Mean scalar concentration profile in a sheared and thermally stratified atmospheric surface layer

Abstract

Using only dimensional considerations, Monin and Obukhov proposed a 'universal' stability correction function φc(ζ) that accounts for distortions caused by thermal stratification to the mean scalar concentration profile in the atmospheric surface layer when the flow is stationary, planar homogeneous, fully turbulent, and lacking any subsidence. For nearly six decades, their analysis provided the basic framework for almost all operational models and data interpretation in the lower atmosphere. However, the canonical shape of φc(ζ) and the departure from the Reynold's analogy continue to defy theoretical explanation. Here, the basic processes governing the scalar-velocity cospectrum, including buoyancy and the scaling laws describing the velocity and temperature spectra, are considered via a simplified co-spectral budget. The solution to this co-spectral budget is then used to derive φc(ζ), thereby establishing a link between the energetics of turbulent velocity and scalar concentration fluctuations and the bulk flow describing the mean scalar concentration profile. The resulting theory explains all the canonical features of φc(ζ), including the onset of power-laws for various stability regimes and their concomitant exponents, as well as the causes of departure from Reynold's analogy.

Surface-Layer Similarity Functions for Dissipation Rate and Structure Parameters of Temperature and Humidity Based on Eleven Field Experiments

“…This flux-profile relation showed a better agreement with the corresponding f C T 2 functions. More recently, Katul et al (2011Katul et al ( , 2013) proposed flux-profile relations that account for anisotropy, advection and pressure fluctuations, which could in the same way give better correspondence with the MOST relations shown here. Figure 2 has the same set-up as Fig.…”

“…Also for f C q 2 under stable conditions the flux-profile-derived function deviates from the function found herein. This difference may again be related to the fact that intermittent turbulence (Beljaars and Holtslag 1991), or anisotropy, advection and pressure fluctuations (Katul et al 2011(Katul et al , 2013 are missing mechanisms in the flux-profile relations as we described in Sect. 4.1.…”

Influence of drought on growing season carbon and water cycling with changing land cover

“…There was a significant difference (p<0.01) in mean S 0 between sites every year, with sweeps more prominent in momentum transport at KON and ejecting motions from the canopy tending to be more dominant at K4B. Some studies have shown that S 0 is higher with denser canopies (Katul et al, 2006(Katul et al, , 2013, which would lead to an expectation of increasing S 0 seasonally and higher S 0 values at K4B, where LAI tends to be higher. However, results for momentum show the opposite, with S 0 steadily lower at K4B and tending to decrease slightly over the growing season, corresponding to increased ejections from the canopy with greater canopy density.…”

“…In the surface layer, the dominant motion depends on stability and canopy conditions. Under neutral conditions, sweeps and ejections are typically balanced, while under unstable conditions ejections dominate over sparse canopies and sweeps dominate over denser canopies (Katul et al, 2006(Katul et al, , 2013. It is hypothesized that the ratio of sweeps and ejections will differ between a stable grassland and one experiencing significant woody encroachment with sweeps becoming more prominent with the resultant changes in canopy composition.…”

Scalar Flux–Gradient Relationships Under Unstable Conditions over Water in Coastal Regions

“…While these flux-gradient relationships are assumed to be universal, the exact functional forms of these relationships cannot be predicted by MOST (Stull 1988;Foken 2008). There have been new studies exploring the functional forms of these flux-gradient relationships from a theoretical perspective (Katul et al 2011(Katul et al , 2013Li et al 2012b), which still rely significantly on experimental observations. The functional forms of these flux-gradient relationships have been the topic of many field campaigns, including the famous Kansas experiment (Dyer and Hicks 1970;Businger et al 1971) over land and the Coupled Ocean-Atmosphere Response Experiment (COARE) (Fairall et al 1996(Fairall et al , 2003 over ocean.…”