height (C), u2 is wind speed at 2 m height (m s
1),
es ea is saturation vapor pressure deficit (kPa), D is the
slope of the vapor pressure curve (kPa C
1), and g is the
psychrometric constant (kPa C
1).
[21] ETref as described in equation (
3) is the potential
evapotranspiration for a hypothetical grass reference crop
with an assumed crop height of 0.12 m, a fixed surface
resistance of 70 s m
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