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Boundary-Layer Meteorology

, Volume 103, Issue 3, pp 391–407 | Cite as

Momentum Transfer By A Mountain Meadow Canopy: A Simulation Analysis Based On Massman's (1997) Model

  • Georg Wohlfahrt
  • Alexander Cernusca
Article

Abstract

Using a mountain meadow as a case study it is the objective of the present paper todevelop a simple parameterisation for the within-canopy variation of the phytoelementdrag (Cd) and sheltering (Pm) coefficients required for Massman's model of momentum transfer by vegetation. A constant ratio between Cd and Pm is found to overestimate wind speed in the upper canopy and underestimate it in the lower canopy.Two simple parameterisations of Cd/Pm as a function of the plant area density and the cumulative plant area index are developed, using values optimised by least-squares regression between measured and predicted within-canopy wind speeds. A validation with independently measured data indicates that both parameterisations work reliably for simulating wind speed in the investigated meadow. Model predictions of the normalised zero-plane displacement height and the momentum roughness length fall only partly within the range of values given in literature, which may be explained by the accumulation of plantmatter close to the soil surface specific for the investigated canopies. The seasonal course of the normalised zero-plane displacement height and the momentum roughness length are discussed in terms of the seasonal variation of the amount and density of plant matter.

Canopy structure Drag coefficient Roughness length Sheltering coefficient Wind speed Zero-plane displacement height 

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Copyright information

© Kluwer Academic Publishers 2002

Authors and Affiliations

  • Georg Wohlfahrt
    • 1
  • Alexander Cernusca
    • 2
  1. 1.Institut für BotanikUniversität InnsbruckInnsbruckAustria
  2. 2.Institut für BotanikUniversität InnsbruckInnsbruckAustria

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