The Share of the Mean Turbulent Kinetic Energy in the Near-Neutral Surface Layer for High and Low Wind Speeds

• Published in: Boundary-layer meteorology Vol. 172; no. 1; pp. 81 - 106
• Main Authors: Schiavon, M., Tampieri, F., Bosveld, F. C., Mazzola, M., Castelli, S. Trini, Viola, A. P., Yagüe, C.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.07.2019; Springer; Springer Nature B.V
• Subjects: Analysis; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Closures; Components; Dependence; Earth and Environmental Science; Earth Sciences; Environmental conditions; Force and energy; Kinetic energy; Low wind speeds; Meteorology; Modelling; Research Article; Reynolds averaging; Spectral analysis; Stability; Surface boundary layer; Surface layers; Turbulent kinetic energy; Velocity; Wind; Wind speed; Low wind speed; Turbulent kinetic energy; Submeso motions; Velocity spectra; Dissipation rate
• ISSN: 0006-8314; 1573-1472
• DOI: 10.1007/s10546-019-00435-6

We examine the dependence on wind speed of the share of the mean turbulent kinetic energy among the three velocity components in the near-neutral surface layer. To contrast the general behaviour and the local effects, four datasets are considered, corresponding to different surfaces and environmental conditions. For high wind speeds (i.e., wind speed ≈ 10 ms - 1 ), the shares are well-defined and about the same for all sites. As wind speed decreases (becoming ≈ 1 ms - 1 ), large record-to-record variability occurs giving, on average, an almost isotropic state for the horizontal velocity components. Through spectral analysis, we relate this behaviour to the low-frequency, submeso motions and to the lack of conditions required by Reynolds averaging. The implications for modelling are also discussed, showing that the wind speed, or a related quantity, must be accounted for, besides stability, in second-order closures.