Turbulence behaviors underlying the sensible heat and water vapor flux dissimilarity in a stably stratified flow

• Published in: Environmental fluid mechanics (Dordrecht, Netherlands : 2001) Vol. 23; no. 5; pp. 1193 - 1232
• Main Authors: Guo, Xiaofeng, Yang, Wei, Hong, Jinkyu, Wang, Linlin, Gao, Zhiqiu, Zhou, Degang
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.10.2023; Springer Nature B.V
• Subjects: Air parcels; Air temperature; Amplitude; Amplitudes; Analysis; Anisotropy; Aspect ratio; Classical Mechanics; Connecting; Correlation coefficient; Correlation coefficients; Earth and Environmental Science; Earth Sciences; Eddy covariance; Enthalpy; Environmental Physics; Fast Fourier transformations; Fluctuations; Fluxes; Fourier transforms; Glacier measurements; Glaciers; Heat; Hole size; Hydrogeology; Hydrology/Water Resources; Oceanography; Original Article; Quadrants; Resonant frequencies; Resonant frequency; Scalars; Sensible heat; Stratified flow; Temperature fluctuations; Turbulence; Vortices; Water vapor; Water vapor flux; Water vapor transport; Water vapour; Scalar turbulence; Octant analysis technique; Stably stratified boundary layer; Turbulent flux dissimilarity; Sensible heat and water vapor transport
• ISSN: 1567-7419; 1573-1510
• DOI: 10.1007/s10652-023-09940-2

Based on eddy-covariance measurements over a glacier, we investigate the scalar flux dissimilarity between sensible heat and water vapor transport in a stably stratified flow. The scalar flux correlation coefficient R F is used as a measure of variable levels of the flux similarity, which are often elevated due to a rising degree of the kinetic anisotropy of turbulence. Moreover, sensible heat is transported more efficiently than water vapor; and transport efficiencies of these two scalars are separated in terms of their variability with the velocity aspect ratio. Compared with air temperature fluctuations, turbulence characteristics of the water vapor concentration are subject to a more pronounced modification because of distinct magnitudes of R F . An innovative method is employed for connecting quadrant analysis and cospectral analysis, so that the hyperbolic quadrant-hole size can be coupled to the natural frequency underlying the fast Fourier transform. Then, we introduce a hypothetical octant hole whose size is invoked as a metric for the amplitude scale of fluctuating scalar fluxes. The contributions to R F are quantified for a variety of eddy structures that are associated with different ranges of the amplitude scale. Regarding larger-amplitude fluxes due to heated drier air parcels in descending motions, reductions in R F correspond to increasing flux fractions for water vapor, whereas the flux fractions for sensible heat are largely unchanged. Overall, a more substantial portion of the changes in R F can be ascribed to smaller-amplitude fluxes due to cooled moister air parcels and heated drier air parcels being involved, respectively, in ascending and descending motions. Reductions in R F relate to the flux fractions of a decreasing magnitude for sensible heat but of an increasing magnitude for water vapor. Highlights In a stably stratified flow, dissimilar transport of sensible heat and water vapor is associated with anisotropy properties of turbulence. A new approach is developed for a scrutiny of scalar transport, whereby quadrant analysis and cospectral analysis can be interconnected. Extending octant analysis to scalar turbulence identifies eddy structures that exhibit distinct behaviors indicative of the flux dissimilarity. Comparatively small-amplitude fluxes are accountable for a substantial portion of the changes in the overall level of scalar flux correlation.