How do you calculate evapotranspiration rate?

Generally what you’ll do is add the highest temperature during a 24-hour period to the lowest temperature during that same period, then divide that sum by 2. This will give you a good estimate for the average temperature during that time.

What is reference crop evapotranspiration?

Reference crop evapotranspiration or reference evapotranspiration, denoted as ETo or ETref, is the estimation of the evapotranspiration from the “reference surface.” The reference surface is a hypothetical grass reference crop with an assumed crop height of 0.12 m, a fixed surface resistance of 70 s/m and an albedo of …

Which method is used for estimation of pet?

The most internationally accepted method for estimating PET is the FAO Penman–Monteith (FAO P-M) formula. It is internationally recognised as the most effective method to estimate PET and has been shown to provide accurate estimations under different conditions (Allen et al. 1998).

Why is evapotranspiration higher in summer?

Potential Evapotranspiration PET is higher in the summer, on less cloudy days, and closer to the equator, because of the higher levels of solar radiation that provides the energy for evaporation.

How do you calculate maximum evapotranspiration?

For the calculation of evapotranspiration, the slope of the relationship between saturation vapor pressure and temperature, о, is required. Tmean = mean daily air temperature, ºC, [Eq. 5] exp = 2.7183 (base of natural logarithm).

What is crop ETo?

CROP COEFFICIENTS Reference crop evapotranspiration (ETo) is an estimate of the water used by a well-watered, full-cover grass surface, 8-15 cm in height (the reference crop). As previously mentioned, a correction factor or crop coefficient (Kc) is required to convert ETo to ET for a specific crop.

What is FAO Penman-Monteith?

The FAO Penman-Monteith method is selected as the method by which the evapotranspiration of this reference surface (ETo) can be unambiguously determined, and as the method which provides consistent ETo values in all regions and climates.

What is FAO Penman-Monteith equation?

The FAO Penman-Monteith equation determines the evapotranspiration from the hypothetical grass reference surface and provides a standard to which evapotranspiration in different periods of the year or in other regions can be compared and to which the evapotranspiration from other crops can be related.

What are four factors affecting evapotranspiration?

The principal weather parameters affecting evapotranspiration are radiation, air temperature, humidity and wind speed.