Boundary-Layer Meteorology

, Volume 51, Issue 3, pp 255–268 | Cite as

On the determination of zero-plane displacement and roughness length for flow over forest canopies

  • Aloysius Koufang Lo
Article
Accepted:

Abstract

This paper discusses the importance of the aerodynamic characteristics of forest and other similar canopies to modelling of boundary-layer flow and to estimating the diffusivity coefficients of turbulence transfer mechanisms over such canopies.

The hypothesis of Marunich (1971) reported by Tajchman (1981) that the zero-plane displacement, d, equals the upward displacement of the flow trajectory, is critically examined. It is concluded that Marunich's hypothesis is conceptually incorrect and that calculations of d based on Marunich's hypothesis are inherently in error.

This paper presents a method based on the mass conservation principle and uses wind profiles in and above a forest canopy as the sole input for determining d, z0 and u*.

Sensitivities of calculated results to measurements errors of wind profile data are evaluated. It is found that an error of less than 1% in wind in the logarithmic regime above the canopy can introduce up to 100% errors in calculated values of d, z0 and u*. It is also found that the high sensitivity to wind data accuracy, characteristic of the present method, can be used as a guide for the selection of high quality canopy wind data.

Keywords

Mass Conservation Forest Canopy Roughness Length Profile Data Wind Data 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Kluwer Academic Publishers 1990

Authors and Affiliations

  • Aloysius Koufang Lo
    • 1
  1. 1.Air Quality Processes Research DivisionAtmospheric Environment ServiceDownsviewCanada

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