Physical Model of Diurnal Heating in the Vicinity of a Two-Dimensional Ridge

Chen, Ruirong; Berman, Neil S.; Boyer, Don L.; Fernando, Harindra J. S.

doi:10.1175/1520-0469(1996)053<0062:pmodhi>2.0.co;2

Cited by 19 publications

(26 citation statements)

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“…They developed linear and nonlinear models and, in the former, flow past a heated low hill could be analysed by superposing the separate responses of thermal and orographic forcing. To our knowledge, no laboratory experiments delving into flow separation in heated mountainous terrain have been reported hitherto, although a number of studies have dealt with flow over a heated uniform slope (Chen et al 1996) and complex topography with spatially varying slopes (Berman et al 1995;Reuten et al 2007) in the presence of background stable stratification. The stable stratification appears to have a tendency to suppress flow separation, and this case is relevant to the morning transition in complex terrain during which the nocturnal inversion is destroyed by heating of the ground during sunrise (Lu & Turco 1994;Princevac & Fernando 2008).…”

Section: Previous Related Workmentioning

confidence: 99%

Separation of upslope flow over a uniform slope

2015

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Motivated by the importance of understanding mountain weather during periods of thermal convection, a laboratory study was conducted to investigate the separation of an upslope (anabatic) flow on a two-dimensional heated mountainous slope in the absence of a background mean flow. Three flow regimes were identified. In the first, at slope angles β larger than a critical value β c ≈ 20 • , the separated flow generated a rising plume completely fed by the anterior upslope flow. For this case, a simple model based on a balance between the opposing vorticities of baroclinicity and shear was proposed to predict the location of the separation point relative to the mountain base. The model also predicts the velocity and length scales at separation as well as those of the rising plume after separation. In the second regime, 10 • < β β c , the volume flow of the separated plume was not fully supplied by the upslope flow, requiring entrainment of additional ambient fluid at the base of the plume source. The third regime occurred when β 10 • , wherein the plume almost completely engulfed the slope, similar to a buoyant plume emanating from a source of finite dimensions, thus overshadowing the upslope flow. Measurements of the separation point conducted during the MATERHORN field research program were consistent with the results of the laboratory experiments and modelling.

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Section: Previous Related Workmentioning

confidence: 99%

Separation of upslope flow over a uniform slope

2015

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“…Turbulence within the CBL over a plain and thermal advection by slope winds actually modulate each other (Chen et al 1996). Turbulence within the CBL over a plain and thermal advection by slope winds actually modulate each other (Chen et al 1996).…”

Section: Interaction Between Upslope Flows and The Cblmentioning

confidence: 99%

Structure of the Atmospheric Boundary Layer in the Vicinity of a Developing Upslope Flow System: A Numerical Model Study

Serafin

Zardi

2010

Journal of the Atmospheric Sciences

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The development of a morning upslope flow is studied by means of idealized numerical simulations. In particular, two cases are examined: a plane slope connecting a lower plain and an elevated plateau and a symmetric mountain in the middle of a uniform plain. The analysis examines various steepness cases and aims at understanding the processes occurring in the area of transition between the upslope flow region and the convective boundary layers (CBLs) growing nearby. A characteristic sequence of events is recognized in the simulations, and their relationship with the along-slope variability of the thermal energy and turbulent kinetic energy budgets is studied. Features occurring after the onset of the upslope wind include a transient depression in the boundary layer depth at the base of the slope and the formation of elevated turbulent layers above the CBL, caused by the divergence of turbulent flow from a thermal plume at the slope top. Numerical evidence agrees well with the results of previous experiments, including both field campaigns and water tank models. It is observed that the occurrence of streamwise inhomogeneities in the upslope flow field favors the occurrence of a multilayered vertical structure of the CBL near heated slopes. Multiple layering appears to be a transient feature, only persisting until sufficient heating causes the merging of the CBL with the overlying elevated turbulent layers. The analysis suggests that the slope steepness is an important factor in determining the speed at which the boundary layer structure near a slope evolves in time: in particular, the development of the wind system appears to occur faster in the vicinity of a steeper slope.

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“…The lower coefficient in the Regime III equilibrium is supported by Darby et al (2002) who found that upslope flows alone have lower speeds than upslope flows combined with sea breezes. The mechanism whereby growth of the upslope-flow circulation characterizes Regime II, and leads to a lower balance in Regime III, can be approached by considering the results of Chen et al (1996), who discovered that the speed of upslope flows is larger at a given slope angle when ambient stability is stronger. According to this result, the growth of the upslope-flow circulation and its link to Regime II is then more significant at a given slope angle when ambient stability becomes stronger, which explains the dependence on stability detected in Regime II.…”

Section: The Nature Of the Equilibrium In Regime IIImentioning

confidence: 99%

Sea-breeze scaling from numerical model simulations, part II: Interaction between the sea breeze and slope flows

Porson

Steyn

Schayes

2006

Boundary-Layer Meteorol

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Numerical model simulations of sea-breeze circulations in the presence of idealized topography are subjected to dimensional analysis in order to capture the dynamics of the sea-breeze circulation combined with an upslope-flow circulation. A secondary objective is to reconcile previous results based on observations. The analysis is based on a scaling analysis of sea-breeze speed, depth and volume flux. This study is motivated by the fact that the literature of sea breezes interacting with upslope flows is generally qualitative. Results show clear scaling regimes and strong interaction between the two thermally driven circulations. We distinguish three regimes, depending on slope length, slope angle, stability and surface heat flux. The first and third regimes obey the scaling laws of pure sea-breeze scaling. The second regime shows a significant decrease in the scaled volume flux relative to pure sea-breeze scaling. Dynamical relations in the second regime show a strong influence on the circulation of upslope stable air advection.

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Physical Model of Diurnal Heating in the Vicinity of a Two-Dimensional Ridge

Cited by 19 publications

References 0 publications

Separation of upslope flow over a uniform slope

Separation of upslope flow over a uniform slope

Structure of the Atmospheric Boundary Layer in the Vicinity of a Developing Upslope Flow System: A Numerical Model Study

Sea-breeze scaling from numerical model simulations, part II: Interaction between the sea breeze and slope flows

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