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Boundary-Layer Meteorology

, Volume 156, Issue 1, pp 53–71 | Cite as

Wind Statistics from a Forested Landscape

  • Johan Arnqvist
  • Antonio Segalini
  • Ebba Dellwik
  • Hans Bergström
Article

Abstract

An analysis and interpretation of measurements from a 138-m tall tower located in a forested landscape is presented. Measurement errors and statistical uncertainties are carefully evaluated to ensure high data quality. A 40\(^\circ \) wide wind-direction sector is selected as the most representative for large-scale forest conditions, and from that sector first-, second- and third-order statistics, as well as analyses regarding the characteristic length scale, the flux-profile relationship and surface roughness are presented for a wide range of stability conditions. The results are discussed with focus on the validity of different scaling regimes. Significant wind veer, decay of momentum fluxes and reduction in shear length scales with height are observed for all stability classes, indicating the influence of the limited depth of the boundary layer on the measured profiles. Roughness sublayer characteristics are however not detected in the presented analysis. Dimensionless gradients are shown to follow theoretical curves up to 100 m in stable conditions despite surface-layer approximations being invalid. This is attributed to a balance of momentum decay and reduced shear length scale growth with height. The wind profile shows a strong stability dependence of the aerodynamic roughness length, with a 50 % decrease from neutral to stable conditions.

Keywords

Above-canopy turbulence statistics Atmospheric boundary layer  Roughness length Surface-layer scaling  Wind power 

Notes

Acknowledgments

This work is part of Vindforsk III, a research program sponsored by the Swedish Energy Agency. Vattenfall Vindkraft AB is greatly acknowledged for making their data available for the present work.

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Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  • Johan Arnqvist
    • 1
  • Antonio Segalini
    • 2
  • Ebba Dellwik
    • 3
  • Hans Bergström
    • 1
  1. 1.Department of Earth Sciences, MeteorologyUppsala UniversityUppsalaSweden
  2. 2.Linné FLOW CentreKTH MechanicsStockholmSweden
  3. 3.DTU Wind EnergyTechnical University of DenmarkRoskildeDenmark

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