Impact of Nocturnal Low-Level Jets on Near-Surface Turbulence Kinetic Energy

Duarte, Henrique F.; Leclerc, Monique Y.; Zhang, Gengsheng; Durden, David; Kurzeja, Robert J.; Parker, Matthew; Werth, David

doi:10.1007/s10546-015-0030-z

Cited by 13 publications

(20 citation statements)

References 57 publications

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“…As night 2 progresses, however, the turbulent activity actually increases as the jet forms (Fig. 15b), as buoyant damping and dissipation are balanced by shear production, also seen in observed TKE budgets (Duarte et al 2015). This is in agreement with Fig.…”

Section: Resultssupporting

confidence: 88%

Quantifying the local influence at a tall tower site in nocturnal conditions

Werth

Buckley

Zhang

et al. 2015

Theor Appl Climatol

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The influence of the local terrestrial environment on nocturnal atmospheric CO 2 measurements at a 329-m television transmitter tower (and a component of a CO 2 monitoring network) was estimated with a tracer release experiment and a subsequent simulation of the releases. This was done to characterize the vertical transport of emissions from the surface to the uppermost tower level and how it is affected by atmospheric stability. The tracer release experiment was conducted over two nights in May of 2009 near the Department of Energy's Savannah River Site (SRS) in South Carolina. Tracer was released on two contrasting nights-slightly stable and moderately stable-from several upwind surface locations. Measurements at the 329-m level on both nights indicate that tracer was able to mix vertically within a relatively short (∼24 km) distance, implying that nocturnal stable conditions do not necessarily prevent vertical dispersion in the boundary layer and that CO 2 measurements at the tower are at least partly influenced by nearby emissions. A simulation of the tracer release is used to calculate the tower footprint on the two nights to estimate the degree to which the local domain affects the tower readings. The effect of the nocturnal boundary layer on the area sampled by the tower can be seen clearly, as the footprints were affected by changes in stability. The contribution of local sources to the measurements at the tower was minimal, however, suggesting that nocturnal concentrations at upper levels are contributed mostly by regional sources.

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Section: Resultssupporting

confidence: 88%

Quantifying the local influence at a tall tower site in nocturnal conditions

Werth

Buckley

Zhang

et al. 2015

Theor Appl Climatol

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“…However, in recent decades this assumption was challenged by many experimental studies which presented evidence of local imbalance (e.g. Högström, ; Frenzen and Vogel, ; Li et al ; Duarte et al ). The observed imbalance, showing excess or inadequate TKE dissipation under neutral conditions, underlines the importance of the transport (and possibly advection) terms to either the gain or loss of TKE, respectively.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…Indeed, determining stability functions of the TKE budget terms has been one of the objectives in the field of boundary layer turbulence over the past forty years (e.g. Businger et al ; Wyngaard and Coté, ; Högström, ; Oncley et al ; Frenzen and Vogel, ; Li et al ; Duarte et al ). Since the milestone 1968 Kansas experiment, many field campaigns have been conducted, which have enabled deeper understanding of the behaviour of different terms in the TKE budget.…”

Section: Introductionmentioning

confidence: 99%

“…However, recent studies have challenged this assumption for all stabilities, showing that TKE may be locally imbalanced and that transport terms are important (e.g. Högström, ; Oncley et al ; Frenzen and Vogel, ; Pahlow et al ; Li et al ; Duarte et al ). These studies have found either excess or inadequate TKE dissipation, suggesting TKE gain or loss via transport terms, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…This problem is especially pronounced in the stable boundary layer (SBL), where turbulence is influenced by many other factors such as low‐level jets (LLJs), gravity waves, density currents or Kelvin–Helmholtz shear instability (Cheng et al ), or over sloping terrain where katabatic flows develop, with along‐slope heat flux having an important role in the buoyant production and destruction of TKE (Grachev et al ; Oldroyd et al ). The analysis of TKE budget terms under the effect of LLJs has shown that the pressure transport term plays an important role close to the surface, but a consensus on whether the pressure transport is a source or sink term is still missing (Duarte et al , and references therein). A considerable amount of research has been devoted to TKE budget studies in the SL over homogeneous surfaces, but little research has focused on budgets above heterogeneous and rough surfaces.…”

Section: Introductionmentioning

confidence: 99%

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Turbulence kinetic energy budget in the stable boundary layer over a heterogeneous surface

Babić

Rotach

2018

Quart J Royal Meteoro Soc

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This study presents turbulence kinetic energy (TKE) budget terms above tall, deciduous walnut canopy in the wintertime stable boundary layer (SBL) and makes a comparison to well‐known results of horizontally homogeneous and flat (HHF) terrain. Turbulence measurements performed at five levels above the canopy height (approximately h=18 m) enable the investigation of joint effect of the roughness sublayer (RSL) and the transition layer on the TKE budget terms. Each term of the TKE budget is investigated within the framework of local similarity theory. Kolomogorov's similarity hypothesis assumes local isotropy within the inertial subrange. Thoroughly testing the local isotropy hypothesis for the present dataset results in a ratio of the horizontal spectral densities (Sv/Su) approaching 4/3, while the ratio of the vertical to the longitudinal spectral density (Sw/Su) is less than the canonical value of 4/3 (even less than 1) for all levels indicating anisotropic turbulence even at very small scales above the canopy. As a consequence, estimated values of TKE dissipation rate (ε) from the vertical component are smaller than those obtained from the horizontal velocity components. This finding has a direct influence on the applicability of classical Kansas spectral models valid for HHF terrain as well as on the budget of wind variances. Additionally, the behavior of the non‐dimensional gradient of mean wind speed is tested with regard to conformity to z‐less scaling requirements (i.e. linear dependence on stability). It is confirmed that a stability threshold (such as Rf > 0.25, where Rf is the flux Richardson number) is a stronger determinant of z‐less behavior than the existence of a well‐defined inertial subrange ‐ opposite to observations in the SBL over ideal flat surfaces. Finally, the local equilibrium between the production and destruction of TKE within the RSL and transition layer is analyzed.

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Specifics of the Near-Surface Turbulence

Foken,

Mauder

2024

Micrometeorology

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Impact of Nocturnal Low-Level Jets on Near-Surface Turbulence Kinetic Energy

Cited by 13 publications

References 57 publications

Quantifying the local influence at a tall tower site in nocturnal conditions

Quantifying the local influence at a tall tower site in nocturnal conditions

Turbulence kinetic energy budget in the stable boundary layer over a heterogeneous surface

Specifics of the Near-Surface Turbulence

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