Atmospheric Mesoscale Spectra and Structure Functions of Mean Horizontal Velocity Fluctuations Measured with a Doppler Sodar Network

M. Masmoudi CNET/CRPE/CNRS, Issy les Moulineaux, France

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A. Weill CNET/CRPE/CNRS, Issy les Moulineaux, France

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Abstract

Analyses of mean horizontal wind speed from four Doppler sodars separated by 15 to 38 km in the Gers region during the Mesogers 84 experiment gave information on the horizontal wind speed spectral behavior of the so-called mesoscale turbulence during 3 days of fair weather situations. The −5/3; spectral behavior is obtained. A study of the validity of the Taylor hypothesis at this scale shows that for the scales that are considered, this hypothesis is reasonable, but poses difficult questions about the transport speed, which seems to be close to the mean wind speed spatially averaged over the four sodars.

Vorticity spectra are found to support a vortical mode related to quasi-two-dimensional turbulence rather than due to purely internal inertia-gravity wave interactions.

Abstract

Analyses of mean horizontal wind speed from four Doppler sodars separated by 15 to 38 km in the Gers region during the Mesogers 84 experiment gave information on the horizontal wind speed spectral behavior of the so-called mesoscale turbulence during 3 days of fair weather situations. The −5/3; spectral behavior is obtained. A study of the validity of the Taylor hypothesis at this scale shows that for the scales that are considered, this hypothesis is reasonable, but poses difficult questions about the transport speed, which seems to be close to the mean wind speed spatially averaged over the four sodars.

Vorticity spectra are found to support a vortical mode related to quasi-two-dimensional turbulence rather than due to purely internal inertia-gravity wave interactions.

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