In-Street Wind Direction Variability in the Vicinity of a Busy Intersection in Central London

• Published in: Boundary-layer meteorology Vol. 136; no. 3; pp. 489 - 513
• Main Authors: Balogun, Ahmed A, Tomlin, Alison S, Wood, Curtis R, Barlow, Janet F, Belcher, Stephen E, Smalley, Robert J, Lingard, Justin J. N, Arnold, Sam J, Dobre, Adrian, Robins, Alan G, Martin, Damien, Shallcross, Dudley E
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : Springer Netherlands 01-09-2010; Springer Netherlands; Springer; Springer Nature B.V
• Subjects: Air pollution; Atmospheric boundary layer; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Bifurcations; Channelling; Convection, turbulence, diffusion. Boundary layer structure and dynamics; DAPPLE field campaign; Dispersion; Dispersions; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Exact sciences and technology; External geophysics; Flow bifurcation; Flow channelling; Flow pattern; Intersections; Masking; Meteorology; Recirculation; Turbulence; Urban areas; Urban intersection; Wind; Wind direction; Wind measurement; United Kingdom > UK; England; London England; British Isles, England, Greater London, London; Recirculation; Flow bifurcation; Flow channelling; Urban intersection; DAPPLE field campaign; Dispersion; Data analysis; time scales; time variations; Acoustic anemometer; Bifurcation; Oblique flow; urban areas; Street canyon; winds; Air pollution; Height; flow field
• ISSN: 0006-8314; 1573-1472
• DOI: 10.1007/s10546-010-9515-y

We present results from fast-response wind measurements within and above a busy intersection between two street canyons (Marylebone Road and Gloucester Place) in Westminster, London taken as part of the DAPPLE (Dispersion of Air Pollution and Penetration into the Local Environment; www.dapple.org.uk ) 2007 field campaign. The data reported here were collected using ultrasonic anemometers on the roof-top of a building adjacent to the intersection and at two heights on a pair of lamp-posts on opposite sides of the intersection. Site characteristics, data analysis and the variation of intersection flow with the above-roof wind direction (θ ref ) are discussed. Evidence of both flow channelling and recirculation was identified within the canyon, only a few metres from the intersection for along-street and across-street roof-top winds respectively. Results also indicate that for oblique roof-top flows, the intersection flow is a complex combination of bifurcated channelled flows, recirculation and corner vortices. Asymmetries in local building geometry around the intersection and small changes in the background wind direction (changes in 15- min mean θ ref of 5°-10°) were also observed to have profound influences on the behaviour of intersection flow patterns. Consequently, short time-scale variability in the background flow direction can lead to highly scattered in-street mean flow angles masking the true multi-modal features of the flow and thus further complicating modelling challenges.