Geoscience Reference
In-Depth Information
where f is the Coriolis parameter,
ʓ
is the rate of dry adiabatic deposition, T is the
air temperature,
К
M
and
К
H
are coef
cients of diffusion, u
g
and v
g
are the thermal
wind components:
d
n;
d
g:
Z
Z
Z
Z
gT
f
T
2
@
1
T
ð
t
;
x
;
y
; nÞ
gT
f
T
2
@
1
T
ð
t
;
x
;
y
; gÞ
u
g
¼
v
g
¼
ð
5
:
10
Þ
@
y
@
x
0
0
For practical application of Eqs. (
5.6
)
(
5.10
), the following should be taken into
-
account: deviation and rising of the
flux over the hills, thermal friction, tunneling
effect in valleys, thermal impacts of islands, lakes, and mountains. Additions to the
given system of equations are made proceeding from an actual con
fl
guration and
topology of the region.
The Gauss-type models are used, as a rule, to parameterize the processes of
pollutants
'
propagation near high sources. The best studied modi
cations of the
PGT dispersion model (Pasquill
Gifford
Turner) adequately describes the surface
-
-
fl
fluxes formed from the highly located
sources. Raaschou-Nielsen et al. (2000) have modi
fluxes of pollutants and less accurately the
fl
ed the PGT model providing it
with more universal functions for an arbitrary point source. The modi
cation is
based on the base Gauss-type model to describe the concentration of pollutants in
the surface layer of the atmosphere:
"
#
exp
0
"
#
2
2
Q
h
ef
r
z
k
r
k
C
ðu; k;
0
Þ
¼
exp
0
:
5
:
5
þ
reflection terms
p
u
r
z
r
k
ð
5
:
11
Þ
where Q is the source power, h
ef
is the average height of the pollutants cloud, u is
the effective rate of transport.
Important parameters of the model (
5.11
) are parameters of the pollutant jet
scattering. They are complex functions of the meteorological situations. Theoretical
and observational studies of many authors have shown that the turbulence and
diffusion in the convective boundary layer are controlled by two important
parameters: the height of mixing zi
i
and the scale of convection rate w
*
:
1
=
3
g
T
q
c
p
Yz
i
w
¼
ð
5
:
12
Þ
'
where Y is the surface sensible heat
fl
flux, g is the acceleration of the Earth
is gravity,
T is the air temperature, c
p
is the air speci
c heat at a constant pressure.
The vertical
˃
w
and horizontal
˃
v
constituents of the rate of deviation of the
turbulent
fl
flux from the centre of the convective cloud are proportional to w
*
and,
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