Wind Statistics from a Forested Landscape

Johan Arnqvist, Antonio Segalini, Ebba Dellwik, Hans Bergström

Research output: Contribution to journalJournal articleResearchpeer-review

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(Formula presented.) 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.
Original languageEnglish
JournalBoundary-Layer Meteorology
Volume156
Issue number1
Pages (from-to)53-71
Number of pages19
ISSN0006-8314
DOIs
Publication statusPublished - 2015

Keywords

  • Above-canopy turbulence statistics
  • Atmospheric boundary layer
  • Roughness length
  • Surface-layer scaling
  • Wind power
  • Aerodynamic stability
  • Boundary layer flow
  • Boundary layers
  • Measurement errors
  • Quality control
  • Surface roughness
  • Uncertainty analysis
  • Wind effects
  • Aerodynamic roughness length
  • Canopy turbulence
  • Characteristic length
  • Flux-profile relationships
  • Roughness sublayers
  • Statistical uncertainty
  • Surface layers
  • Forestry

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