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External controls on the transition between stable boundary‐layer turbulence regimes
Author(s) -
Acevedo Otávio C.,
Costa Felipe D.,
Maroneze Rafael,
Carvalho Arlindo D.,
Puhales Franciano S.,
Oliveira Pablo E. S.
Publication year - 2021
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.4027
Subject(s) - turbulence , wind speed , boundary layer , roughness length , atmospheric sciences , turbulence kinetic energy , radiative transfer , snow , surface roughness , environmental science , meteorology , wind profile power law , physics , mechanics , thermodynamics , optics
The mean wind speed at which the stable boundary layer (SBL) experiences a turbulence regime transition ( V r ) depends on other flow characteristics, such as its thermal stability. Here, V r variability is examined both at a single site and across sites using three multiple‐level datasets: Santa Maria, Cooperative Atmosphere–Surface Exchange Study–1999 (CASES‐99), and Fluxes over Snow Surfaces (FLOSS II). A method to determine V r is introduced and validated. It is taken as the mean wind speed at which the vertical gradient of the turbulence velocity scale switches sign. Emphasis is given to the control exerted on V r by quantities that are external to the SBL, such as radiation, roughness, and soil properties. In each of the experiments, V r increases with net radiative loss at the surface ( R n ) at a rate that is site‐dependent. It also increases for smaller roughness lengths, as indicated by its wind direction dependence. No conclusive relationship has been found between V r and downward longwave radiation observed at the surface. The across‐site comparison indicates that soil heat capacity influences the rate at which V r increases with R n .