On the Effect of Steep Slope Orientation on the Intensity of Daytime Upslope Flow

Segal, M.; Ookouchi, Yasumasa; Plelke, R. A.

doi:10.1175/1520-0469(1987)044<3587:oteoss>2.0.co;2

Cited by 15 publications

(7 citation statements)

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“…First, upslope winds evolve asymmetrically in the morning according to the times of local sunrise on the respective sidewalls. The effects of this asymmetry on dynamics and air pollution have been noted in both observational (e.g., Gudiksen and Shearer 1989;Orgill 1989;Gohm et al 2009) and modeling studies (e.g., Segal et al 1987;Anquetin et al 1998;Colette et al 2003;Lehner and Gohm 2010). Second, a horizontal temperature and, thus, pressure gradient develops across the valley, producing a cross-valley wind that is directed toward the sunlitwarmer sidewall.…”

Section: Introductionmentioning

confidence: 96%

Diurnal Cycle of Thermally Driven Cross-Basin Winds in Arizona’s Meteor Crater

Lehner

Whiteman

Hoch

2011

Journal of Applied Meteorology and Climatology

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Cross-basin winds produced by asymmetric insolation of the crater sidewalls occur in Arizona's Meteor Crater on days with weak background winds. The diurnal cycle of the cross-basin winds is analyzed together with radiation, temperature, and pressure measurements at the crater sidewalls for a 1-month period. The asymmetric irradiation causes horizontal temperature and pressure gradients across the crater basin that drive the cross-basin winds near the crater floor. The horizontal temperature and pressure gradients and wind directions change as the sun moves across the sky, with easterly winds in the morning and westerly winds in the evening. A case study of 12 October 2006 further illustrates the obtained relation between these parameters for an individual day. The occurrence of an elevated cross-basin flow on 23 October 2006 is shown to relate to the presence of an elevated inversion layer.

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Section: Introductionmentioning

confidence: 96%

Diurnal Cycle of Thermally Driven Cross-Basin Winds in Arizona’s Meteor Crater

Lehner

Whiteman

Hoch

2011

Journal of Applied Meteorology and Climatology

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“…The basic flow features, described at the beginning of this section, were captured despite the simplicity of his model. Segal et al (1987) focused on the effects related to the slope orientation on anabatic flows, which becomes important especially for midlatitude winter conditions. Ye et al (1987) developed a numerical model to extend and validate their theoretical work.…”

Section: Introductionmentioning

confidence: 99%

High-Resolution Numerical Modeling of Thermally Driven Slope Winds in a Valley with Strong Capping

Catalano

Cenedese

2010

Journal of Applied Meteorology and Climatology

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The complete day-night cycle of the circulation over a slope under simplified idealized boundary conditions is investigated by means of large-eddy simulations (LES). The thermal forcing is given with a time-varying law for the surface temperature. A surface layer parameterization based on the Monin-Obukhov similarity theory is used as a wall layer model. The domain geometry is symmetric, having an infinitely long straight valley in the y direction. Since the depth of the katabatic flow in midlatitude climates is limited to 5-30 m, the authors introduced a vertically stretched grid to obtain a finer mesh near the ground. The length scale for the calculation of eddy viscosities is modified to take into account the grid anisotropy. A preintegration of 24 h is made to obtain a capping inversion over the valley. Results show that the model is able to reproduce microscale circulation dynamics driven by thermal forcing over sloping terrain. The diurnal growth of the convective boundary layer leading to the development of the anabatic wind as well as the evolution of the cold pool in the valley during the night and its interaction with the katabatic flow are shown. Waves develop at the interface between the anabatic current and the return flow. During the day, as a combined effect of the geometry and the forcing, a horizontal breeze develops directed from the middle of the valley toward the ridges. The impact of the gravity current on the quiescent atmosphere in the valley generates a weak hydraulic jump during the night.

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“… Schumann [1990] ran an LES of an infinite slope under steady‐state conditions producing results in good agreement with Prandtl 's [1952] analytical solution. Analytical models and their numerical solution require restrictive assumptions and boundary conditions [ Egger , 1981; Petkovšek , 1982; Vergeiner , 1982; Kondo , 1984; Brehm , 1986; Segal et al , 1987; Ye et al , 1987; Haiden , 1990, 2003; Ingel ', 2000]. Water tank models are limited by their simple topography, restricted by side and end walls, and their scaling poses an additional challenge.…”

Section: Introductionmentioning

confidence: 99%

Water tank studies of atmospheric boundary layer structure and air pollution transport in upslope flow systems

2007

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[1] Heated mountain slopes sometimes vent air pollutants out of the boundary layer over the slope top and at other times trap pollutants in closed circulations. Field, numerical, and water tank studies of fair weather atmospheric conditions over complex terrain have shown more complicated vertical distributions of temperature, moisture, and aerosols than over horizontal terrain. To study these phenomena, we analyze flow fields, densities, and dye distributions in a bottom-heated salt-stratified water tank over a 19°slope with adjacent plain and plateau and compare with field and numerical model data. Vertical layering of dye results from upslope and plain-plateau circulations. The thermal boundary layer (TBL, the bottom layer up to neutral buoyancy height), coincides with the lower branches of these circulations. The return flow branches form elevated layers (EL) with properties intermediate between the TBL and environmental background. As heating continues, the TBL rapidly entrains the ELs, leading to deeper circulations with new ELs at greater heights. Field data suggest that successive formation and entrainment of ELs occurs at multiple scales in the atmosphere. If the aerosol loading of an EL is too high to distinguish it from the underlying TBL on lidar backscatter scans, then both layers and the associated closed circulation appear embedded in one deep backscatter boundary layer. The findings suggest defining the atmospheric boundary layer in complex terrain on the diurnal heating timescale rather than the commonly used 1-hour timescale, which is more appropriate for flat terrain. We discuss conditions leading to venting versus trapping of air pollutants.Citation: Reuten, C., D. G. Steyn, and S. E. Allen (2007), Water tank studies of atmospheric boundary layer structure and air pollution transport in upslope flow systems,

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On the Effect of Steep Slope Orientation on the Intensity of Daytime Upslope Flow

Cited by 15 publications

References 0 publications

Diurnal Cycle of Thermally Driven Cross-Basin Winds in Arizona’s Meteor Crater

Diurnal Cycle of Thermally Driven Cross-Basin Winds in Arizona’s Meteor Crater

High-Resolution Numerical Modeling of Thermally Driven Slope Winds in a Valley with Strong Capping

Water tank studies of atmospheric boundary layer structure and air pollution transport in upslope flow systems

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