On the turbulent Prandtl number in the stable atmospheric boundary layer

Grachev, A. A.; Andreas, Edgar L.; Fairall, Christopher W.; Guest, Peter; Persson, P. Ola G.

doi:10.1007/978-0-387-74321-9_12

Cited by 25 publications

(43 citation statements)

References 28 publications

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“…According to Ohya (2001), Grachev et al (2007b), Esau and Grachev (2007), Zilitinkevich et al (2007) and Anderson (2009), the Prandtl number increases with Ri in supercritical conditions. However, the detailed analysis of Grachev et al (2007b) implies that such a result is spurious. When one does not employ the outlier rejection discussed in section 4.1, the resulting SHEBA data do indeed show that Pr increases with the increasing values of Ri.…”

Section: Discussionmentioning

confidence: 95%

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Gradient‐based scales and similarity laws in the stable boundary layer

Sorbjan

2010

Quart J Royal Meteoro Soc

105

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Three gradient-based scaling systems for the stably stratified boundary layer are introduced and examined by using data collected during the SHEBA field programme in the Arctic. The resulting similarity functions for fluxes and variances are expressed in an analytical form, which is expected to be essentially unaffected by self-correlation in a very stable regime. The flux Richardson number Rf is found to be proportional to the Richardson number Ri, with the proportionality coefficient varying slightly with stability, from 1.11 to 1.47. The Prandtl number decreases from 0.9 in nearly neutral conditions to 0.7 for larger values of Ri. The negative correlation coefficient between the vertical velocity and temperature, −r wθ , has a local maximum at Ri of about 0.08, and monotonically decreases with larger values of the Richardson number. The turbulent kinetic energy budget indicates that for Ri > 0.7, turbulence must be non-stationary, i.e. decaying or sporadic. Turbulence within the stably stratified boundary layer can be classified by four regimes: 'nearly neutral' (0 < Ri < 0.02), 'weakly stable' (0.02 < Ri < 0.12), 'very stable' (0.12 < Ri < 0.7), and 'extremely stable' (Ri > 0.7).

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Section: Discussionmentioning

confidence: 95%

“…Detailed overviews of the SHEBA programme and its data can be found in the papers of Andreas et al (1999;2003;, Persson et al (2002) and Grachev et al (2005;2007a;2007b;. Thus, herein, only brief information about SHEBA instruments and data will be provided.…”

Section: Datamentioning

confidence: 99%

Gradient‐based scales and similarity laws in the stable boundary layer

Sorbjan

2010

Quart J Royal Meteoro Soc

105

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“…Recent advancements in parameterizing the SBL followed from recognizing that the onset of turbulence is not associated with a unique critical value of the Richardson number [204] and that the Prandtl number is stability-dependent [205]. However, the few existing wave-like drag parameterizations are still far from being fully adequate [194,198,206].…”

Section: The Role Of Gravity Wavesmentioning

confidence: 99%

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

et al. 2018

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Abstract:The exchange of heat, momentum, and mass in the atmosphere over mountainous terrain is controlled by synoptic-scale dynamics, thermally driven mesoscale circulations, and turbulence. This article reviews the key challenges relevant to the understanding of exchange processes in the mountain boundary layer and outlines possible research priorities for the future. The review describes the limitations of the experimental study of turbulent exchange over complex terrain, the impact of slope and valley breezes on the structure of the convective boundary layer, and the role of intermittent mixing and wave-turbulence interaction in the stable boundary layer. The interplay between exchange processes at different spatial scales is discussed in depth, emphasizing the role of elevated and ground-based stable layers in controlling multi-scale interactions in the atmosphere over and near mountains. Implications of the current understanding of exchange processes over mountains towards the improvement of numerical weather prediction and climate models are discussed, considering in particular the representation of surface boundary conditions, the parameterization of sub-grid-scale exchange, and the development of stochastic perturbation schemes.

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“…For example, over flat terrain, Grachev et al (2007) investigated the effects of self-correlation and stability on the apparent behaviour of the turbulent Prandtl number (a parameter that characterizes the importance of turbulent momentum transfer relative to sensible heat transfer). They found that a bulk Richardson number correlation was more appropriate than other formulations, as it reduced self-correlation.…”

Section: Assessment Of Self-correlationmentioning

confidence: 99%

Similarity Scaling Over a Steep Alpine Slope

Nadeau

Pardyjak

Higgins

et al. 2012

Boundary-Layer Meteorol

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In this study, we investigate the validity of similarity scaling over a steep mountain slope (30-41 • ). The results are based on eddy-covariance data collected during the Slope Experiment near La Fouly (SELF-2010); a field campaign conducted in a narrow valley of the Swiss Alps during summer 2010. The turbulent fluxes of heat and momentum are found to vary significantly with height in the first few metres above the inclined surface. These variations exceed by an order of magnitude the well-accepted maximum 10 % required for the applicability of Monin-Obukhov similarity theory in the surface layer. This could be due to a surface layer that is too thin to be detected or to the presence of advective fluxes. It is shown that local scaling can be a useful tool in these cases when surface-layer theory breaks down. Under convective conditions and after removing the effects of self-correlation, the normalized standard deviations of slope-normal wind velocity, temperature and humidity scale relatively well with z/Λ, where z is the measurement height and Λ(z) the local Obukhov length. However, the horizontal velocity fluctuations are not correlated with z/Λ under all stability regimes. The non-dimensional gradients of wind velocity and temperature are also investigated. For those, the local scaling appears inappropriate, particularly at night when shallow drainage flows prevail and lead to negative wind-speed gradients close to the surface.

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On the turbulent Prandtl number in the stable atmospheric boundary layer

Cited by 25 publications

References 28 publications

Gradient‐based scales and similarity laws in the stable boundary layer

Gradient‐based scales and similarity laws in the stable boundary layer

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

Similarity Scaling Over a Steep Alpine Slope

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