Frost Protection - UTL Repository

MECHANISMS OF ENERGY TRANSFER
TABLE 3.3
Net long-wave radiation (W m -2 ) for a range of air (T a ) and subzero dew-point (T d )
temperatures (°C) and saturation vapour pressure at the dew-point temperature (e d ) in
kPa. The R Ln values were calculated using Equations 3.21 and 3.23, and assuming f =1.0
T a (°C)
DEW-POINT TEMPERATURE (°C)
0 -2 -4 -6
12
10
8
6
4
2
0
-2
-4
-6
-86
-84
-82
-79
-77
-75
-73
-89
-87
-84
-82
-80
-77
-75
-73
-92
-90
-87
-85
-82
-80
-78
-75
-73
-95
-92
-89
-87
-84
-82
-80
-77
-75
-73
e d (kPa) =
0.6108
0.5274
0.4543
0.3902
FIGURE 3.13
Net radiation (R n ), soil heat flux density (G), air temperature (T a ) at 1.5 m, and dewpoint
temperature (T d ) at 1.5 m in a walnut orchard with a partial grass and weed
cover crop in Indian Valley, California, USA (latitude 39°N) on 14–15 March 2001
30
600
sunset
20
400
T a and T d ( ° C)
10
200
R n and G (Wm-2 )
0
0
-10
-200
08.00
10.00
12.00
14.00
16.00
18.00
20.00
22.00
24.00
02.00
04.00
06.00
08.00
P A C I F I C S T A N D A R D T I M E
T T d R n G
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