d
Gap or separation distance
between buildings
f
Coriolis frequency
F
Froude number
F v
Surface water vapor flux
F θ
F θ
g
Gravitational acceleration
h
Boundary layer height
H
Building height
H c
Canopy height
H c
0
Standard deviation of canopy
height, H c
H M
Mountain height
K
Normalized mean concentration
for a point source
k-ε
Kinetic energy and energydissipation model of turbulence
l
Vertical length scale of internal
layer
l O , l N
Vertical length scales of internal
layers over the urban area,
neighborhood scale
L a
Adjustment length for mean flow
to adjust as it enters the porous
canopy
L
Building length
Lf
Coriolis advection length
L I
Inner city length scale
L M , L N , L BS Length scales of the (sub-)
regions M, N, BS
L O
Overall city length scale
L Ro
Rossby length scale
L Se
Effective source size
N
Buoyancy frequency
q
Hit rate test score
Q
Emission rate
RD
Fractional deviation
R M
Ratio of the length of the
sub-regionL M to the smallest
scales resolved in that region
s
Distance to the nearest building
u
Ã
Friction velocity of the turbulent
velocity profile of the atmosphere
U
Mean velocity, with subscripts
denoting location/physical process
U B
Typical wind speed associated
with local buoyancy effects
U C
Wind speed within the canopy
U G
Geostrophic wind
U H
Mean wind above the buildings
(at height H)
U ref
Reference velocity
U c
Mean wind along the street
canyon
V S
Mean wind along street
w
Building length or width
W
Absolute deviation, Building
width
x 5 (x, y, z) Coordinates of a point
x B
(i) , y B
(i)
Coordinates of staggered building i
x s , y s , z s
Coordinates of source
y c (x)
Streamline through source
at x s , y s , z s
z 0 (x, y)
Roughness length for wind
profile
z d
Displacement height for
logarithmic wind profile
z S (x, y)
Surface elevation of the ground
Z s
Source height
Z Ã
Height of top of shear layer above
buildings
β
“Porosity” of an urban canopy
[β ~ bw/d
2 ]
θ
Mean temperature
θ s
Surface temperature
k
Von Karman’s constant
l p
Planar area index
l f
Frontal area index
s u , s v , s w
R.m.s velocity components (of the
order of u
à )
f
Angle between wind direction and
normal direction to a street (Figs. 3
and 6), i.e., f ¼ 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
188
Urban Air Quality: Meteorological Processes
Gap or separation distance
between buildings
f
Coriolis frequency
F
Froude number
F v
Surface water vapor flux
F θ
F θ
g
Gravitational acceleration
h
Boundary layer height
H
Building height
H c
Canopy height
H c
0
Standard deviation of canopy
height, H c
H M
Mountain height
K
Normalized mean concentration
for a point source
k-ε
Kinetic energy and energydissipation model of turbulence
l
Vertical length scale of internal
layer
l O , l N
Vertical length scales of internal
layers over the urban area,
neighborhood scale
L a
Adjustment length for mean flow
to adjust as it enters the porous
canopy
L
Building length
Lf
Coriolis advection length
L I
Inner city length scale
L M , L N , L BS Length scales of the (sub-)
regions M, N, BS
L O
Overall city length scale
L Ro
Rossby length scale
L Se
Effective source size
N
Buoyancy frequency
q
Hit rate test score
Q
Emission rate
RD
Fractional deviation
R M
Ratio of the length of the
sub-regionL M to the smallest
scales resolved in that region
s
Distance to the nearest building
u
Ã
Friction velocity of the turbulent
velocity profile of the atmosphere
U
Mean velocity, with subscripts
denoting location/physical process
U B
Typical wind speed associated
with local buoyancy effects
U C
Wind speed within the canopy
U G
Geostrophic wind
U H
Mean wind above the buildings
(at height H)
U ref
Reference velocity
U c
Mean wind along the street
canyon
V S
Mean wind along street
w
Building length or width
W
Absolute deviation, Building
width
x 5 (x, y, z) Coordinates of a point
x B
(i) , y B
(i)
Coordinates of staggered building i
x s , y s , z s
Coordinates of source
y c (x)
Streamline through source
at x s , y s , z s
z 0 (x, y)
Roughness length for wind
profile
z d
Displacement height for
logarithmic wind profile
z S (x, y)
Surface elevation of the ground
Z s
Source height
Z Ã
Height of top of shear layer above
buildings
β
“Porosity” of an urban canopy
[β ~ bw/d
2 ]
θ
Mean temperature
θ s
Surface temperature
k
Von Karman’s constant
l p
Planar area index
l f
Frontal area index
s u , s v , s w
R.m.s velocity components (of the
order of u
à )
f
Angle between wind direction and
normal direction to a street (Figs. 3
and 6), i.e., f ¼ 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
188
Urban Air Quality: Meteorological Processes