Vaisala AWS330 User Manual
Page 288
User's Guide ______________________________________________________________________
286 _________________________________________________________________ M211296EN-B
Soil Heat Flux (G)
Δ
−
=
−
t
T
T
d
c
G
n
n
s
s
1
where
T
n
=
Temperature on day n [
°
C]
T
n-1
=
Temperature on preceding day n-1 [
°
C]
Δ
t
= Time period [days]
c
s
=
Volumetric heat capacity [MJ m
-3
°
C
-1
] (2.1 for average
moist soil is used)
d
s
= Estimated effective soil depth [m] (0.2 m is used)
Psychometric Constant (
γ
)
λ
ελ
γ
P
P
C
p
00163
.
0
10
3
=
⋅
=
−
where
γ
= Psychometric constant [kPa
°
C
-1
]
C
p
=
Specific heat of moist air = 1.013 kJ kg
-1
°
C
-1
P
= Atmospheric pressure [kPa]
ε
= Ratio molecular weight water vapor/dry air = 0.622
λ
= Latent heat of vaporization [ML kg
-1
]
λ
is given by the following formula:
T
)
10
361
.
2
(
501
.
2
3
−
⋅
−
=
λ
Average Air Temperature (T)
Where hourly data is available:
=
=
24
0
24
i
i
T
T