Gravity-Wave Drag in the Stable Boundary Layer Over Moderate Terrain

City centers have to cope with an increasing amount of air pollution. The supply of fresh air is crucial yet difficult to ensure, especially under stable conditions of the atmospheric boundary layer. This case study used the PArallelized Large eddy simulation (LES) Model PALM to investigate the wind field over an urban lake that had once been built as a designated fresh air corridor for the city center of Münster, northwest, Germany. The model initialization was performed using the main wind direction and stable boundary layer conditions as input. The initial wind and temperature profiles included a weak nocturnal low-level jet. By emitting a passive scalar at one point on top of a bridge, the dispersion of fresh air could be traced over the lake’s surface, within street canyons leading to the city center and within the urban boundary layer above. The concept of city ventilation was confirmed in principle, but the air took a direct route from the shore of the lake to the city center above a former river bed and its adjoining streets rather than through the street canyons. According to the dispersion of the passive scalar, half of the city center was supplied with fresh air originating from the lake. PALM proved to be a useful tool to study fresh air corridors under stable boundary layer conditions.

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Thermal Submeso Motions in the Nocturnal Stable Boundary Layer. Part 2: Generating Mechanisms and Implications

Boundary-Layer Meteorology ◽

10.1007/s10546-021-00619-z ◽

2021 ◽

Author(s):

Lena Pfister ◽

Karl Lapo ◽

Larry Mahrt ◽

Christoph K. Thomas

Keyword(s):

Boundary Layer ◽

Stable Boundary Layer ◽

Side Wall ◽

Cold Pool ◽

Continuous Data ◽

Valley Bottom ◽

Near Surface ◽

Cold Air ◽

Stable Boundary ◽

Surface Temperatures

AbstractIn the stable boundary layer, thermal submesofronts (TSFs) are detected during the Shallow Cold Pool experiment in the Colorado plains, Colorado, USA in 2012. The topography induces TSFs by forming two different air layers converging on the valley-side wall while being stacked vertically above the valley bottom. The warm-air layer is mechanically generated by lee turbulence that consistently elevates near-surface temperatures, while the cold-air layer is thermodynamically driven by radiative cooling and the corresponding cold-air drainage decreases near-surface temperatures. The semi-stationary TSFs can only be detected, tracked, and investigated in detail when using fibre-optic distributed sensing (FODS), as point observations miss TSFs most of the time. Neither the occurrence of TSFs nor the characteristics of each air layer are connected to a specific wind or thermal regime. However, each air layer is characterized by a specific relationship between the wind speed and the friction velocity. Accordingly, a single threshold separating different flow regimes within the boundary layer is an oversimplification, especially during the occurrence of TSFs. No local forcings or their combination could predict the occurrence of TSFs except that they are less likely to occur during stronger near-surface or synoptic-scale flow. While classical conceptualizations and techniques of the boundary layer fail in describing the formation of TSFs, the use of spatially continuous data obtained from FODS provide new insights. Future studies need to incorporate spatially continuous data in the horizontal and vertical planes, in addition to classic sensor networks of sonic anemometry and thermohygrometers to fully characterize and describe boundary-layer phenomena.

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The Height Correction of Similarity Functions in the Stable Boundary Layer

Boundary-Layer Meteorology ◽

10.1007/s10546-011-9653-x ◽

2011 ◽

Vol 142 (1) ◽

pp. 21-31 ◽

Cited By ~ 18

Author(s):

Zbigniew Sorbjan

Keyword(s):

Boundary Layer ◽

Stable Boundary Layer ◽

Similarity Functions ◽

Stable Boundary

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Simulations of atmospheric dispersion in an urban stable boundary layer

International Journal of Environment and Pollution ◽

10.1504/ijep.2001.000600 ◽

2001 ◽

Vol 16 (1/2/3/4/5/6) ◽

pp. 1 ◽

Cited By ~ 5

Author(s):

E. Ferrero ◽

D. Anfossi ◽

G. Tinarelli

Keyword(s):

Boundary Layer ◽

Stable Boundary Layer ◽

Atmospheric Dispersion ◽

Stable Boundary

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Tethered Balloon Observations Of The Nocturnal Stable Boundary Layer In A Valley

Boundary-Layer Meteorology ◽

10.1023/a:1002628924673 ◽

2000 ◽

Vol 97 (1) ◽

pp. 1-24 ◽

Cited By ~ 22

Author(s):

J. J. Holden ◽

S. H. Derbyshire ◽

S. E. Belcher

Keyword(s):

Boundary Layer ◽

Stable Boundary Layer ◽

Tethered Balloon ◽

Stable Boundary

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