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| | '''Remarks''' | | '''Remarks''' | ||
| |- | |- | ||
| - | | Temperature | + | | '''Temperature''' |
| | Maximum and minimum temperature | | Maximum and minimum temperature | ||
| | Some ET<sub>0</sub> calculation methods use average temperature only. AgrometShell needs both minimum and maximum temperatures. | | Some ET<sub>0</sub> calculation methods use average temperature only. AgrometShell needs both minimum and maximum temperatures. | ||
| |- | |- | ||
| |- | |- | ||
| - | | Radiation (MJ/m<sup>2</sup> | + | | '''Radiation (MJ/m<sup>2</sup>)''' |
| | Global radiation | | Global radiation | ||
| | Global radiation can be calculated from sunshine hours or sunshine fraction accompanied by latitude and day in the year (Julian Date). | | 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 (m/sec)''' |
| | 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. | ||
Revision as of 08:32, 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.
- 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