Comparisons between high-resolution profiles of squared refractive index gradient &amp;lt;i&amp;gt;M&amp;lt;/i&amp;gt;&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt; measured by the Middle and Upper  Atmosphere Radar and unmanned aerial vehicles (UAVs) during the Shigaraki UAV-Radar Experiment 2015 campaign

Lawrence

et al. 2017

Prog Earth Planet Sci

Self Cite

The Shigaraki unmanned aerial vehicle (UAV)-Radar Experiment (ShUREX) is an international (USA-JapanFrance) 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 highfrequency response velocity sensor on the UAV. The data also enabled other turbulence parameters such as the temperature structure function parameter C 2 T and refractive index structure function parameter C 2 n to be measured by sensors on the UAV, along with radar-inferred refractive index structure function parameter C 2 n;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.

Section: Shurex 2015 Campaignmentioning

confidence: 99%

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

Lawrence

et al. 2017

Prog Earth Planet Sci

Self Cite

“…The discrepancies in the KH turbulent layer could be partly due to the horizontal scale of KH billows, found to be of the order of, or even smaller than, the horizontal distance between the measurements made by the three instruments. The present work describes in detail, the characteristics of the various profiles in such conditions and complements the discussion presented by Luce et al (2017) based on M 2 comparisons only. The layout of the paper is as follows.…”

Section: Introductionmentioning

confidence: 60%

“…Luce et al (2001b) described the principle of the technique that became operational on the MU radar in 2004 after upgrades (Luce et al 2006). Profiles of M 2 were estimated from P MU at vertical incidence at a vertical sampling of 20 m using the theoretical derivations and practical methods already described by Luce et al (2017). Basically, the M 2 profiles were estimated from the average of P MU over 1 and 4 min, along the time-height position of the UAVs (shown by the red lines in Fig.…”

Section: Balloonsmentioning

confidence: 99%

“…Luce et al (2018) took advantage of the UAV echoes in the MU radar Doppler spectra for an ultimate validation and evaluation of a frequency domain interferometry technique used to improve the range resolution of the radar. Luce et al (2017) compared profiles of the squared generalized potential refractive index gradient M 2 (Ottersten 1969) derived from pressure, temperature, and humidity (PTU) data collected by the UAVs with those derived from MU radar echo power by using a model based on partial reflection mechanism. They concluded that the MU radar provides faithful highresolution profiles of the vertical temperature and humidity gradients down to decameter scale, at a time resolution of only a few tens of seconds, in at least stratified and clear air conditions.…”

Section: Introductionmentioning

confidence: 99%

“…In the present work, additional comparisons of atmospheric parameters are presented by including balloon data not presented in Luce et al (2017). The balloons were launched at the MU radar observatory site almost simultaneously to the flights of two UAVs, at a time interval of about 2 h on 07 June 2015.…”

Section: Introductionmentioning

confidence: 99%

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

Hashiguchi

et al. 2018

Prog Earth Planet Sci

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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 2 and 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.

Turbulence kinetic energy dissipation rates estimated from concurrent UAV and MU radar measurements

Hashiguchi

et al. 2018

Earth Planets Space

Self Cite

We tested models commonly used for estimating turbulence kinetic energy dissipation rates ε from very high frequency stratosphere-troposphere radar data. These models relate the root-mean-square value σ of radial velocity fluctuations assessed from radar Doppler spectra to ε. For this purpose, we used data collected from the middle and upper atmosphere (MU) radar during the Shigaraki unmanned aerial vehicle (UAV)-radar experiment campaigns carried out at the Shigaraki MU Observatory, Japan, in June 2016 and 2017. On these occasions, UAVs equipped with fastresponse and low-noise Pitot tube sensors for turbulence measurements were operated in the immediate vicinity of the MU radar. Radar-derived dissipation rates ε estimated from the various models at a range resolution of 150 m from the altitude of 1.345 km up to the altitude of ~ 4.0 km, a (half width half power) beam aperture of 1.32° and a time resolution of 24.6 s, were compared to dissipation rates (ε U) directly obtained from relative wind speed spectra inferred from UAV measurements. Firstly, statistical analysis results revealed a very close relationship between enhancements of σ and ε U for ε U 10 −5 m 2 s −3 , indicating that both instruments detected the same turbulent events with ε U above this threshold. Secondly, ε U was found to be statistically proportional to σ 3 , whereas a σ 2 dependence is expected when the size of the largest turbulent eddies is smaller than the longitudinal and transverse dimensions of the radar sampling volume. The σ 3 dependence was found even after excluding convectively generated turbulence in the planetary boundary layer and below clouds. The best agreement between ε U and radar-derived ε was obtained with the simple formulation based on dimensional analysis ε = σ 3 /L c where L C ≈ 50-70 m. This empirical expression constitutes a simple way to estimate dissipation rates in the lower troposphere from MU radar data whatever the sources of turbulence be, in clear air or cloudy conditions, consistent with UAV estimates.