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| | Wind speed at 2 meters | | Wind speed at 2 meters | ||
| | Formulas are available to convert wind speed for other heights (e.g. 10 meters) into a 2 meter value. | | Formulas are available to convert wind speed for other heights (e.g. 10 meters) into a 2 meter value. | ||
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| + | | '''Optional: relative humidity (%)''' | ||
| + | | Maximum and minimum relative humidity during the day. | ||
| + | | Although this parameter is not essential it improves the ET<sub>0</sub> calculations substantially. | ||
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| - | * Temperatures : minimum and maximum in degrees celcius | ||
| - | * Radiation. Radiation can be calculated quite accurately from the number of sunshine hours (or sunshine fraction) accompanied by Day number in the year | ||
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Revision as of 08:34, 4 August 2006
Chapter 11. Development of ET0 computation procedure.
Potential evapotranspiration (ET0) is a vital input to Water Balance calculations, which in turn are a vital part in Crop forecasting. The parameters needed to calculate ET0 are the following:
Parameter group Parameters Remarks Temperature Maximum and minimum temperature Some ET0 calculation methods use average temperature only. AgrometShell needs both minimum and maximum temperatures. Radiation (MJ/m2) Global radiation Global radiation can be calculated from sunshine hours or sunshine fraction accompanied by latitude and day in the year (Julian Date). Wind Speed (m/sec) Wind speed at 2 meters Formulas are available to convert wind speed for other heights (e.g. 10 meters) into a 2 meter value. Optional: relative humidity (%) Maximum and minimum relative humidity during the day. Although this parameter is not essential it improves the ET0 calculations substantially.