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

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 vertical bar R-F vertical bar 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 vertical bar R-F vertical bar 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 vertical bar R-F vertical bar relate to the flux fractions of a decreasing magnitude for sensible heat but of an increasing magnitude for water vapor.