Geoscience Reference
In-Depth Information
Table 26.7(e)
Daily average evaporation from unstressed crops calculated using the
Matt-Shuttleworth approach and the FAO crop factor method for an alfalfa crop, a
cotton crop, and a sugar cane crop calculated at three Australian sites in question 10.
Variable
Units
Site 1
Site 2
Site 3
Average temperature
(
°C
)
23.50
28.20
17.25
Vapor pressure deficit
(kPa)
1.177
2.492
0.770
Modified wind speed
(m s
−1
)
4.19
3.51
3.70
Extraterrestrial solar radiation
(mm day
−1
)
16.61
16.34
15.68
Net radiation
(mm day
−1
)
5.35
6.37
4.20
Assigned site humidity
(none)
Humid
Arid
Humid
Air pressure
(kPa)
101.16
100.78
100.95
Latent heat
(MJ kg
−1
)
2.446
2.434
2.460
Delta
(kPa
°C
−1
)
0.1740
0.2217
0.1243
Psychrometric constant
(kPa
°C
−1
)
0.0672
0.0674
0.0668
Modified psychrometric constant
(kPa
°C
−1
)
0.1600
0.1456
0.1484
Ref. Crop Evap. (FAO)
(mm day
−1
)
5.78
8.62
3.75
r
clim
(s m
−1
)
53
73
76
(
D
50
/
D
2
)
(none)
1.21
1.28
1.19
Alfalfa crop
Crop factor
(none)
0.95
0.95
0.95
R
c
(none)
196
196
196
50
(
r
s
)
(s/m)
127
127
127
c
Re-modified psychrometric constant
(kPa
°C
−1
)
0.2494
0.2210
0.2270
Matt-Shuttleworth estimate
(mm day
−1
)
5.22
8.55
3.39
FAO estimate
(mm day
−1
)
5.49
8.19
3.56
Cotton
Crop factor
(none)
1.18
1.18
1.18
R
c
(none)
162
162
162
50
(
r
s
)
c
(s/m)
60
60
60
Re-modified psychrometric constant
(kPa
°C
−1
)
0.1713
0.1552
0.1584
Matt-Shuttleworth estimate
(mm day
−1
)
7.17
11.36
4.77
FAO estimate
(mm day
−1
)
6.82
10.17
4.42
Sugar Cane
Crop factor
(none)
1.25
1.25
1.25
R
c
50
(none)
124
124
124
(
r
s
)
c
(s/m)
63
63
63
Re-modified psychrometric constant
(kPa
°C
−1
)
0.1673
0.1518
0.1924
Matt-Shuttleworth estimate
(mm day
−1
)
6.87
10.82
5.15
FAO Estimate
(mm day
−1
)
7.22
10.77
4.69
