Evapotranspiration

Evapotranspiration

The displayed evapotranspiration value is calculated using the FAO recommended Penman-Monteith equation.

Documentation

Parameters used

• average daily air temperature
• average daily relative humidity
• average daily atmospheric pressure
• average daily solar radiation
• average daily wind speed and height of measurement
• location elevation
• latitude
• day of the year

Parameters calculated to obtain evapotranspiration value

• slope of saturation vapor pressure curve
• mean saturation vapor pressure
• actual vapor pressure derived from humidity data
• vapor pressure deficit
• inverse relative distance Earth-Sun
• solar declination
• sunset hour angle
• extraterrestrial radiation
• daylight hours
• clear-sky solar radiation
• net solar shortwave radiation
• net longwave radiation
• net radiation

Detailed analysis

Units

	C F			km/h m/s mph kt
	mm in			hPa mmHg inHg
	m ft			m km mi

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