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Boundary-Layer Meteorology

, Volume 111, Issue 1, pp 55–84 | Cite as

Mean Flow and Turbulence Characteristics in an Urban Roughness Sublayer

  • Petra Kastner-Klein
  • Mathias W. Rotach
Article

Abstract

In this study, a detailed model of an urban landscape has been re-constructed inthe wind tunnel and the flow structure inside and above the urban canopy has beeninvestigated. Vertical profiles of all three velocity components have been measuredwith a Laser-Doppler velocimeter, and an extensive analysis of the measured meanflow and turbulence profiles carried out. With respect to the flow structure inside thecanopy, two types of velocity profiles can be distinguished. Within street canyons,the mean wind velocities are almost zero or negative below roof level, while closeto intersections or open squares, significantly higher mean velocities are observed.In the latter case, the turbulent velocities inside the canopy also tend to be higherthan at street-canyon locations. For both types, turbulence kinetic energy and shearstress profiles show pronounced maxima in the flow region immediately above rooflevel.

Based on the experimental data, a shear-stress parameterization is proposed, inwhich the velocity scale, us, and length scale, zs, are based on the level and magnitude of the shear stress peak value. In order to account for a flow region inside the canopy with negligible momentum transport, a shear stress displacement height, ds, is introduced. The proposed scaling and parameterization perform well for the measured profiles and shear-stress data published in the literature.

The length scales derived from the shear-stress parameterization also allowdetermination of appropriate scales for the mean wind profile. The roughnesslength, z0, and displacement height, d0, can both be described as fractions of the distance, zs - ds, between the level of the shear-stress peak and the shear-stress displacement height. This result can be interpreted in such a way that the flow only feels the zone of depth zs - ds as the roughness layer. With respect to the lower part of the canopy (z < ds) the flow behaves as a skimming flow. Correlations between the length scales zs and ds and morphometric parameters are discussed.

The mean wind profiles above the urban structure follow a logarithmic windlaw. A combination of morphometric estimation methods for d0 and z0 with wind velocity measurements at a reference height, which allow calculation of the shear-stress velocity, u*, appears to be the most reliable and easiest procedure to determine mean wind profile parameters. Inside the roughnesssublayer, a local scaling approach results in good agreement between measuredand predicted mean wind profiles.

