Title:	Signatures of geostrophic turbulence in power spectra and third-order structure function of offshore wind speed fluctuations
Authors:	Sim, So‑Kumneth Peinke, Joachim Maass, Philipp
ORCID of the author:	https://orcid.org/0000-0001-7921-5087 https://orcid.org/0000-0002-0775-7423 https://orcid.org/0000-0002-1268-8688
Abstract:	We analyze offshore wind speeds with a time resolution of one second over a long period of 20 months for different heights above the sea level. Energy spectra extending over more than seven decades give a comprehensive picture of wind fluctuations, including intermittency effects at small length scales and synoptic weather phenomena at large scales. The spectra S(f) show a scaling behavior consistent with three-dimensional turbulence at high frequencies f, followed by a regime at lower frequencies, where fS(f) varies weakly. Lowering the frequency below a crossover frequency , a rapid rise of fS(f) occurs. An analysis of the third-order structure function of wind speed differences for a given time lag shows a rapid change from negative to positive values of at . Remarkably, after applying Taylor’s hypothesis locally, we find the third-order structure function to exhibit a behavior very similar to that obtained previously from aircraft measurements at much higher altitudes in the atmosphere. In particular, the third-order structure function grows linearly with the separation distance for negative , and with the third power for positive . This allows us to estimate energy and enstrophy dissipation rates for offshore wind. The crossover from negative to positive values occurs at about the same separation distance of 400 km as found from the aircraft measurements, suggesting that this length is independent of the altitude in the atmosphere.
Citations:	Sim, SK., Peinke, J. & Maass, P.: Signatures of geostrophic turbulence in power spectra and third-order structure function of offshore wind speed fluctuations. Sci Rep 13, 13411 (2023)
URL:	https://doi.org/10.48693/519 https://osnadocs.ub.uni-osnabrueck.de/handle/ds-2024022810948
Subject Keywords:	Environmental sciences; Physics
Issue Date:	17-Aug-2023
License name:	Attribution 4.0 International
License url:	http://creativecommons.org/licenses/by/4.0/
Type of publication:	Einzelbeitrag in einer wissenschaftlichen Zeitschrift [Article]
Appears in Collections:	FB06 - Hochschulschriften Open-Access-Publikationsfonds

This item is licensed under a Creative Commons License