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Open AccessArticle

Estimation of Turbulence Parameters in the Lower Troposphere from ShUREX (2016–2017) UAV Data

1
Université de Toulon, Aix-Marseille University, CNRS IRD, MIO, UM110, 83041 Toulon, France
2
Department of Aerospace Engineering Sciences, University of Colorado, Boulder, CO 80309, USA
3
Research Institute for Sustainable Humanosphere, Kyoto University, Kyoto 611-0011, Japan
*
Author to whom correspondence should be addressed.
Atmosphere 2019, 10(7), 384; https://doi.org/10.3390/atmos10070384
Received: 21 May 2019 / Revised: 24 June 2019 / Accepted: 3 July 2019 / Published: 11 July 2019
Turbulence parameters in the lower troposphere (up to ~4.5 km) are estimated from measurements of high-resolution and fast-response cold-wire temperature and Pitot tube velocity from sensors onboard DataHawk Unmanned Aerial Vehicles (UAVs) operated at the Shigaraki Middle and Upper atmosphere (MU) Observatory during two ShUREX (Shigaraki UAV Radar Experiment) campaigns in 2016 and 2017. The practical processing methods used for estimating turbulence kinetic energy dissipation rate ε and temperature structure function parameter C T 2 from one-dimensional wind and temperature frequency spectra are first described in detail. Both are based on the identification of inertial (−5/3) subranges in respective spectra. Using a formulation relating ε and C T 2 valid for Kolmogorov turbulence in steady state, the flux Richardson number R f and the mixing efficiency χ m are then estimated. The statistical analysis confirms the variability of R f and χ m around ~ 0.13 0.14 and ~ 0.16 0.17 , respectively, values close to the canonical values found from some earlier experimental and theoretical studies of both the atmosphere and the oceans. The relevance of the interpretation of the inertial subranges in terms of Kolmogorov turbulence is confirmed by assessing the consistency of additional parameters, the Ozmidov length scale L O , the buoyancy Reynolds number R e b , and the gradient Richardson number Ri. Finally, a case study is presented showing altitude differences between the peaks of N 2 , C T 2 and ε , suggesting turbulent stirring at the margin of a stable temperature gradient sheet. The possible contribution of this sheet and layer structure on clear air radar backscattering mechanisms is examined. View Full-Text
Keywords: turbulence; energy dissipation rate; temperature structure function; eddy diffusivity; outer scale; mixing efficiency; Ozmidov length scale; Kolmogorov turbulence turbulence; energy dissipation rate; temperature structure function; eddy diffusivity; outer scale; mixing efficiency; Ozmidov length scale; Kolmogorov turbulence
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Luce, H.; Kantha, L.; Hashiguchi, H.; Lawrence, D. Estimation of Turbulence Parameters in the Lower Troposphere from ShUREX (2016–2017) UAV Data. Atmosphere 2019, 10, 384.

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