Operator`s manual

63
Manual
in which:
E = evaporation rate [M day
-1
]
v
= is Latent Heat of Vaporization [J g
-1
]
w
= mass density of water [g m
-3
]
= gradient of the saturated vapor pressure versus temperature [kPa °C
-1
]
y = psychrometric constant [kPa °C
-1
]
R
n
= net solar radiation [J M
-2
day
-1
]
ES = change in energy storage [J M
-2
Day
-1
]
Net Solar Radiation R
n
R
n
= R
net-short-wave
+ R
net-long-wave
Using the formulas and box-calculations described in the previous text, it follows that:
R
net-short-wave
= R
short-wave-in
x (1 – a)
R
net-short-wave
= 22.8 x 10
6
x (1 – 0.08) = 21.0 x 10
6
[J M
-2
day
-1
]
The net long wave radiation was calculated in BOX 3, and resulted in:
R
net-long-wave
= 7.73 x 10
6
[J M
-2
day
-1
]
Hence,
R
n
= 21.0 x 10
6
– 7.73 x 10
6
= 13.27 x 10
6
[J M
-2
day
-1
]
Gradient of Saturated Vapor Pressure versus Temperature
Using the results from BOX2, it follows that:
= 0.145 [kPa °C
-1
]
Psychrometric Constant y
y = 0.066 [kPa °C
-1
]
Mass Density of Water w
w
= 0.99836 x 10
6
[g m
-3
]
Latent Heat of Vaporization
v
Using the results from BOX1, it follows that:
v
= 2450 [J g
-1
]
Change in Energy Storage ES
The change in energy storage was calculated in BOX 4, and resulted in:
ES = 3.13 x 10
6
[J M
-2
Day
-1
]
Annexes