Katabatic Flow Structures Indicative of the Flux Dissimilarity for Stable Stratification

Xiaofeng Guo; Wei Yang; Zhiqiu Gao; Linlin Wang; Jinkyu Hong; Baohong Ding; Long Zhao; Degang Zhou; Kun Yang

doi:10.1007/s10546-021-00660-y

Katabatic Flow Structures Indicative of the Flux Dissimilarity for Stable Stratification

Xiaofeng Guo, Wei Yang, Zhiqiu Gao, Linlin Wang, Jinkyu Hong, Baohong Ding, Long Zhao, Degang Zhou, Kun Yang

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3 Citations (Scopus)

Abstract

Based on observations over an alpine glacier, we investigate the turbulent flux dissimilarity between momentum and sensible heat transfer in a stably stratified katabatic flow. The flux correlation coefficient R_F is employed as a measure of variable levels of the flux similarity, which are found to be modulated by the anisotropy of turbulence. In the katabatic wind regime over this glacier, heat is transported more efficiently than momentum. Based on quadrant analysis, the sweep–ejection differences in the flux fraction constitute turbulence characteristics in terms of the velocity aspect ratio, which unravel dissimilar transport of momentum and heat. Moreover, an innovative method is established for connecting quadrant analysis and cospectral analysis, whereby the hyperbolic quadrant hole size is coupled to the frequency underlying the fast Fourier transform. In extending applications of octant analysis, we introduce a hypothetical octant hole, whose size is solicited as a proxy for the amplitude scale of fluctuating fluxes. The contributions to R_F can then be quantified for eddy structures that are associated with different amplitude scales. The katabatic flow structures identified from octant analysis differ in their behaviour so helping illuminate the outcome of flux dissimilarity. Exhibited as a statistical behaviour regardless of amplitude scale, along-wind rapid motions of heated air parcels can modify fractional contributions to the heat flux instead of the momentum flux, with reductions in R_F related to decreasing heat-flux fractions. Besides, along-wind slow motions of cooled air parcels cannot modify the flux fractions for both momentum and heat. Thus, the flux dissimilarity due to low-speed low-temperature eddies cannot be explicable in terms of the flux fractions alone. These findings are an incipient step towards physical understanding of the turbulent flux dissimilarity for a stably stratified katabatic flow.

Original language	English
Pages (from-to)	379-415
Number of pages	37
Journal	Boundary-Layer Meteorology
Volume	182
Issue number	3
DOIs	https://doi.org/10.1007/s10546-021-00660-y
Publication status	Published - 2022 Mar

Bibliographical note

Funding Information:
XG, ZG and LW are funded by the Second Tibetan Plateau Scientific Expedition and Research Program (Grant 2019QZKK0102); JH is funded by the National Research Foundation of Korea that is sponsored by the South Korean government (MSIT) (Grant NRF-2018R1A5A1024958). The software for wavelet analysis is available at http://atoc.colorado.edu/research/wavelets (University of Colorado Boulder) courtesy of Christopher Torrence and Gilbert P. Compo. Supporting data for the authors’ primary findings are publicly available at http://doi.org/10.6084/m9.figshare.14906526 .

Funding Information:
XG, ZG and LW are funded by the Second Tibetan Plateau Scientific Expedition and Research Program (Grant 2019QZKK0102); JH is funded by the National Research Foundation of Korea that is sponsored by the South Korean government (MSIT) (Grant NRF-2018R1A5A1024958). The software for wavelet analysis is available at http://atoc.colorado.edu/research/wavelets (University of Colorado Boulder) courtesy of Christopher Torrence and Gilbert P. Compo. Supporting data for the authors? primary findings are publicly available at http://doi.org/10.6084/m9.figshare.14906526.

Publisher Copyright:
© 2021, The Author(s), under exclusive licence to Springer Nature B.V.

All Science Journal Classification (ASJC) codes

Atmospheric Science

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10.1007/s10546-021-00660-y

Cite this

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title = "Katabatic Flow Structures Indicative of the Flux Dissimilarity for Stable Stratification",

abstract = "Based on observations over an alpine glacier, we investigate the turbulent flux dissimilarity between momentum and sensible heat transfer in a stably stratified katabatic flow. The flux correlation coefficient RF is employed as a measure of variable levels of the flux similarity, which are found to be modulated by the anisotropy of turbulence. In the katabatic wind regime over this glacier, heat is transported more efficiently than momentum. Based on quadrant analysis, the sweep–ejection differences in the flux fraction constitute turbulence characteristics in terms of the velocity aspect ratio, which unravel dissimilar transport of momentum and heat. Moreover, an innovative method is established for connecting quadrant analysis and cospectral analysis, whereby the hyperbolic quadrant hole size is coupled to the frequency underlying the fast Fourier transform. In extending applications of octant analysis, we introduce a hypothetical octant hole, whose size is solicited as a proxy for the amplitude scale of fluctuating fluxes. The contributions to RF can then be quantified for eddy structures that are associated with different amplitude scales. The katabatic flow structures identified from octant analysis differ in their behaviour so helping illuminate the outcome of flux dissimilarity. Exhibited as a statistical behaviour regardless of amplitude scale, along-wind rapid motions of heated air parcels can modify fractional contributions to the heat flux instead of the momentum flux, with reductions in RF related to decreasing heat-flux fractions. Besides, along-wind slow motions of cooled air parcels cannot modify the flux fractions for both momentum and heat. Thus, the flux dissimilarity due to low-speed low-temperature eddies cannot be explicable in terms of the flux fractions alone. These findings are an incipient step towards physical understanding of the turbulent flux dissimilarity for a stably stratified katabatic flow.",

