Abstract
The mean flow within inhomogeneous urban areas is investigated using an urban canopy model. The urban canopy model provides a conceptual and computational tool for representing urban areas in a way suitable for parameterisation within numerical weather prediction and urban air quality models. Average aerodynamic properties of groups of buildings on a neighbourhood scale can be obtained in terms of the geometry and layout of the buildings. These canopy parameters then determine the spatially averaged mean wind speeds within the canopy as a whole. Using morphological data for real cities, computations are performed for representative sections of cities. Simulations are performed to study transitions between different urban neighbourhoods, such as residential areas and city centres. Such transitions are accompanied by changes in mean building density and building height. These are considered first in isolation, then in combination, and the generic effects of each type of change are identified. The simulation of winds through a selection of downtown Los Angeles is considered as an example. An increase in canopy density is usually associated with a decrease in the mean wind speed. The largest difference between mean winds in canopies of different densities occurs near ground level. Winds generally decrease upon encountering a taller canopy of the same density, but this effect may be reversed very near the ground, with possible speed-ups if the canopy is especially tall. In the vicinity of a transition there is an overshoot in the mean wind speed in the bottom part of the canopy. Mechanisms for these effects are discussed.
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References
S. E. Belcher N. Jerram J. C. R. Hunt (2003) ArticleTitle‘Adjustment of the Atmospheric Boundary Layer to a Canopy of Roughness Elements’ J. Fluid Mech 488 369–398
R. D. Bornstein D. S. Johnson (1976) ArticleTitle‘Urban-Rural Wind Velocity Differences’ Atmos. Environ 11 597–604
M. Bottema (1999) ArticleTitle‘Towards Rules of Thumb for Wind Comfort and Air Quality’ Atmos. Environ 33 4009–4017
R. E. Britter S. R. Hanna (2003) ArticleTitle‘Flow and Dispersion in Urban Areas’ Annu. Rev. Fluid Mech 35 469–496
R. E. Britter J. C. R. Hunt (1979) ArticleTitle‘Velocity Measurements and Order of Magnitude Estimates of the Flow between Two Buildings in a Simulated Atmospheric Boundary Layer’ J. Indust. Aerodyn 4 165–182
Brown, M.: 2000, ‘Urban Parameterisations for Mesoscale Meteorological Models’, in Z. Boybeyi (ed.),Mesoscale Atmospheric Dispersion, Wessex Press, pp. 193–255.
S. Burian M. Brown S. Linger (2002) Morphological Analyses Using 3D Building Databases Los Alamos National Laboratory Los Angeles,CA
H. Cheng I.P. Castro (2002a) ArticleTitle‘Near Wall Flow over Urban-Like Roughness’ Boundary-Layer Meteorol. 104 229–259
H. Cheng I.P. Castro (2002b) ArticleTitle‘Near-Wall Flow Development after a Step Change in Surface Roughness’ Boundary-Layer Meteorol. 105 411–432
R. M. Cionco (1965) ArticleTitle’A Mathematical Model for Air Flow in a Vegetative Canopy’ J. Appl. Meteorol 4 517–522
O. Coceal S. E. Belcher (2004) ArticleTitle’A Canopy Model of Mean Winds through Urban Areas’ Quart. J. Roy. Meteorol. Soc 130 1349–1372
J. J. Finnigan (1985) ‘Turbulent Transport in Flexible Plant Canopies’ B. A. Hutchinson B. B. Hicks (Eds) The Forest Atmosphere Interaction Reidel Dordrecht 443–480
J. J. Finnigan (2000) ArticleTitle‘Turbulence in Plant Canopies’ Annu. Rev. Fluid Mech 32 519–572
Gandemer, J.: 1976, ‘Wind Environment around Buildings; Aerodynamic Concepts’, in Proceedings of the 4th International Conference on Wind Effects on Buildings and Structures, London, 1975. Cambridge University Press, pp. 423–432.
C.S.B. Grimmond T.R. Oke (1999) ArticleTitle‘Aerodynamic Properties of Urban Areas Derived From Analysis of Surface Form’ J. Appl. Meteorol 38 1262–1292
Hunt, J. C. R.: 1975, ‘Fundamental Studies of Flow near Buildings’, in Proceedings of the Conference on Wind Effects on Models and Systems in Architecture and Building, Sept. 1973. Medical and Technical Publishing, Lancaster, U.K., pp. 101–109.
Isyumov, N. and Davenport, A. G.: 1976, ‘The Ground Level Wind Environment in Built Up Areas’, in Proceedings of the 4th International Conference on Wind Effects on Buildings and Structures, London, 1975. Cambridge University Press, pp. 403–422.
Lawson, T. V. and Penwarden, A. D.: 1976, ‘The Effect of Wnd on People in the Vicinity of Buildings’, in Proceedings of the 4th International Conference on Wind Effects on Buildings and Structures, London, 1975. Cambridge University Press, pp. 605–622.
J. A. Leene (1992) ArticleTitle‘Building Wake Effects in Complex Situations’ J. Indust. Aerodyn 41 2277–2288
R. W. Macdonald (2000) ArticleTitle‘Modelling the Mean Velocity Profile in the Urban Canopy Layer’ Boundary-Layer Meteorol 97 25–45
Macdonald, R. W., Carter, S., and Slawson, P. R.: 2000, Measurements of Mean Velocity and Turbulence Statistics in Simple Obstacle Arrays at 1:200 Scale, Thermal Fluids Report 2000-01, University of Waterloo, 130 pp.
R. W. Macdonald R. F. Griffiths D. J. Hall (1998) ArticleTitle‘An Improved Method for the Estimation of Surface Roughness of Obstacle Arrays’ Atmos. Environ 32 1857–1864
A. Martilli A. Clappier M. W. Rotach (2002) ArticleTitle‘An Urban Surface Exchange Parameterisation for Mesoscale Models’ Boundary-Layer Meteorol 104 261–304
M. R. Raupach R. H. Shaw (1982) ArticleTitle‘Averaging Procedures for Flow within Vegetation Canopies’ Boundary-Layer Meteorol 22 79–90
M. R. Raupach R. A. Antonia S. Rajagopalan (1991) ArticleTitle‘Rough-Wall Turbulent Boundary Layers’ Appl. Mech. Rev 44 1–25 Occurrence Handle10.1115/1.3119492
M. R. Raupach J. J. Finnigan Y. Brunet (1996) ArticleTitle‘Coherent Eddies and Turbulence in Vegetation Canopies: The Mixing Layer Analogy’ Boundary-Layer Meteorol 78 351–382
M. W. Rotach (1995) ArticleTitle‘Profiles of Turbulence Statistics in and above an Urban Street Canyon’ Atmos. Environ 29 1473–1486
M. W. Rotach (1999) ArticleTitle‘On the Influence of the Urban Roughness Sublayer on Turbulence and Dispersion’ Almos. Environ 33 4001–4008
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Coceal, O., Belcher, S.E. Mean Winds Through an Inhomogeneous Urban Canopy. Boundary-Layer Meteorol 115, 47–68 (2005). https://doi.org/10.1007/s10546-004-1591-4
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DOI: https://doi.org/10.1007/s10546-004-1591-4