Potential evaporation

Potential evaporation or potential evapotranspiration (PET) is defined as the amount of evaporation that would occur if a sufficient water source were available. If the actual evapotranspiration is considered the net result of atmospheric demand for moisture from a surface and the ability of the surface to supply moisture, then PET is a measure of the demand side. Surface and air temperatures, insolation, and wind all affect this. A dryland is a place where annual potential evaporation exceeds annual precipitation.

${\displaystyle PET=16\left({\frac {L}{12}}\right)\left({\frac {N}{30}}\right)\left({\frac {10\,T_{a}}{I}}\right)^{\alpha }}$

Where

${\displaystyle PET}$ is the estimated potential evaporation (mm/month)

${\displaystyle T_{a}}$ is the average daily temperature (degrees Celsius; if this is negative, use ${\displaystyle 0}$) of the month being calculated

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