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Annales Geophysicae An open-access journal of the European Geosciences Union
Ann. Geophys., 35, 423-441, 2017
http://www.ann-geophys.net/35/423/2017/
doi:10.5194/angeo-35-423-2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Regular paper
17 Mar 2017
Comparisons between high-resolution profiles of squared refractive index gradient M2 measured by the Middle and Upper Atmosphere Radar and unmanned aerial vehicles (UAVs) during the Shigaraki UAV-Radar Experiment 2015 campaign
Hubert Luce1, Lakshmi Kantha3, Hiroyuki Hashiguchi2, Dale Lawrence3, Masanori Yabuki2, Toshitaka Tsuda2, and Tyler Mixa3 1Université de Toulon, CNRS/INSU, IRD, Mediterranean Institute of Oceanography (MIO), UM 110, La Garde, France
2Research Institute for Sustainable Humanosphere, Kyoto University, Kyoto, Japan
3Department of Aerospace Engineering Sciences, University of Colorado Boulder, Boulder, Colorado, USA
Abstract. New comparisons between the square of the generalized potential refractive index gradient M2, estimated from the very high-frequency (VHF) Middle and Upper Atmosphere (MU) Radar, located at Shigaraki, Japan, and unmanned aerial vehicle (UAV) measurements are presented. These comparisons were performed at unprecedented temporal and range resolutions (1–4 min and  ∼  20 m, respectively) in the altitude range  ∼  1.27–4.5 km from simultaneous and nearly collocated measurements made during the ShUREX (Shigaraki UAV-Radar Experiment) 2015 campaign. Seven consecutive UAV flights made during daytime on 7 June 2015 were used for this purpose. The MU Radar was operated in range imaging mode for improving the range resolution at vertical incidence (typically a few tens of meters). The proportionality of the radar echo power to M2 is reported for the first time at such high time and range resolutions for stratified conditions for which Fresnel scatter or a reflection mechanism is expected. In more complex features obtained for a range of turbulent layers generated by shear instabilities or associated with convective cloud cells, M2 estimated from UAV data does not reproduce observed radar echo power profiles. Proposed interpretations of this discrepancy are presented.

Citation: Luce, H., Kantha, L., Hashiguchi, H., Lawrence, D., Yabuki, M., Tsuda, T., and Mixa, T.: Comparisons between high-resolution profiles of squared refractive index gradient M2 measured by the Middle and Upper Atmosphere Radar and unmanned aerial vehicles (UAVs) during the Shigaraki UAV-Radar Experiment 2015 campaign, Ann. Geophys., 35, 423-441, doi:10.5194/angeo-35-423-2017, 2017.
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Short summary
Results of comparisons between data collected from a VHF Doppler radar and small unmanned aerial vehicles (UAVs) are presented. The UAVs, equipped with meteorological sensors, flew nearby the radar up to an altitude of ~ 4.0 km. Both instruments detected the same clear-air refractive index gradients at a vertical scale of ~ 20 m when the vertical stratification was strong. A VHF radar can thus provide a faithful image of the vertical stratification of the atmosphere down to decimeter scales.
Results of comparisons between data collected from a VHF Doppler radar and small unmanned aerial...
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