Boundary-Layer Meteorology

, Volume 103, Issue 2, pp 227–251

Mechanisms Controlling Turbulence Development Across A Forest Edge

  • A.P. Morse
  • B.A. Gardiner
  • B.J. Marshall
Article

DOI: 10.1023/A:1014507727784

Cite this article as:
Morse, A., Gardiner, B. & Marshall, B. Boundary-Layer Meteorology (2002) 103: 227. doi:10.1023/A:1014507727784

Abstract

In this paper we discuss the development of turbulence back from the transition fromopen moorland to a forest. Data from a field study and a wind-tunnel experiment arepresented. These show that the variance in the streamwise velocity begins to adjust tothe new surface between 2 to 4 tree heights downwind of the transition. This is soonerthan either the vertical velocity variance or the shear stress, both of which begin to adjust in a zone 3 to 5 tree heights downwind of the edge. Key terms in the prognostic equations for streamwise and vertical velocity variance are evaluated in order to explain these differences. The flow distortion caused by the forest edge, which extends to 4 tree heights downwind of the forest edge, is shown to be crucial in the delayed turbulence development. Initially the shear production term, which is the dominant source for the streamwise velocity variance, is counteracted by a sink in the vertical advection term. After the flow levels out the pressure redistribution (return-to-isotropy) term becomes the main sink of streamwisevelocity variance and feeds energy into the vertical velocity component. Therefore, thedevelopment of the vertical velocity variance and shear stress cannot begin until afterdevelopment of an increase in the streamwise velocity variance. Results are comparedwith other experiments, including the flow across shelterbelts, and large-eddy simulations of forest flow.

Forest edge Roughness change Turbulence Wind tunnel 

Copyright information

© Kluwer Academic Publishers 2002

Authors and Affiliations

  • A.P. Morse
    • 1
  • B.A. Gardiner
    • 2
  • B.J. Marshall
    • 3
    • 4
  1. 1.Department of GeographyUniversity of LiverpoolLiverpoolU.K.
  2. 2.Northern Research Station, Forest ResearchForestry CommissionU.K
  3. 3.Wind Engineering Research Group, Department of Engineering ScienceOxford UniversityU.K
  4. 4.MathEngineOxfordU.K

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