The Effect of Stratification on the Aerodynamic Roughness Length and Displacement Height |
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| Authors: | S S Zilitinkevich I Mammarella A A Baklanov S M Joffre |
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| Institution: | (1) Division of Atmospheric Sciences, University of Helsinki, Box 64, 00014 Helsinki, Finland;(2) Department of Meterological Research, Finnish Meteorological Institute, Box 503, 00101 Helsinki, Finland;(3) Nansen Environmental and Remote Sensing Centre, Thormohlensgt. 47, 5006 Bergen, Norway;(4) Danish Meteorological Institute, Lyngbyvej 100, 2100 Copenhagen, Denmark |
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| Abstract: | The roughness length, z
0u
, and displacement height, d
0u
, characterise the resistance exerted by the roughness elements on turbulent flows and provide a conventional boundary condition
for a wide range of turbulent-flow problems. Classical laboratory experiments and theories treat z
0u
and d
0u
as geometric parameters independent of the characteristics of the flow. In this paper, we demonstrate essential stability
dependences—stronger for the roughness length (especially in stable stratification) and weaker but still pronounced for the
displacement height. We develop a scaling-analysis model for these dependences and verify it against experimental data. |
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| Keywords: | Air pollution Convection Displacement height Logarithmic surface layer Roughness length Stable stratification Urban and vegetation canopies |
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