author = "Xiaofeng Guo and Wei Yang and Zhiqiu Gao and Linlin Wang and Jinkyu Hong and Baohong Ding and Long Zhao and Degang Zhou and Kun Yang",

note = "Funding Information: XG, ZG and LW are funded by the Second Tibetan Plateau Scientific Expedition and Research Program (Grant 2019QZKK0102); JH is funded by the National Research Foundation of Korea that is sponsored by the South Korean government (MSIT) (Grant NRF-2018R1A5A1024958). The software for wavelet analysis is available at http://atoc.colorado.edu/research/wavelets (University of Colorado Boulder) courtesy of Christopher Torrence and Gilbert P. Compo. Supporting data for the authors{\textquoteright} primary findings are publicly available at http://doi.org/10.6084/m9.figshare.14906526 . Funding Information: XG, ZG and LW are funded by the Second Tibetan Plateau Scientific Expedition and Research Program (Grant 2019QZKK0102); JH is funded by the National Research Foundation of Korea that is sponsored by the South Korean government (MSIT) (Grant NRF-2018R1A5A1024958). The software for wavelet analysis is available at http://atoc.colorado.edu/research/wavelets (University of Colorado Boulder) courtesy of Christopher Torrence and Gilbert P. Compo. Supporting data for the authors? primary findings are publicly available at http://doi.org/10.6084/m9.figshare.14906526. Publisher Copyright: {\textcopyright} 2021, The Author(s), under exclusive licence to Springer Nature B.V.",

year = "2022",

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doi = "10.1007/s10546-021-00660-y",

language = "English",

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AU - Guo, Xiaofeng

AU - Yang, Wei

AU - Gao, Zhiqiu

AU - Wang, Linlin

AU - Hong, Jinkyu

AU - Ding, Baohong

AU - Zhao, Long

AU - Zhou, Degang

AU - Yang, Kun

N1 - Funding Information: XG, ZG and LW are funded by the Second Tibetan Plateau Scientific Expedition and Research Program (Grant 2019QZKK0102); JH is funded by the National Research Foundation of Korea that is sponsored by the South Korean government (MSIT) (Grant NRF-2018R1A5A1024958). The software for wavelet analysis is available at http://atoc.colorado.edu/research/wavelets (University of Colorado Boulder) courtesy of Christopher Torrence and Gilbert P. Compo. Supporting data for the authors’ primary findings are publicly available at http://doi.org/10.6084/m9.figshare.14906526 . Funding Information: XG, ZG and LW are funded by the Second Tibetan Plateau Scientific Expedition and Research Program (Grant 2019QZKK0102); JH is funded by the National Research Foundation of Korea that is sponsored by the South Korean government (MSIT) (Grant NRF-2018R1A5A1024958). The software for wavelet analysis is available at http://atoc.colorado.edu/research/wavelets (University of Colorado Boulder) courtesy of Christopher Torrence and Gilbert P. Compo. Supporting data for the authors? primary findings are publicly available at http://doi.org/10.6084/m9.figshare.14906526. Publisher Copyright: © 2021, The Author(s), under exclusive licence to Springer Nature B.V.

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N2 - Based on observations over an alpine glacier, we investigate the turbulent flux dissimilarity between momentum and sensible heat transfer in a stably stratified katabatic flow. The flux correlation coefficient RF is employed as a measure of variable levels of the flux similarity, which are found to be modulated by the anisotropy of turbulence. In the katabatic wind regime over this glacier, heat is transported more efficiently than momentum. Based on quadrant analysis, the sweep–ejection differences in the flux fraction constitute turbulence characteristics in terms of the velocity aspect ratio, which unravel dissimilar transport of momentum and heat. Moreover, an innovative method is established for connecting quadrant analysis and cospectral analysis, whereby the hyperbolic quadrant hole size is coupled to the frequency underlying the fast Fourier transform. In extending applications of octant analysis, we introduce a hypothetical octant hole, whose size is solicited as a proxy for the amplitude scale of fluctuating fluxes. The contributions to RF can then be quantified for eddy structures that are associated with different amplitude scales. The katabatic flow structures identified from octant analysis differ in their behaviour so helping illuminate the outcome of flux dissimilarity. Exhibited as a statistical behaviour regardless of amplitude scale, along-wind rapid motions of heated air parcels can modify fractional contributions to the heat flux instead of the momentum flux, with reductions in RF related to decreasing heat-flux fractions. Besides, along-wind slow motions of cooled air parcels cannot modify the flux fractions for both momentum and heat. Thus, the flux dissimilarity due to low-speed low-temperature eddies cannot be explicable in terms of the flux fractions alone. These findings are an incipient step towards physical understanding of the turbulent flux dissimilarity for a stably stratified katabatic flow.

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Katabatic Flow Structures Indicative of the Flux Dissimilarity for Stable Stratification

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