Local scaling Street canyon Urban meteorology Wind profile Wind tunnel 

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References

  1. Andreas, E. L., Claffey K. J., Fairall, C. W., Guest, P. S., Jordan, R. E., and Persson, P. O. G.: 2002, 'Evidence from the Atmospheric Surface Layer that the von Kármán Constant Isn't', in Proceedings of the 15th Symposium on Boundary Layers and Turbulence, Wageningen, The Netherlands, 15-19 July 2002.Google Scholar
  2. Brown, M. J., Lawson, R. E., Descroix, D. S., and Lee, R. L.: 2000, 'Mean Flow and Turbulence Measurements around a 2-D Array of Buildings in a Wind Tunnel', in 11th Conf. on Appl. of Air Poll. Met., Long Beach, CA, U.S.A., January 2000.Google Scholar
  3. Cheng, H. and Castro, I. P.: 2002, 'Near Wall Flow over Urban-Like Roughness', Boundary-Layer Meteorol. 104, 229–259.Google Scholar
  4. Christen, A., Vogt, R., Rotach, M. W., and Parlow, E.: 2002, 'First Results from BUBBLE I: Profiles of Fluxes in the Urban Roughness Sublayer', in Proceedings of the 4th Symposium on the Urban Environment, Norfolk, VA, U.S.A., 20-24 May 2002.Google Scholar
  5. Elliott, W. P.: 1958, 'The Growth of the Atmospheric Internal Boundary Layer', Trans. Amer. Geophys. Union 39, 1048–1054.Google Scholar
  6. Feigenwinter, C., Vogt, R., and Parlow, E.: 1999, 'Vertical Structure of Selected Turbulence Characteristics above an Urban Canopy', Theor. Appl. Climatol. 62, 51–63.Google Scholar
  7. Garratt, J. R.: 1990, 'The Internal Boundary Layer-A Review', Boundary-Layer Meteorol. 50, 171–203.Google Scholar
  8. Grimmond, C. S. B. and Oke, T. R.: 1999, 'Aerodynamic Properties of Urban Areas Derived from Analysis of Surface Form', J. Appl. Meteorol. 38, 1262–1292.Google Scholar
  9. Hussain, M. and Lee, B. E., 1980: 'A Wind Tunnel Study of the Mean Pressure Forces Acting on Large Groups of Low Rise Buildings', J. Wind Eng. Ind. Aerodyn. 6, 207–225.Google Scholar
  10. Jackson, P. S.: 1981, 'On the Displacement Height in the Logarithmic Velocity Profile', J. Fluid Mech. 111, 15–25.Google Scholar
  11. Kaimal, J. C. and Finnigan, J. J.: 1994, Atmospheric Boundary Layer Flows. Their Structure and Measurement, Oxford University Press, U.K., 289 pp.Google Scholar
  12. Kastner-Klein, P.: 1999, Experimentelle Untersuchung der strömungsmechanischen Transportvorgänge in Straßenschluchten, Dissertation, Universität Karlsruhe, Germany.Google Scholar
  13. Kastner-Klein, P., Fedorovich, E., and Rotach, M. W.: 2001, 'AWind Tunnel Study of Organised and Turbulent Air Motions in Urban Street Canyons', J. Wind Eng. Ind. Aerodyn 89, 849–861.Google Scholar
  14. Louka, P.: 1999, Measurements of Airflow in an Urban Environment, Ph.D. Thesis, University of Reading, U.K.Google Scholar
  15. Louka, P., Belcher, S. E., and Harrsion R.G., 2000: 'Coupling between Air Flow in Streets and the Well-Developed Boundary Layer Aloft', Atmos. Environ. 34, 2613–2621.Google Scholar
  16. MacDonald, R.W.: 2000, 'Modelling the Mean Velocity Profile in the Urban Canopy Layer', Boundary-Layer Meteorol. 97, 25–45.Google Scholar
  17. MacDonald, R. W., Carter Schofield, S., and Slawson, P. R.: 2002, 'Turbulence Statistics in the Developing Urban Boundary-Layer', in Proceedings of the 4th Symposium on the Urban Environment, Norfolk, VA, U.S.A., 20-24 May 2002.Google Scholar
  18. MacDonald, R. W., Griffiths, R. S., and Hall D. J.: 1998, 'An Improved Method for the Estimation of Surface Roughness of Obstacle Arrays', Atmos. Environ. 32, 1857–1894.Google Scholar
  19. Martilli, A., Clappier, A., and Rotach, M.W.: 2002, 'An Urban Surface Exchange Parameterisation for Mesoscale Models', Boundary-Layer Meteorol. 104, 261–304.Google Scholar
  20. Oikawa, S. and Meng, Y: 1995,'Turbulence Characteristics and Organized Motion in a Suburban Roughness Sublayer', Boundary-Layer Meteorol. 74, 289–312.Google Scholar
  21. Oncley, S. P., Friehe, C. A., Larue, J. C., Businger, J. A., Itsweire, E. C., and Chang, S. S.: 1996, 'Surface-Layer Fluxes, Profiles and Turbulence Measurements over Uniform Terrain Under Near-Neutral Conditions', J. Atmos. Sci. 53, 1029–1044.Google Scholar
  22. Panofsky, H. A. and Dutton, J. A.: 1984, Atmospheric Turbulence: Models and Methods for Engineering Applications,Wiley-Interscience, New York, 397 pp.Google Scholar
  23. Pendergrass, W. and Arya, S. P. S.: 1984, 'Dispersion in Neutral Boundary Layer over a Step Change in Surface Roughness-I. Mean Flow and Turbulence Structure', Atmos. Environ. 18, 1267–1279.Google Scholar
  24. Plate, E. J.: 1995, 'Urban Climates and Urban Climate Modelling: An Introduction', in J. E. Cermak et al. (eds.), Wind Climate in Cities, Kluwer Academic Publishers, Boston/Dordrecht, pp. 23–29.Google Scholar
  25. Rafailidis, S.: 1997, 'Influence of Building Areal Density and Roof Shape on the Wind Characteristics above a Town', Boundary-Layer Meteorol. 85, 255–271.Google Scholar
  26. Raupach, M. R.: 1980, 'A Wind-Tunnel Study of Turbulent Flow Close to Regularly Arrayed Roughness elements', Boundary-Layer Meteorol. 18, 373–397.Google Scholar
  27. Raupach, M. R., Antonia R. A., and Rajagopalan S.: 1991, 'Rough-Wall Turbulent Boundary Layers', Appl. Mech. Rev. 44, 1–25.Google Scholar
  28. Rotach, M. W.: 1993a, 'Turbulence Close to a Rough Urban Surface, Part I: Reynolds Stress', Boundary-Layer Meteorol. 65, 1–28.Google Scholar
  29. Rotach, M. W.: 1993b, 'Turbulence Close to a Rough Urban Surface, Part II: Variances and Gradients', Boundary-Layer Meteorol. 66, 75–92.Google Scholar
  30. Rotach, M. W.: 1995, 'Profiles of Turbulence Statistics in and above an Urban Street Canyon', Atmos. Environ. 29, 1473–1486.Google Scholar
  31. Rotach, M. W.: 1999, 'On the Influence of the Urban Roughness Sublayer on Turbulence and Dispersion', Atmos. Environ. 33, 4001–4008.Google Scholar
  32. Rotach, M. W.: 2001, 'Simulation of Urban-Scale Dispersion Using a Lagrangian Stochastic Dispersion Model', Boundary-Layer Meteorol. 99, 379–410.Google Scholar
  33. Roth M., 2000: 'Review of Atmospheric Turbulence over Cities', Quart. J. Roy. Meteorol. Soc. 126, 941–990.Google Scholar
  34. Theurer, W.: 1999, 'Typical Building Arrangements for Urban Air Pollution Modelling', Atmos. Environ. 33, 4057–4066.Google Scholar
  35. Vachon, G., Louka, P., Rosant, J-M., Mestayer, P., and Sini, J-F.: 2001, 'Measurements of Traffic-Induced Turbulence within a Street Canyon during the Nantes '99 Experiment', J. Water Air Soil Poll.: Focus 2(5-6), 127–140.Google Scholar
  36. Vachon, G., Rosant, J-M., Mestayer, P., and Sini, J-F.: 1999, 'Measurements of Dynamic and Thermal Field in a Street Canyon, URBCAP Nantes 99', in Proceedings of the 6th International Conference on Harmonisation within Atmospheric Dispersion Modelling, October 11-14, Rouen, France.Google Scholar

Copyright information

© Kluwer Academic Publishers 2004

Authors and Affiliations

  1. 1.School of MeteorologyUniversity of Oklahoma, SEC 1354NormanU.S.A
  2. 2.Institute for Atmospheric and Climate ScienceETH ZurichZurichSwitzerland

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