Knowra Potential evapotranspiration Potential evapotranspiration Potential evapotranspiration (PET) is the estimated rate of water transfer to the atmosphere by evaporation and plant transpiration when water supply does not limit the process. It represents atmospheric demand for water from a surface.
Evapotranspiration : The combined transfer of water from land to the atmosphere through evaporation and plant transpiration. PET estimates the maximum rate of this combined water flux under sufficient supply.
Evaporation : The change of liquid water into vapor at a surface. It is one of the two fluxes included in evapotranspiration estimates.
Crop coefficient : A factor that adjusts reference evapotranspiration to estimate water use by a particular crop and growth stage. Multiplying reference ET by a crop coefficient converts atmospheric demand into crop-specific estimates.
Actual evapotranspiration : The water actually transferred to the atmosphere by evaporation and plant transpiration under prevailing conditions. Unlike PET, it is constrained by available soil water, vegetation, and surface conditions.
Penman–Monteith equation : A physically based equation for estimating evapotranspiration from radiation, temperature, humidity, wind, and surface resistance. It is a widely used method for calculating reference evapotranspiration as an estimate of atmospheric demand.
Transpiration : The movement of water through plants and its release as vapor, mainly through leaf stomata. It is the plant-mediated component of the water transfer estimated by PET.
Irrigation scheduling : Planning when and how much water to apply to crops. PET-based estimates help determine crop water demand between rainfall events.
Pan evaporation : The measured loss of water from an exposed evaporation pan over a period of time. Pan measurements are observations from an artificial surface, not direct estimates of PET.
Reference evapotranspiration : Evapotranspiration from a defined, well-watered reference surface under specified meteorological conditions. It provides a standardized approximation of PET for comparing climates and estimating crop water needs.
Net radiation : The balance of incoming and outgoing shortwave and longwave radiation at a surface. It supplies much of the energy available for evaporation and transpiration.
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