User's Guide ______________________________________________________________________
286 _________________________________________________________________ M211296EN-A
Soil Heat Flux (G)
t
TT
dcG
nn
ss
1
where
T
n
=
Temperature on day n [C]
T
n-1
=
Temperature on preceding day n-1 [C]
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 ()
P
PC
p
00163.010
3
where
=
Psychometric constant [kPa C
-1
]
C
p
=
Specific heat of moist air = 1.013 kJ kg
-1
C
-1
P = Atmospheric pressure [kPa]
= Ratio molecular weight water vapor/dry air = 0.622
= Latent heat of vaporization [ML kg
-1
]
is given by the following formula:
T)10361.2(501.2
3
Average Air Temperature (T)
Where hourly data is available:
24
0
24
i
i
T
T
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