Complex Dynamics of High Frequency Atmospheric Gravity Wave and Fine Structure Interactions

Gravity waves are a dominant source of energy transport and coupling throughout the atmosphere. Transient gravity wave propagation effects and locally induced dissipation make significant contributions to the variability of temperature and wind evolutions over a broad range of spatial and temporal scales. Gravity wave impacts are particularly important to the mesosphere and lower thermosphere, where high wave amplitudes promote a range of complex, nonlinear interactions with the background environment at scales that are difficult to model and observe. An improved understanding of small-scale, temporally and spatially intermittent gravity wave interactions with variable local and large-scale environments is essential to improving how gravity wave dynamics are parameterized in mesoscale and global scale models.This dissertation presents a comprehensive overview and analysis of the complex dynamics of high frequency atmospheric gravity wave and fine structure interactions in the mesosphere and lower thermosphere. Simulation studies are carried out to identify the fundamental dynamics of gravity wave-fine structure interactions in an idealized environment, evaluate the behavior of transient gravity wave propagation in an evolving background where linear assumptions break down, and determine the limitations of modeling gravity wave-fine structure interactions with the constraints of current mesoscale models. These studies utilize high resolution numerical simulations and improve the current understanding of gravity wave dynamics and their impact on the atmosphere. Findings in these studies indicate that gravity wave-fine structure interactions have predictable dynamics that can be traced to the underlying vorticity characteristics set by the background environment. Gravity wave interactions with fine-structure background variations below gravity wave scales determine the formation of instability and induced wind characteristics, while gravity wave interactions with time evolving fine-structure variations larger than gravity wave scales account for intermittent forcing characteristics observed in the mesosphere and lower thermosphere. The dominant gradient characteristics of these interactions break down with insufficient spatial resolution, and the time dependent characteristics break down when under-resolved models apply viscous damping to constrain small scale motions. With proper consideration of the expected dynamics in a given environment, one can estimate the extent to which gravity wave-fine structure interactions contribute to the variability in under-resolved model simulations, identifying environments for which improved characterization would be beneficial

The Deep Propagating Gravity Wave Experiment (DEEPWAVE): An airborne and ground-based exploration of gravity wave propagation and effects from their sources throughout the lower and middle atmosphere

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

Nonlinear Simulations of Gravity Wave Tunneling and Breaking over Auckland Island

Large-amplitude gravity wave oscillations were observed directly above and in the lee of the Southern Ocean’s Auckland Island (50.88S, 166.18E) within the mesospheric airglow and sodium layers at ;78–83 km altitudes during research flight RF23 of the Deep Propagating Gravity Wave Experiment (DEEPWAVE

Vertical structure of the lower troposphere derived from MU radar, unmanned aerial vehicle, and balloon measurements during ShUREX 2015

Abstract 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

On the Performance of the Range Imaging Technique Estimated Using Unmanned Aerial Vehicles During the ShUREX 2015 Campaign

International audienc

Correction to: Shigaraki UAV-Radar Experiment (ShUREX): overview of the campaign with some preliminary results

International audienc

Shigaraki UAV-Radar Experiment (ShUREX): overview of the campaign with some preliminary results

International audienceThe 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 CT and refractive index structure function parameter C2n to be measured by sensors on the UAV, along with radar-inferred refractive index structure function parameter C2n,radar. 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

小型無人航空機・MUレーダー同時観測実験

[第322回生存圏シンポジウム ; 第10回MUレーダー・赤道大気レーダーシンポジウム (MU-EAR)] 開催日時: 2016年9月8日(木)-9日(金), 開催場所: 京都大学宇治キャンパス, 主催者: 京都大学生存圏研究