Agriculture Reference
In-Depth Information
temperature, atmospheric water vapor pressure deficit and water stress [35] is parameterized
as
1
.
1
F
f
1
+
[
]
r
R
LAI
{
[
()
]
}
−
1
(
)
2
−
1
−
1
s
min
ol
r
=
1
.
0
−
0
.
0016
298
−
T
1
−
η
e
T
−
e
Ф
(36)
c
r
*
f
r
2
LAI
1
.
1
F
r
f
s
min
+
R
LAI
r
ol
s
max
where
r
s min
,
r
s max
are the minimum and maximum of stomatal resistance (s m
-1
);
R
0l
is limit
value of 100 W m
-2
for crops; and
η
the crop-dependent empirical parameter that is equal to
0.025 hPa
-1
. In this model the value of 5000 s m
-1
for
r
s max
is used. The factor
Ф
2
takes into
account the effect of water stress on the stomatal resistance and is parameterized in the
following way
⎧
1
ϑ
>
ϑ
a
fc
⎪
⎨
(37)
1
⎪
⎛
⎞
ϑ
wil
Ф
=
1
−
⎜
⎝
⎟
⎠
ϑ
≤
ϑ
≤
ϑ
2
wil
a
fc
⎪
⎩
ϑ
a
⎪
0
ϑ
<
ϑ
a
wil
where ϑ
a
is the mean volumetric soil water content in the first and second soil layers (m
3
m
-3
);
ϑ
wil
is volumetric soil water content at wilting point (m
3
m
-3
); and ϑ
fc
volumetric soil water
content at field capacity (m
3
m
-3
).
The soil surface resistance,
r
surf
, is parameterized using the empirical expression given by
Sun (1982) [41], i.e.,
(38)
−
d
r
=
d
+
d
ϑ
surf
1
2
1
where
d
1
,
d
2
(s m
-1
) and
d
3
are empirical constants [42], while ϑ
1
is the top volumetric soil
water content (m
3
m
-3
).
2.5. Hydrological Module
The parameterization of the volumetric soil moisture content is based on the following
three governing equations
⎡
E
+
E
⎤
∂
ϑ
1
=
P
−
F
−
g
tf
,
−
R
−
R
(39)
1
⎣
⎦
1
1
2
0
1
∂
t
D
ρ
1
w
E
∂
ϑ
⎡
⎤
1
tf
ρ
,
2
=
F
−
F
−
−
R
(40)
2
⎣
⎦
1
2
2
,
3
2
∂
t
D
2
w
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