Simplified Calculation of the Zero - Plane Displacement 7 from Wind - Speed Profiles

  • Ch . RIOU
  • Published 2001

Abstract

Riou, Ch., 1984. Simplified calculation of the zero-plane displacement from wind-speed profiles. J. Hydrol., 69: 351-357. A simplified method is proposed to calculate zero-plane displacement from windspeed profiles. This method is applied to a wheat crop; accuracy is discussed and the effects of instability are incorporated to improve the result. INTRODUCTION Under neutral atmospheric conditions, the wind-speed profile above vegetation can be described by: U = (U*/h)ln [ ( z d ) / z o ] ( la) U, U1 = (U*/h) In [(z, -d)/(zl 4 1 (1b) 5 , If U is measured at two different heights, this becomes: '$:;;.,,$,@;. :-.. : . , ~ . ~ . ~ . ~ : ~ ~ ~ ~ . : , ~ . ~ : ~ ~ ~ , ~ ~ ~ ~ ; ~ ~ ~ ~ > ,. . . .,,., In these expressions, U is wind velocity; z height of measurement above the soil surface; U, the friction velocity; zo roughness height; h von Karman's constant; and d the zero-level displacement caused by the vegetation. Atmospheric instability causes deviations in these profiles. If the instability is slight, the wind-speed profile may be described by the formula given by Dyer and Hicks (1970): U = ( ~ , / ~ ) [ l n { ( ~ d ) / z ~ } + 4 L ~ ( z d ) l (2) where L is Monin-Obukhov's length, which is negative in this case. * Present address: Institut National de la Recherche Agronomique, Station de Bioclimatologie-Télédétection, Route de St.-Cyr, 78000 Versailles, France.

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Cite this paper

@inproceedings{RIOU2001SimplifiedCO, title={Simplified Calculation of the Zero - Plane Displacement 7 from Wind - Speed Profiles}, author={Ch . RIOU}, year={2001} }