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Table 2

The names of each component in the Penman–Monteith equation and the formulae used to calculate them

NameFormulaUnits
Saturation vapor pressure/temperature curve  kPa/°C 
Actual water vapor pressure  kPa 
Soil heat flux  MJ/(m2 d) 
Constant of wetting and drying  kPa/°C 
Latent heat of vaporization of water  MJ/kg 
Net radiation from the canopy  MJ/(m2 d) 
Net short-ware radiation  MJ/(m2 d) 
Net long-ware radiation  MJ/(m2 d) 
Theoretical total solar radiation  MJ/(m2 d) 
Sun-earth relative distance   
Sun magnetic declination  rad 
Sunset hour angle  rad 
Theoretical sunshine duration  
NameFormulaUnits
Saturation vapor pressure/temperature curve  kPa/°C 
Actual water vapor pressure  kPa 
Soil heat flux  MJ/(m2 d) 
Constant of wetting and drying  kPa/°C 
Latent heat of vaporization of water  MJ/kg 
Net radiation from the canopy  MJ/(m2 d) 
Net short-ware radiation  MJ/(m2 d) 
Net long-ware radiation  MJ/(m2 d) 
Theoretical total solar radiation  MJ/(m2 d) 
Sun-earth relative distance   
Sun magnetic declination  rad 
Sunset hour angle  rad 
Theoretical sunshine duration  
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