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Article Dans Une Revue Journal of Atmospheric and Solar-Terrestrial Physics Année : 2014

Energetics of persistent turbulent layers underneath mid-level clouds estimated from concurrent radar and radiosonde data

Résumé

Two Japanese-French field campaigns devoted to studying small-scale turbulence and instabilities in the lower atmosphere were conducted in September 2011 and November 2012 at the Shigaraki Middle and Upper atmosphere (MU) Observatory (34.85°N, 136.15°E; Japan). The Very High Frequency Middle and Upper atmosphere radar (MUR) was operated with a time resolution of the order of 10 s in range imaging mode allowing echo power measurements at fine range-resolutions (typically, a few tens of meters). In addition, balloons instrumented with RS92G Vaisala radiosondes were launched from the observatory during the radar operations. From the raw data of temperature, pressure and humidity, temperature turbulent layers can be identified from the detection of overturns by using the Thorpe method (1977). During the two campaigns, both radar and balloon data revealed turbulent layers of about 1.0 km in depth, underneath mid-level clouds and meteorological frontal zones. They persisted for about 10 hours in the radar data. The balloon data collected were undoubtedly representative of the conditions met by the radar. Turbulence parameters associated with stably stratified flows were tentatively estimated by using different methods involving both radar and balloon observations for 4 balloon flights. These parameters included the Thorpe, buoyancy, and Ozmidov scales LT, LB and LO, potential and kinetic turbulent energies TPE and TKE, potential kinetic energy dissipation rates ϵP and ϵK and tubulent diffusivities Kθ. The turbulence scales were found to be consistent between each other within a factor of about 2. Energy dissipation rates of 0.6 mW/kg were found for 3 cases and 0.06 mW/kg for one case.
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hal-00933074 , version 1 (19-01-2014)

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Richard Wilson, Hubert Luce, H. Hashiguchi, N. Nishi, Y. Yabuki. Energetics of persistent turbulent layers underneath mid-level clouds estimated from concurrent radar and radiosonde data. Journal of Atmospheric and Solar-Terrestrial Physics, 2014, 118, pp.78-89. ⟨10.1016/j.jastp.2014.01.005⟩. ⟨hal-00933074⟩
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