TY - JOUR

T1 - Modelling Velocity Spectra in the Lower Part of the Planetary Boundary Layer

AU - Olesen, H.R.

AU - Larsen, Søren Ejling

AU - Højstrup, Jørgen

PY - 1984

Y1 - 1984

N2 - Principles used when constructing models for velocity spectra are reviewed. Based upon data from
the Kansas and Minnesota experiments, simple spectral models are set up for all velocity components in
stable air at low heights, and for the vertical spectrum in unstable air through a larger part of the planetary
boundary layer. Knowledge of the variation with stability of the (reduced) frequency f, for the spectral
maximum is utilized in this modelling. Stable spectra may be normalized so that they adhere to one curve
only, irrespective of stability, and unstable w-spectra may also be normalized to fit one curve.
The problem of using filtered velocity variances when modelling spectra is discussed. A simplified
procedure to provide a first estimate of the filter effect is given.
In stable, horizontal velocity spectra, there is often a ‘gap’ at low frequencies. Using dimensional
considerations and the spectral model previously derived, an expression for the gap frequency is found.

AB - Principles used when constructing models for velocity spectra are reviewed. Based upon data from
the Kansas and Minnesota experiments, simple spectral models are set up for all velocity components in
stable air at low heights, and for the vertical spectrum in unstable air through a larger part of the planetary
boundary layer. Knowledge of the variation with stability of the (reduced) frequency f, for the spectral
maximum is utilized in this modelling. Stable spectra may be normalized so that they adhere to one curve
only, irrespective of stability, and unstable w-spectra may also be normalized to fit one curve.
The problem of using filtered velocity variances when modelling spectra is discussed. A simplified
procedure to provide a first estimate of the filter effect is given.
In stable, horizontal velocity spectra, there is often a ‘gap’ at low frequencies. Using dimensional
considerations and the spectral model previously derived, an expression for the gap frequency is found.

U2 - 10.1007/BF00119794

DO - 10.1007/BF00119794

M3 - Journal article

VL - 29

SP - 285

EP - 312

JO - Boundary-Layer Meteorology

JF - Boundary-Layer Meteorology

SN - 0006-8314

IS - 3

ER -