On plume meandering under stable stratification

Etling, Dieter

doi:10.1016/0960-1686(90)90232-c

Cited by 58 publications

(26 citation statements)

References 28 publications

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“…The meandering of plumes in stable conditions has been well documented by a number of authors (Kristensen et al, 1981;Hanna, 1983;Etling, 1990;Eskridge et al, 1990). Under stable stratification, vertical motions are suppressed by the buoyancy forces and, due to the three-dimensional nature of small-scale turbulence, the horizontal turbulent motions are also reduced.…”

Section: Plume Meandering and Stationaritymentioning

confidence: 83%

Concentration fluctuation measurements in a plume dispersing in a stable surface layer

Mylne

1992

Boundary-Layer Meteorol

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A set of tracer experiments studying concentration fluctuations in a pollutant plume dispersing near the surface in a stably stratified nocturnal boundary layer is described, and the results are compared with those obtained in near-neutral stability conditions by Mylne and Mason (1991). The results highlight the importance of slow meandering of the plume which is characteristic of stable conditions. This meandering makes it impossible to conduct experiments under near-stationary conditions, resulting in considerable statistical variability in the results, but is important in reducing timeaveraged concentrations.Spectral characteristics of the plume and general fluctuation statistics are qualitatively similar to those in near-neutral stability, but there are significant quantitative differences. Fluctuation time scales are shown to be substantially longer under stable conditions. This difference cannot be fully explained by the reduced windspeed alone, indicating that the length scale of plume elements is also longer. Some of the differences observed in stable conditions, particularly the longer time scales, are shown to substantially increase the potential hazard due to fluctuations in practical applications. A conceptual model of plume dispersion is described, which explains the observed plume structure under different conditions by relating it to the turbulent velocity spectra.

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Section: Plume Meandering and Stationaritymentioning

confidence: 83%

Concentration fluctuation measurements in a plume dispersing in a stable surface layer

Mylne

1992

Boundary-Layer Meteorol

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“…These meanders are often observed under stable conditions and low wind intensities [48]. They may influence pollutant dispersion and may also be one of the sources of the oscillations observed in Figure 9.…”

Section: Megève Valleymentioning

confidence: 99%

Wintertime Local Wind Dynamics from Scanning Doppler Lidar and Air Quality in the Arve River Valley

et al. 2018

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Air quality issues are frequent in urbanized valleys, particularly in wintertime when a temperature inversion forms and the air within the valley is stably stratified over several days. In addition to pollutant sources, local winds can have a significant impact on the spatial distribution and temporal evolution of pollutant concentrations. They can be very complex and difficult to represent in numerical weather prediction models, particularly under stable conditions. Better knowledge of these local winds from observations is also a prerequisite to improving air quality prediction capability. This paper analyses local winds during the Passy-2015 field experiment that took place in a section of the Arve river valley, near Chamonix-Mont-Blanc. This location is one of the worst places in France regarding air quality. The wind analysis, which is mainly based on scanning Doppler lidar data sampling a persistent temperature inversion episode, reveals features consistent with the higher pollutant concentrations observed in this section of the valley as well as their spatial heterogeneities. In particular, an elevated down-valley jet is observed at night in the northern half of the valley, which, combined with a weak daytime up-valley wind, leads to very poor ventilation of the lowest layers. A northeast-southwest gradient in ventilation is observed on a daily-average, and is consistent with the PM10 heterogeneities observed within the valley.

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“…Such motions are always present and cause the flow to be significantly non-stationary when the large-scale flow is weak. This non-stationarity is often visualized in terms of large variations of the wind direction on time scales of tens of minutes (Hanna 1986;Etling 1990;Anfossi et al 2005) and large abrupt shifts of wind direction on time scales of a minute or less (Mahrt 2008). In the stable boundary layer, non-stationary submeso motions on time scales of minutes or tens of minutes include wave-like phenomena (e.g., Fritts et al 2003), two-dimensional modes, non-stationary drainage flows (Doran and Horst 1981), microfronts, propagating density currents and solitary waves (Sun et al , 2004Anderson 2003;Terradellas et al 2005) and a variety of other more complex modes (Mahrt 2007a).…”

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confidence: 99%

Variability and Maintenance of Turbulence in the Very Stable Boundary Layer

Mahrt

2009

Boundary-Layer Meteorol

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The relationship of turbulence quantities to mean flow quantities, such as the Richardson number, degenerates substantially for strong stability, at least in those studies that do not place restrictions on minimum turbulence or non-stationarity. This study examines the large variability of the turbulence for very stable conditions by analyzing four months of turbulence data from a site with short grass. Brief comparisons are made with three additional sites, one over short grass on flat terrain and two with tall vegetation in complex terrain. For very stable conditions, any dependence of the turbulence quantities on the mean wind speed or bulk Richardson number becomes masked by large scatter, as found in some previous studies. The large variability of the turbulence quantities is due to random variations and other physical influences not represented by the bulk Richardson number. There is no critical Richardson number above which the turbulence vanishes. For very stable conditions, the record-averaged vertical velocity variance and the drag coefficient increase with the strength of the submeso motions (wave motions, solitary waves, horizontal modes and numerous more complex signatures). The submeso motions are on time scales of minutes and not normally considered part of the mean flow. The generation of turbulence by such unpredictable motions appears to preclude universal similarity theory for predicting the surface stress for very stable conditions. Large variation of the stress direction with respect to the wind direction for the very stable regime is also examined. Needed additional work is noted.

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On plume meandering under stable stratification

Cited by 58 publications

References 28 publications

Concentration fluctuation measurements in a plume dispersing in a stable surface layer

Concentration fluctuation measurements in a plume dispersing in a stable surface layer

Wintertime Local Wind Dynamics from Scanning Doppler Lidar and Air Quality in the Arve River Valley

Variability and Maintenance of Turbulence in the Very Stable Boundary Layer

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