English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

We analyze offshore wind speeds with a time resolution of one second over along period of 20 months for different heights above the sea level. Energyspectra extending over more than seven decades give a comprehensive picture ofwind fluctuations, including intermittency effects at small length scales andsynoptic weather phenomena at large scales. The spectra $S(f)$ show a scalingbehavior 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 $f_{\rm\scriptscriptstyle2D}$, a rapid rise of $fS(f)$ occurs. An analysis of the third-order structurefunction $D_3(\tau)$ of wind speed differences for a given time lag $\tau$shows a rapid change from negative to positive values of $D_3(\tau)$ at$\tau\simeq 1/f_{\rm\scriptscriptstyle 2D}$. Remarkably, after applyingTaylor's hypothesis locally, we find the third-order structure function toexhibit a behavior very similar to that obtained previously from aircraftmeasurements at much higher altitudes in the atmosphere. In particular, thethird-order structure function grows linearly with the separation distance fornegative $D_3$, and with the third power for positive $D_3$. This allows us toestimate energy and enstrophy dissipation rates for offshore wind. Thecrossover from negative to positive values occurs at about the same separationdistance of 400 km as found from the aircraft measurements, suggesting thatthis length is independent of the altitude in the atmosphere.

Signatures of geostrophic turbulence in power spectra and third-order-structure function of offshore wind speed fluctuation