Simplification and Validation of a Spectral-Tensor Model for Turbulence Including Atmospheric Stability

Abhijit Chougule*, Jakob Mann, Mark C. Kelly, Gunner Chr. Larsen

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

A spectral-tensor model of non-neutral, atmospheric-boundary-layer turbulence is evaluated using Eulerian statistics from single-point measurements of the wind speed and temperature at heights up to 100 m, assuming constant vertical gradients of mean wind speed and temperature. The model has been previously described in terms of the dissipation rate epsilon, the length scale of energy-containing eddies L, a turbulence anisotropy parameter Gamma, the Richardson number Ri, and the normalized rate of destruction of temperature variance eta(theta) equivalent to epsilon(theta)/epsilon. Here, the latter two parameters are collapsed into a single atmospheric stability parameter z/L usingMonin-Obukhov similarity theory, where z is the height above the Earth's surface, and L is the Obukhov length corresponding to {Ri ,eta(theta)}. Model outputs of the one-dimensional velocity spectra, as well as cospectra of the streamwise and/or vertical velocity components, and/or temperature, and cross-spectra for the spatial separation of all three velocity components and temperature, are compared with measurements. As a function of the four model parameters, spectra and cospectra are reproduced quite well, but horizontal temperature fluxes are slightly underestimated in stable conditions. In moderately unstable stratification, our model reproduces spectra only up to a scale similar to 1 km. The model also overestimates coherences for vertical separations, but is less severe in unstable than in stable cases.
Original languageEnglish
JournalBoundary-Layer Meteorology
Volume167
Issue number3
Pages (from-to)371-397
Number of pages27
ISSN0006-8314
DOIs
Publication statusPublished - 2018

Keywords

  • Atmospheric stability
  • Atmospheric turbulence
  • Boundary layer
  • Spectra
  • Spectral tensor

Cite this

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title = "Simplification and Validation of a Spectral-Tensor Model for Turbulence Including Atmospheric Stability",
abstract = "A spectral-tensor model of non-neutral, atmospheric-boundary-layer turbulence is evaluated using Eulerian statistics from single-point measurements of the wind speed and temperature at heights up to 100 m, assuming constant vertical gradients of mean wind speed and temperature. The model has been previously described in terms of the dissipation rate epsilon, the length scale of energy-containing eddies L, a turbulence anisotropy parameter Gamma, the Richardson number Ri, and the normalized rate of destruction of temperature variance eta(theta) equivalent to epsilon(theta)/epsilon. Here, the latter two parameters are collapsed into a single atmospheric stability parameter z/L usingMonin-Obukhov similarity theory, where z is the height above the Earth's surface, and L is the Obukhov length corresponding to {Ri ,eta(theta)}. Model outputs of the one-dimensional velocity spectra, as well as cospectra of the streamwise and/or vertical velocity components, and/or temperature, and cross-spectra for the spatial separation of all three velocity components and temperature, are compared with measurements. As a function of the four model parameters, spectra and cospectra are reproduced quite well, but horizontal temperature fluxes are slightly underestimated in stable conditions. In moderately unstable stratification, our model reproduces spectra only up to a scale similar to 1 km. The model also overestimates coherences for vertical separations, but is less severe in unstable than in stable cases.",
keywords = "Atmospheric stability, Atmospheric turbulence, Boundary layer, Spectra, Spectral tensor",
author = "Abhijit Chougule and Jakob Mann and Kelly, {Mark C.} and Larsen, {Gunner Chr.}",
year = "2018",
doi = "10.1007/s10546-018-0332-z",
language = "English",
volume = "167",
pages = "371--397",
journal = "Boundary-Layer Meteorology",
issn = "0006-8314",
publisher = "Springer Netherlands",
number = "3",

}

Simplification and Validation of a Spectral-Tensor Model for Turbulence Including Atmospheric Stability. / Chougule, Abhijit; Mann, Jakob; Kelly, Mark C.; Larsen, Gunner Chr.

In: Boundary-Layer Meteorology, Vol. 167, No. 3, 2018, p. 371-397.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Simplification and Validation of a Spectral-Tensor Model for Turbulence Including Atmospheric Stability

AU - Chougule, Abhijit

AU - Mann, Jakob

AU - Kelly, Mark C.

AU - Larsen, Gunner Chr.

PY - 2018

Y1 - 2018

N2 - A spectral-tensor model of non-neutral, atmospheric-boundary-layer turbulence is evaluated using Eulerian statistics from single-point measurements of the wind speed and temperature at heights up to 100 m, assuming constant vertical gradients of mean wind speed and temperature. The model has been previously described in terms of the dissipation rate epsilon, the length scale of energy-containing eddies L, a turbulence anisotropy parameter Gamma, the Richardson number Ri, and the normalized rate of destruction of temperature variance eta(theta) equivalent to epsilon(theta)/epsilon. Here, the latter two parameters are collapsed into a single atmospheric stability parameter z/L usingMonin-Obukhov similarity theory, where z is the height above the Earth's surface, and L is the Obukhov length corresponding to {Ri ,eta(theta)}. Model outputs of the one-dimensional velocity spectra, as well as cospectra of the streamwise and/or vertical velocity components, and/or temperature, and cross-spectra for the spatial separation of all three velocity components and temperature, are compared with measurements. As a function of the four model parameters, spectra and cospectra are reproduced quite well, but horizontal temperature fluxes are slightly underestimated in stable conditions. In moderately unstable stratification, our model reproduces spectra only up to a scale similar to 1 km. The model also overestimates coherences for vertical separations, but is less severe in unstable than in stable cases.

AB - A spectral-tensor model of non-neutral, atmospheric-boundary-layer turbulence is evaluated using Eulerian statistics from single-point measurements of the wind speed and temperature at heights up to 100 m, assuming constant vertical gradients of mean wind speed and temperature. The model has been previously described in terms of the dissipation rate epsilon, the length scale of energy-containing eddies L, a turbulence anisotropy parameter Gamma, the Richardson number Ri, and the normalized rate of destruction of temperature variance eta(theta) equivalent to epsilon(theta)/epsilon. Here, the latter two parameters are collapsed into a single atmospheric stability parameter z/L usingMonin-Obukhov similarity theory, where z is the height above the Earth's surface, and L is the Obukhov length corresponding to {Ri ,eta(theta)}. Model outputs of the one-dimensional velocity spectra, as well as cospectra of the streamwise and/or vertical velocity components, and/or temperature, and cross-spectra for the spatial separation of all three velocity components and temperature, are compared with measurements. As a function of the four model parameters, spectra and cospectra are reproduced quite well, but horizontal temperature fluxes are slightly underestimated in stable conditions. In moderately unstable stratification, our model reproduces spectra only up to a scale similar to 1 km. The model also overestimates coherences for vertical separations, but is less severe in unstable than in stable cases.

KW - Atmospheric stability

KW - Atmospheric turbulence

KW - Boundary layer

KW - Spectra

KW - Spectral tensor

U2 - 10.1007/s10546-018-0332-z

DO - 10.1007/s10546-018-0332-z

M3 - Journal article

VL - 167

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JO - Boundary-Layer Meteorology

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SN - 0006-8314

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