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dH
2
SO
4
½
=
dt
dSO
4
½
=
dt ¼ WSO
2
½
where W = 0.1 % day
−
1
in the daytime and 0.01 % day
−
1
at night.
Numerous models have been created to simulate the process of sedimentation of
pollutants. So, for instance, Sinik et al. (1985) proposed several parameterizations
for the coef
cient of aerosol washing out from the atmosphere:
r ¼
C
1
dC
dt
r ¼ 10
4
I
1
=
2
r ¼
h
I
a
3
10
4
I
0
:
9
;
;
;
r ¼ 3
:
;
where I = RR/(24 N) is the rain rate (mm/h), RR is the precipitation amount per
month (mm), N is the number of days precipitation,
ʸ
and a are parameters.
The following diffusion equation is widely used
@
@k
V
k
C
@
@
V
h
C
ð
5
@
C
@
t
þ
V
u
@
C
@u
þ
V
k
@
C
@k
þ
V
h
@
C
@
h
¼
@
V
u
C
:
4
Þ
@u
h
If we suppose th
at in
Eq. (
5.4
) an advection prevails over diffusion in the
direction h, that is,
V
h
C
@
V
h
@
@
h
C
=@
h, then Eq. (
5.4
) with respect to
ʻ
gives:
Z
1
@
C
u
@
t
þ
V
h
@
C
u
h
þ
V
k
@
C
u
¼
@
@k
V
k
Cd
u;
@
@k
1
where
Z
1
C
u
¼
Cd
u:
1
As a result of this transformation, the problem becomes two-dimensional.
Chobadian et al. (1985) proposed two formulas to estimate the depth of the
mixed atmospheric layer, which is important in determination of the model
'
s ver-
tical structure:
1
=
2
U
U
a
x
1
h
1
h
2
j
j
8x
1
U
1
a
H ¼ 8
:
Dh;
H ¼
;
j
Dh=D
x
3
j
where x
1
is the rate of shifting with respect to land surface (m s
−
1
),
ʔʸ
is the vertical
gradient of potential temperature in the inverse layer (
°
C), U
*
is the rate of friction
over the leeward surface,
ʸ
1
is the lower level of potential temperature over the
°
ʔʸ
ʔ
source of the pollution (
K), |
/
x
3
| is the absolute value of the rate of motion over
the source.
The desire to simplify the parameterization of individual sub-processes of the
atmospheric pollution dynamics, led in many cases to the development of suffi-
-
ciently simple and efficient models, requiring a small database. Numerous studies
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