Nocturnal Wind Direction Shear and Its Potential Impact on Pollutant Transport

Bowen, B.M.; Baars, J. A.; Stone, G.L.

doi:10.1175/1520-0450(2000)039<0437:nwdsai>2.0.co;2

Cited by 19 publications

(11 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…One interesting negative result was the complete lack of a relationship between NLQ and wind directional shear in our findings. Studies of passive material with a heterogeneous source at the ground have shown that material typically becomes layered given the presence of a vertical shear of wind direction; this effect is known as differential advection (Bowen et al, 2000). Because there was no evidence that differential advection was responsible for the layers observed in the present study, this is consistent with the idea that the source populations of migrants are homogenously distributed over large areas (Taylor, 1973).…”

Section: Discussionmentioning

confidence: 99%

Layers of nocturnal insect migrants at high‐altitude: the influence of atmospheric conditions on their formation

Wood

Clark

Barlow

et al. 2010

Agri and Forest Entomology

View full text Add to dashboard Cite

1 Radar studies of nocturnal insect migration have often found that the migrants tend to form well-defined horizontal layers at a particular altitude. 2 In previous short-term studies, nocturnal layers were usually observed to occur at the same altitude as certain meteorological features, most notably at the altitudes of temperature inversion tops or nocturnal wind jets. 3 Statistical analyses are presented of 4 years of data that compared the presence, sharpness and duration of nocturnal layer profiles, observed using continuouslyoperating entomological radar, with meteorological variables at typical layer altitudes over the U.K. 4 Analysis of these large datasets demonstrated that temperature was the foremost meteorological factor that was persistently associated with the presence and formation of longer-lasting and sharper layers of migrating insects over southern U.K.

show abstract

Section: Discussionmentioning

confidence: 99%

Layers of nocturnal insect migrants at high‐altitude: the influence of atmospheric conditions on their formation

Wood

Clark

Barlow

et al. 2010

Agri and Forest Entomology

View full text Add to dashboard Cite

show abstract

“…When atmospheric contaminants are released in a complex terrain area, there is a need to document both local and regional flows, especially for stable conditions when vertical dilution is very weak. Characterizing the stable boundary layer (SBL) is therefore of extreme importance and is viewed as one of the most serious atmospheric conditions for air quality (Zanetti, 1990), especially in complex terrains which modify the flow and strongly influence dispersion (Bowen et al , 2000; Triantafyllou and Kassomenos, 2002; Salmond and McKendry, 2005; Largeron, 2010). Cadarache, one of the research centres of the Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA; the French Alternative Energies and Atomic Energy Commission), is situated in the pre‐alpine area of the Southern Alps in France, where up‐ and down‐valley flows are frequently formed under weak synoptic forcing and clear skies.…”

Section: Introductionmentioning

confidence: 99%

Characterization of valley flows within two confluent valleys under stable conditions: observations from the KASCADE field experiment

Duine

Hedde

Roubin

et al. 2017

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

Wind patterns in main and tributary valley systems undergo diurnal variations that are very dependent on the valley's dimensions. Characterizing the down‐valley winds is important for pollutant dispersion studies. It is also a challenge for numerical simulations. This paper uses KASCADE (KAtabatic winds and Stability over CAdarache for Dispersion of Effluents) observations to describe down‐valley flow development and characteristics in two intersecting, shallow valleys of different sizes located in the pre‐alpine region of southeast France. The Durance Valley and its tributary valley, the Cadarache Valley, are different in depth (200 and 100 m depth, respectively), slope (0.2 and 1.2°), width (5–8 and 1–2 km) and length (>50 and 6 km). Both down‐valley flows were dominant features for the period of measurements. The distinct valley scales lead to different characteristics: the smaller Cadarache down‐valley wind is primarily thermally driven and attains wind speeds of up to 1–4 m s−1 with its jet nose at around 30 m in height above ground. The flow at that height initiates 2 h after sensible heat flux turnover, a time‐scale which relates to a linear wave solution for along‐valley winds. The Durance down‐valley wind involves larger scales –for both terrain features and large‐scale circulation –and is related to a mountain‐to‐plain circulation. Therefore its onset occurs with a delay of ∼6 h after sunset. It reaches speeds of 4–8 m s−1 and a depth of 175–225 m above ground. Its highest occurrence is just after sunrise. Between the two valley winds, a shear layer is observed, the origin of which could be a combination of a Cadarache valley flow return current and a Durance down‐valley wind stream redirected by orography.

show abstract

“…A number of studies have indicated that intermittency is driven by nonstationarity due to motion on timescales that are slightly greater than those for turbulence (Mahrt, 2007a(Mahrt, , 2010b when the large-scale flow is weak. These motions are sometimes referred to as submesoscale motions (Nappo, 2002;Sun et al, 2004;Anfossi et al, 2005;Conangla et al, 2008;Mahrt et al, 2008). Some studies have simply defined intermittency as "another name for nonstationary" (Treviño, 2000).…”

mentioning

confidence: 99%

Effects of turbulence structure and urbanization on the heavy haze pollution process

et al. 2019

View full text Add to dashboard Cite

Abstract. In this paper, an automated algorithm is developed, which is used to identify the spectral gap during the heavy haze pollution process, reconstruct acquired data, and obtain pure turbulence data. Comparisons of the reconstructed turbulent flux and eddy covariance (EC) flux show that there are overestimations regarding the exchange between the surface and the atmosphere during heavy haze pollution episodes. After reconstruction via the automated algorithm, pure turbulence data can be obtained. We introduce a definition to characterize the local intermittent strength of turbulence (LIST). The trend in the LIST during pollution episodes shows that when pollution is more intense, the LIST is smaller, and intermittency is stronger; when pollution is weaker, the LIST is larger, and intermittency is weaker. At the same time, the LIST at the city site is greater than at the suburban site, which means that intermittency over the complex city area is weaker than over the flat terrain area. Urbanization seems to reduce intermittency during heavy haze pollution episodes, which means that urbanization reduces the degree of weakening in turbulent exchange during pollution episodes. This result is confirmed by comparing the average diurnal variations in turbulent fluxes at urban and suburban sites during polluted and clean periods. The sensible heat flux, latent heat flux, momentum flux, and turbulent kinetic energy (TKE) in urban and suburban areas are all affected when pollution occurs. Material and energy exchanges between the surface and the atmosphere are inhibited. Moreover, the impact of the pollution process on suburban areas is much greater than on urban areas. The turbulent effects caused by urbanization seem to help reduce the consequences of pollution under the same weather and pollution source condition, because the turbulence intermittency is weaker, and the reduction in turbulence exchange is smaller over the urban underlying surface.

show abstract

Nocturnal Wind Direction Shear and Its Potential Impact on Pollutant Transport

Cited by 19 publications

References 9 publications

Layers of nocturnal insect migrants at high‐altitude: the influence of atmospheric conditions on their formation

Layers of nocturnal insect migrants at high‐altitude: the influence of atmospheric conditions on their formation

Characterization of valley flows within two confluent valleys under stable conditions: observations from the KASCADE field experiment

Effects of turbulence structure and urbanization on the heavy haze pollution process

Contact Info

Product

Resources

About