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T = 20oC
Qn = 620 cal/cm2/d
v2 = 200 km/d
RH = 75%
The saturation vapor pressure at the overlying air temperature of 20oC is:
eo = 23.37 mb
For the given climatic conditions,
the mass-transfer evaporation rate according to Dunne is:
Ea = (0.013 + 0.00016 × 200) × 23.37 × [(100 - 75)/100] = 0.263 cm/d
The evaporation rate due to net radiation is:
En = (620 cal/cm2/d) / (0.998 gr/cm3 × 586 cal/gr) = 1.06 cm/d
Penman's ratio (Table 2-4):
α = 2.19
The evaporation rate by the Penman formula is:
E = (2.19 × 1.06 + 0.263) / (2.19 + 1) = 0.81 cm/d. ANSWER.
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