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In these conditions, the actual evapotranspiration would match the Penman rate of potential evapotranspiration. However, observations revealed that actual evaporation was 1.26 times greater than potential evaporation, and therefore the equation for actual evaporation was found by taking potential evapotranspiration and multiplying it by α ...
In these conditions, the actual evapotranspiration would match the Penman rate of reference evapotranspiration. However, observations revealed that actual evaporation was 1.26 times greater than reference evaporation.
Potential evapotranspiration is expressed in terms of a depth of water or soil moisture percentage. 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 (also called evaporative demand).
The Penman equation describes evaporation (E) from an open water surface, and was developed by Howard Penman in 1948. Penman's equation requires daily mean temperature, wind speed, air pressure, and solar radiation to predict E. Simpler Hydrometeorological equations continue to be used where obtaining such data is impractical, to give comparable results within specific contexts, e.g. humid vs ...
It is a steel container 1.83 m (6 ft) on a side and 0.61 m (2 ft) deep, sunk into the ground with an above-ground rim of 7.6–10 centimetres (3.0–3.9 in) and is painted black internally. Its evaporation rate is lower than the Class A pan and conversion factors must be used. [8]
Potential evapotranspiration (PET), is the evaporation and transpiration that potentially could occur if a field of the crop had an ideal unlimited water supply. RET is the reference ET often denoted as ET 0 .
In 1948, C. W. Thornthwaite proposed an AI defined as: = where the water deficiency is calculated as the sum of the monthly differences between precipitation and potential evapotranspiration for those months when the normal precipitation is less than the normal evapotranspiration; and where stands for the sum of monthly values of potential evapotranspiration for the deficient months (after ...
Third, the actual Evapotranspiration (ETPa) is calculated, first by using an external model (such as Penman-Montieth) for finding the potential ETP and then fitting the result to the temperatures and the permanent wilting point(PWP) of the catchment in question. A parameter C which reflects the increase in the ETP with the differences in ...