Advertisement

Boundary-Layer Meteorology

, Volume 127, Issue 2, pp 173–191 | Cite as

Relating Urban Surface-layer Structure to Upwind Terrain for the Salford Experiment (Salfex)

  • J. F. Barlow
  • G. G. Rooney
  • S. von Hünerbein
  • S. G. Bradley
Original Paper

Abstract

Profiles of wind and turbulence over an urban area evolve with fetch in response to surface characteristics. Sodar measurements, taken on 22 April 2002 during the Salford Experiment in the UK (Salfex), are here related to upstream terrain. A logarithmic layer up to z = 65m was observed in all half-hour averaged profiles. Above this height the profile showed a different vertical gradient, suggesting a change in surface cover upstream. The drag coefficient varied by a factor of two over only a 20° direction change. Turbulence intensity (σ x ) for each wind component (x) decreased with height, but the ratio suggested an underestimate of σ u compared to previous results. Mean urban and suburban cover fraction within the source area for each height decreased sharply between z = 20 and 50m, increasing slightly above. The near-convergence of cover fractions thus occured for source areas of minimum length ≈ 2,200 m. In comparison, the mean length scale of heterogeneity L P was calculated from surface cover data to be 1,284 m, and the corresponding mean blending height h b was 175 m. Finally, the mean streamline angle, α, was negative and the magnitude decreased with height. An exponential fit to α for z ≤ 65m gave an e-folding height scale of 159 m. A simple relationship between this height scale and L P was assumed, giving L P ≈ 1,080 m, which is in reasonable agreement with the estimate from surface cover type. The results suggest that more emphasis is required on modelling and measuring surface-layer flow over heterogeneous urban canopies.

Keywords

Sodar Source area Surface heterogeneity Urban boundary layer Urban canopy Wind profile 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Bou-Zeid E, Parlange MB (2007) On the parameterization of surface roughness at regional scales. J Atmos Sci 64: 216–227CrossRefGoogle Scholar
  2. Britter RB, Hanna SR (2003) Flow and dispersion in urban areas. Annu Rev Fluid Mech 35: 469–496CrossRefGoogle Scholar
  3. Cheng H, Castro IP (2002) Near-wall flow development after a step change in surface roughness. Boundary-Layer Meteorol 105: 411–432CrossRefGoogle Scholar
  4. Coceal O, Belcher SE (2004) A canopy model of mean winds through urban areas. Quart J Roy Meteorol Soc 130: 1–24CrossRefGoogle Scholar
  5. Coceal O, Belcher SE (2005) Mean winds through an inhomogeneous canopy. Boundary-Layer Meteorol 115: 47–68CrossRefGoogle Scholar
  6. Coulter RL, Pekour MS, Martin TJ (2004) Comparative study of sodar-derived dissipation rates in urban and suburban environments. In: 12th international symposium on acoustic remote sensing, Cambridge, Mass, USAGoogle Scholar
  7. Cullen MJP, Davies T, Mawson MH, James JA, Coulter SC, Malcolm A (1997) An overview of numerical methods for the next generation UK NWP and climate model. In: Lin CA, Laprise R, Ritchie H (eds) Numerical methods in atmospheric and ocean modelling: the Andre J. Robert memorial volume, 1st edn. Canadian Meteorological and Oceanographic Society/NRC Research Press, OttawaGoogle Scholar
  8. Davies F, Collier CG, Pearson GN, Bozier KE (2004) Doppler lidar measurements of turbulent structure function over an urban area. J Atmos Ocean Technol 21: 753–761CrossRefGoogle Scholar
  9. Emeis S, Münkel C, Vogt S, Müller WJ, Schäfer K (2004) Atmospheric boundary-layer structure from simultaneous SODAR, RASS, and ceilometer measurements. Atmos Environ 38: 273–286CrossRefGoogle Scholar
  10. Garratt JR (1990) The internal boundary layer – a review. Boundary-Layer Meteorol 50(1–4): 171–203CrossRefGoogle Scholar
  11. Kaimal JC, Wyngaard JC, Haugen DA, Coté OR (1976) Turbulence structure in the convective boundary layer. J Atmos Sci 33: 2152–2169CrossRefGoogle Scholar
  12. Lumley JL, Panofsky HA (1964) The structure of atmospheric turbulence. Wiley-Interscience, New York, p 239Google Scholar
  13. Mahrt L (2000) Surface heterogeneity and vertical structure of the boundary layer. Boundary-Layer Meteorol 96: 33–62CrossRefGoogle Scholar
  14. Mason PJ (1988) The formation of areally-averaged roughness lengths. Boundary-Layer Meteorol 114: 399–420Google Scholar
  15. Miyake M (1965) Transformation of the atmospheric boundary layer over inhomogeneous surfaces. Science report 5R-6, University of Washington, SeattleGoogle Scholar
  16. Pearson GN, Collier CG (1999) A pulsed coherent CO2 lidar for boundary-layer meteorology. Quart J Roy Meteorol Soc 125(559): 2703–2721Google Scholar
  17. Rooney GG, Longley ID, Barlow JF (2005) Variation of urban momentum roughness length with land use in the upwind source area, as observed in two U.K. cities. Boundary-Layer Meteorol 115(1): 69–84CrossRefGoogle Scholar
  18. Rotach MW, Vogt R, Bernhofer C, Batchvarova E, Christen A, Clappier A, Feddersen B, Gryning S-E, Martucci G, Mayer H, Mitev V, Oke TR, Parlow E, Richner H, Roth M, Roulet Y-A, Ruffieux D, Salmond JA, Schatzmann M, Voogt JA (2005) BUBBLE – an urban boundary layer meteorology project. Theor Appl Climatol 81: 231–261CrossRefGoogle Scholar
  19. Roth M (2000) Review of atmospheric turbulence over cities. Quart J Roy Meteorol Soc 126: 941–990CrossRefGoogle Scholar
  20. Schmid H-P (1994) Source areas for scalars and scalar fluxes. Boundary-Layer Meteorol 67: 293–318CrossRefGoogle Scholar
  21. Schmid H-P (1997) Experimental design for flux measurements: matching scales of observation and fluxes. Agric For Meteorol 87: 179–200CrossRefGoogle Scholar
  22. Schmid H-P, Bünzli B (1995) The influence of surface texture on the effective roughness length. Quart J Roy Meteorol Soc 121(521): 1–21CrossRefGoogle Scholar
  23. Schmid H-P, Cleugh HA, Grimmond CSB, Oke TR (1991) Spatial variability of energy fluxes in suburban terrain. Boundary-Layer Meteorol 54: 249–276CrossRefGoogle Scholar
  24. VDI Guidelines 3783, part 12 (2000) Environmental meteorology: physical modelling of the flow and dispersion processes in the atmospheric boundary layer, Application of wind tunnels, VDI Handbuch Reinhaltung Luft, Band 1b, December 2000, 35 ppGoogle Scholar
  25. Wieringa J (1993) Representative roughness parameters for homogeneous terrain. Boundary-Layer Meteorol 63: 323–363CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  • J. F. Barlow
    • 1
  • G. G. Rooney
    • 2
  • S. von Hünerbein
    • 3
  • S. G. Bradley
    • 4
  1. 1.Department of MeteorologyUniversity of ReadingReadingUK
  2. 2.Met OfficeExeterUK
  3. 3.School of Computing, Science and EngineeringUniversity of SalfordSalfordUK
  4. 4.Department of PhysicsUniversity of AucklandAucklandNew Zealand

Personalised recommendations