deep Propagating Gravity Wave Experiment (DEEPWAVE) performed over Mount Cook, New Zealand, on 12 and 13 July 2014. In situ measurements revealed both trapped lee waves having zonal wavelengths of λₓ ~ 12 km and less, and larger‐scale, vertically propagating MWs primarily at λₓ ~ 20–60 km and ~100–300 km extending from west to ~400 km east of Mount Cook. GV Rayleigh lidar measurements from 25‐ to 60‐km altitudes showed that the weak forcing and zonal winds that increased from ~12 m/s at 12 km to ~40 and 130 m/s at 30 and 55 km, respectively, enabled largely linear MW propagation and strong amplitude growth with altitude into the mesosphere. GV Na lidar and airglow imager measurements revealed an extensive MW response from ~70 to 87 km with large amplitudes and vertical displacements at λₓ ~ 40–300 km but with both decreasing with altitude approaching a critical level near 90 km. These MWs exhibited large‐scale MW breaking and among the largest sustained momentum fluxes observed in the mesosphere. UK Met Office Unified Model simulations of the RF22 MW event captured many aspects of the observed MW field and revealed that despite the dominant large‐scale MW responses in the stratosphere, the major momentum fluxes accompanied smaller‐scale waves.

The Deep Propagating Gravity Wave Experiment (DEEPWAVE) was designed to quantify gravity wave (GW) dynamics and effects from orographic and other sources to regions of dissipation at high altitudes. The core DEEPWAVE field phase took place from May through July 2014 using a comprehensive suite of airborne and ground-based instruments providing measurements from Earth’s surface to ∼100 km. Austral winter was chosen to observe deep GW propagation to high altitudes. DEEPWAVE was based on South Island, New Zealand, to provide access to the New Zealand and Tasmanian “hotspots” of GW activity and additional GW sources over the Southern Ocean and Tasman Sea. To observe GWs up to ∼100 km, DEEPWAVE utilized three new instruments built specifically for the National Science Foundation (NSF)/National Center for Atmospheric Research (NCAR) Gulfstream V (GV): a Rayleigh lidar, a sodium resonance lidar, and an advanced mesosphere temperature mapper. These measurements were supplemented by in situ probes, dropsondes, and a microwave temperature profiler on the GV and by in situ probes and a Doppler lidar aboard the German DLR Falcon. Extensive ground-based instrumentation and radiosondes were deployed on South Island, Tasmania, and Southern Ocean islands. Deep orographic GWs were a primary target but multiple flights also observed deep GWs arising from deep convection, jet streams, and frontal systems. Highlights include the following: 1) strong orographic GW forcing accompanying strong cross-mountain flows, 2) strong high-altitude responses even when orographic forcing was weak, 3) large-scale GWs at high altitudes arising from jet stream sources, and 4) significant flight-level energy fluxes and often very large momentum fluxes at high altitudes.

For the first time, the performance of the range imaging technique of the very high frequency band middle and upper atmosphere (MU) radar (Shigaraki observatory, Japan), when using frequency diversity, is assessed. This is done by the detection of unmanned aerial vehicles (UAVs) operated near the radar during the Shigaraki UAV radar experiment campaign, carried out from June 1, 2015 to June 14, 2015. During this campaign devoted to the measurements of fine-scale turbulence and stability in the lower troposphere using the turbulence sensors on the DataHawk UAV and the MU radar, the detection of the small UAV by the MU radar provided an excellent opportunity for taking stock of the range imaging technique in the presence of a single hard target. It was found that range imaging reproduces a faithful image of the aircraft position and its displacements with an excellent accuracy (of the order of ~10 m), giving extra credence to the thin echo layers and their vertical displacements generally observed from the range imaging technique in stably stratified conditions.

15th MST Radar WorkshopSession M4: MST Radar scattering, turbulence and small-scale processesMay 30 (Tue), Poster Session

15th MST Radar WorkshopSession M4: MST Radar scattering, turbulence and small-scale processesMay 30 (Tue), Poster Session

15th MST Radar WorkshopSession M4: MST Radar scattering, turbulence and small-scale processesMay 30 (Tue), Poster Session

The Shigaraki unmanned aerial vehicle (UAV)-Radar Experiment (ShUREX) is an international (USA-Japan-France) observational campaign, whose overarching goal is to demonstrate the utility of small, lightweight, inexpensive, autonomous UAVs in probing and monitoring the lower troposphere and to promote synergistic use of UAVs and very high frequency (VHF) radars. The 2-week campaign lasting from June 1 to June 14, 2015, was carried out at the Middle and Upper Atmosphere (MU) Observatory in Shigaraki, Japan. During the campaign, the DataHawk UAV, developed at the University of Colorado, Boulder, and equipped with high-frequency response cold wire and pitot tube sensors (as well as an iMET radiosonde), was flown near and over the VHF-band MU radar. Measurements in the atmospheric column in the immediate vicinity of the radar were obtained. Simultaneous and continuous operation of the radar in range imaging mode enabled fine-scale structures in the atmosphere to be visualized by the radar. It also permitted the UAV to be commanded to sample interesting structures, guided in near real time by the radar images. This overview provides a description of the ShUREX campaign and some interesting but preliminary results of the very first simultaneous and intensive probing of turbulent structures by UAVs and the MU radar. The campaign demonstrated the validity and utility of the radar range imaging technique in obtaining very high vertical resolution (~20 m) images of echo power in the atmospheric column, which display evolving fine-scale atmospheric structures in unprecedented detail. The campaign also permitted for the very first time the evaluation of the consistency of turbulent kinetic energy dissipation rates in turbulent structures inferred from the spectral broadening of the backscattered radar signal and direct, in situ measurements by the high-frequency response velocity sensor on the UAV. The data also enabled other turbulence parameters such as the temperature structure function parameter CT2 and refractive index structure function parameter Cn2 to be measured by sensors on the UAV, along with radar-inferred refractive index structure function parameter Cn, radar2. The comprehensive dataset collected during the campaign (from the radar, the UAV, the boundary layer lidar, the ceilometer, and radiosondes) is expected to help obtain a better understanding of turbulent atmospheric structures, as well as arrive at a better interpretation of the radar data., The Correction to this article has been published in Progress in Earth and Planetary Science 2018 5:48