Encyclopedia of Sustainability Science and Technology

2012 Edition
| Editors: Robert A. Meyers

Urban Air Quality: Meteorological Processes

  • David Carruthers
  • Silvana Di Sabatino
  • Julian Hunt
Reference work entry
DOI: https://doi.org/10.1007/978-1-4419-0851-3_427

Definition of the Subject

Meteorological processes in urban areas that are relevant to urban air quality. Of most significance are the impacts of the urban morphology on the mean flow and turbulence, which determines the transport and dispersion of pollutants and therefore their concentration.


Concentrations of pollutants within an urban area depend on a number of different factors. These include the emissions of pollutants within the urban area, pollutant concentrations transported into the area, and the meteorology within the urban area, in particular, the mean airflow and turbulence (which determines the movement and mixing of the emitted pollutants) and the temperature and solar insolation (which impacts on chemical transformation taking place). This entry discusses meteorology within the urban area with the focus being on the mean flow and turbulence, as these may be substantially different from the upstream flow. Discussed here are the current understanding,...

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Notation and Abbreviations


Building breadth


Measured/calculated concentration


Drag coefficient


Normalized mean concentration for a line source


Gap or separation distance between buildings


Coriolis frequency


Froude number


Surface water vapor flux




Gravitational acceleration


Boundary layer height


Building height


Canopy height


Standard deviation of canopy height, Hc


Mountain height


Normalized mean concentration for a point source


Kinetic energy and energy-dissipation model of turbulence


Vertical length scale of internal layer

lO, lN

Vertical length scales of internal layers over the urban area, neighborhood scale


Adjustment length for mean flow to adjust as it enters the porous canopy


Building length


Coriolis advection length


Inner city length scale


Length scales of the (sub-)regions M, N, BS


Overall city length scale


Rossby length scale


Effective source size


Buoyancy frequency


Hit rate test score


Emission rate


Fractional deviation


Ratio of the length of the sub-regionL M to the smallest scales resolved in that region


Distance to the nearest building

\( {u_*} \)

Friction velocity of the turbulent velocity profile of the atmosphere


Mean velocity, with subscripts denoting location/physical process


Typical wind speed associated with local buoyancy effects


Wind speed within the canopy


Geostrophic wind


Mean wind above the buildings (at height H)


Reference velocity


Mean wind along the street canyon


Mean wind along street


Building length or width


Absolute deviation, Building width

x= (x, y, z)

Coordinates of a point

xB(i), yB(i)

Coordinates of staggered building i

xs, ys, zs

Coordinates of source


Streamline through source at xs, ys, zs

z0(x, y)

Roughness length for wind profile


Displacement height for logarithmic wind profile

zS(x, y)

Surface elevation of the ground


Source height


Height of top of shear layer above buildings


“Porosity” of an urban canopy [β ∼ bw/d2]


Mean temperature


Surface temperature


Von Karman’s constant


Planar area index


Frontal area index

σu, σv, σw

R.m.s velocity components (of the order of \( {u_*} \))


Angle between wind direction and normal direction to a street (Figs. 3 and 6), i.e., φ = 90° if wind is along the street.





Building/Street scale




Cloud concentration






At top of buildings/canyon




Neighborhood scale


Overall urban area




Surface, street




Effective source


Turbulence-related level for log profile, or turbulent source



Building/street sub-region


Computational fluid dynamics


Fast approximate model


Fully computational model


Large eddy simulation


Mesoscale region


Neighborhood sub-region


Reynolds averaged Navier–Stokes


Reynolds stress model


Root mean square


Sky view factor


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Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  • David Carruthers
    • 1
  • Silvana Di Sabatino
    • 2
  • Julian Hunt
    • 3
  1. 1.Cambridge Environmental Research ConsultantsCambridgeUK
  2. 2.Dipartimento di Scienza dei MaterialiUniversità del SalentoLecceItaly
  3. 3.University College LondonLondonUK