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.

Introduction

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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Notes

Glossary

Notation and Abbreviations

b

Building breadth

C

Measured/calculated concentration

CD

Drag coefficient

c+

Normalized mean concentration for a line source

d

Gap or separation distance between buildings

f

Coriolis frequency

F

Froude number

Fv

Surface water vapor flux

Fθ

Fθ

g

Gravitational acceleration

h

Boundary layer height

H

Building height

Hc

Canopy height

Hc

Standard deviation of canopy height, Hc

HM

Mountain height

K

Normalized mean concentration for a point source

k-ε

Kinetic energy and energy-dissipation model of turbulence

l

Vertical length scale of internal layer

lO, lN

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

LA

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

L

Building length

Lf

Coriolis advection length

LI

Inner city length scale

LM, LN, LBS

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

LO

Overall city length scale

LRo

Rossby length scale

LSe

Effective source size

N

Buoyancy frequency

q

Hit rate test score

Q

Emission rate

RD

Fractional deviation

RM

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

s

Distance to the nearest building

\( {u_*} \)

Friction velocity of the turbulent velocity profile of the atmosphere

U

Mean velocity, with subscripts denoting location/physical process

UB

Typical wind speed associated with local buoyancy effects

UC

Wind speed within the canopy

UG

Geostrophic wind

UH

Mean wind above the buildings (at height H)

Uref

Reference velocity

Uc

Mean wind along the street canyon

VS

Mean wind along street

w

Building length or width

W

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

yc(x)

Streamline through source at xs, ys, zs

z0(x, y)

Roughness length for wind profile

zd

Displacement height for logarithmic wind profile

zS(x, y)

Surface elevation of the ground

Zs

Source height

Z*

Height of top of shear layer above buildings

β

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

θ

Mean temperature

θs

Surface temperature

κ

Von Karman’s constant

λp

Planar area index

λf

Frontal area index

σu, σv, σw

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

φ

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

Subscripts

B

Buoyancy

BS

Building/Street scale

c

Canopy

C

Cloud concentration

f

Coriolis

G

Geostrophic

H

At top of buildings/canyon

M

Mesoscale

N

Neighborhood scale

O

Overall urban area

Ro

Rossby

s

Surface, street

S

Source

Se

Effective source

*

Turbulence-related level for log profile, or turbulent source

Abbreviations

BS

Building/street sub-region

CFD

Computational fluid dynamics

FAM

Fast approximate model

FCM

Fully computational model

LES

Large eddy simulation

M

Mesoscale region

N

Neighborhood sub-region

RANS

Reynolds averaged Navier–Stokes

RSM

Reynolds stress model

r.m.s

Root mean square

SVF

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