The Role of Surface Friction in Downslope Windstorms

Richard, Évelyne; Mascart, Patrick; Nickerson, Everett C.

doi:10.1175/1520-0450(1989)028<0241:trosfi>2.0.co;2

Cited by 76 publications

(43 citation statements)

References 15 publications

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“…A few studies specifically addressing boundary layer effects are mentioned next. Richard et al [155] investigated the effect of friction in downslope windstorms over 2D orography using a hydrostatic numerical model with a turbulent kinetic energy parametrization, finding that it delays the onset of strong surface winds and prevents the downstream propagation of the zone of maximum wind speed. The drag in the corresponding high-states was seen to be established over a longer time interval, with a somewhat lower steady value than in inviscid flow (see Figure 15).…”

Section: Boundary Layer Effectsmentioning

confidence: 99%

“…They showed that the form drag first increases with stability due to increased shear in FIGURE 15 | Time evolution of the drag for simulations of flow over 2D orography using free-slip and no-slip lower boundary conditions (see curve labels details). Reproduced from Figure 4 of Richard et al [155]. © American Meteorological Society.…”

Section: Boundary Layer Effectsmentioning

confidence: 99%

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The physics of orographic gravity wave drag

Teixeira

2014

Front. Phys.

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The drag and momentum fluxes produced by gravity waves generated in flow over orography are reviewed, focusing on adiabatic conditions without phase transitions or radiation effects, and steady mean incoming flow. The orographic gravity wave drag is first introduced in its simplest possible form, for inviscid, linearized, non-rotating flow with the Boussinesq and hydrostatic approximations, and constant wind and static stability. Subsequently, the contributions made by previous authors (primarily using theory and numerical simulations) to elucidate how the drag is affected by additional physical processes are surveyed. These include the effect of orography anisotropy, vertical wind shear, total and partial critical levels, vertical wave reflection and resonance, non-hydrostatic effects and trapped lee waves, rotation and nonlinearity. Frictional and boundary layer effects are also briefly mentioned. A better understanding of all of these aspects is important for guiding the improvement of drag parametrization schemes.

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Section: Boundary Layer Effectsmentioning

confidence: 99%

Section: Boundary Layer Effectsmentioning

confidence: 99%

The physics of orographic gravity wave drag

Teixeira

2014

Front. Phys.

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“…Our selection is not meant to cover all the interesting areas of mountain wave research. At least since the work of Richard et al (1989), it has been recognized that the atmospheric BL can reduce the amplitude of terrain-generated waves. Ólafsson and Bougeault (1997) extended this work with a systematic numerical study of BL effects, including the influence of the Coriolis force.…”

Section: Pre-map Theoretical and Numerical Studiesmentioning

confidence: 99%

Alpine gravity waves: Lessons from MAP regarding mountain wave generation and breaking

Smith

Doyle

Jiang

et al. 2007

Quart J Royal Meteoro Soc

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ABSTRACT:The two-month special observing period of the Mesoscale Alpine Programme (MAP) in autumn 1999 included a variety of complex mountain wave events. Seven wave events were carefully analyzed, compared with numerical models and described in published papers. These detailed investigations revealed some common dynamical elements, i.e. the importance of low-level processes involving the slow-moving boundary layer, low-level wind shear causing either wave absorption or decoupling/spilling, upstream blocking, and latent heat release. Based on these studies, it is clear that any quantitative prediction of mountain wave generation must take full account of these lower troposphere processes. The newest numerical models show significant skill in simulating these effects. Using these models, the climatology of waves over the Alps can be studied.

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“…The neglect of the surface friction appears to create large quantitative differences. Recently Richard et al (1989) and Saito and Ikawa (1990) have reported that surface friction delays the onset of strong surface winds and also prevents the downstream propagation of the hydraulic jump. The results of the three-dimensional simulation of the Yamaji-kaze, including physical processes, will be reported at a later date.…”

Section: Summary and Concluding Remarksmentioning

confidence: 99%

A Numerical Study of the Local Downslope Wind "Yamaji-kaze" in Japan

Saitō¹,

Ikawa²

1991

Journal of the Meteorological Society of Japan

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In order to study the Yamaji-kaze-a typical downslope wind found in Japan, the two-dimensional flow over an asymmetric mountain is simulated by use of a non-hydrostatic model. The Yamajikaze front and the reversed wind behind the front-characteristic features of the Yamaji-kaze-are explained in terms of the internal hydraulic jump and its associated circulation.Numerical experiments for a homogeneous atmosphere show that the behavior of the internal hydraulic jump is significantly affected by the inverse Froude number and the shape of the mountain. When the inverse Froude number is large, a quasi-steady state solution such that the hydraulic jump remains on the lee side of mountain is obtained, with the associated reversed flow being generated just behind the hydraulic jump. In the case of the Yamaji-kaze, the asymmetry of the Shikoku Mountains and the blocking effect of the Chugoku Mountains impede the propagation of the Yamaji-kaze front and allow the reversed wind to occur more readily.For the case of the Yamaji-kaze observed on 21 April 1987, a notable inversion layer was found at a level near the mountaintop. It is confirmed, by numerical experiments of a heterogeneous atmosphere with the observed thermal stratification, that the surface wind strengthens in the presence of the inversion when compared to that without the inversion. Development and propagation of an internal hydraulic jump are qualitatively simulated under the observed thermal stratification and timechanging wind profile. On the basis of the experimental results a conceptual model of the Yamaji-kaze is proposed.

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The Role of Surface Friction in Downslope Windstorms

Cited by 76 publications

References 15 publications

The physics of orographic gravity wave drag

The physics of orographic gravity wave drag

Alpine gravity waves: Lessons from MAP regarding mountain wave generation and breaking

A Numerical Study of the Local Downslope Wind "Yamaji-kaze" in Japan

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