Premium
Surface‐layer description under free‐convection conditions
Author(s) -
Sykes R. I.,
Henn D. S.,
Lewellen W. S.
Publication year - 1993
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49711951103
Subject(s) - eddy , mechanics , surface roughness , boundary layer , convection , surface finish , materials science , convective boundary layer , roughness length , turbulence , scaling , surface layer , magnitude (astronomy) , layer (electronics) , optics , planetary boundary layer , physics , meteorology , geometry , composite material , mathematics , wind profile power law , wind speed , astronomy
Large‐eddy simulation is used to study the structure of the boundary layer close to the surface under free‐convection conditions. The magnitude of the surface friction velocity induced by the large convective eddies is determined as a function of the convective velocity scale, w * , and the surface, roughness length, z 0 . A simple analytic scaling form is obtained from a balance of forces in the wall layer induced by the convective eddies, giving the effective thickness of the layer and the effective surface stress and temperature dependence. The depth of the wall layer varies significantly with surface roughness and is extremely thin for small roughness, e.g. 0.5% of the mixed layer depth for a roughness length of 10 −4 z i . The analytic forms are consistent with the numerical predictions over the range of roughness length considered. The probability distribution of the instantaneous surface friction velocity (magnitude only) is examined and found to be reasonably close to Gaussian.