(Difference between revisions)
| Revision as of 08:34, 4 August 2006 Peter (Talk | contribs) (→'''Chapter 11. Development of ET<sub>0</sub> computation procedure.''') ← Previous diff |
Revision as of 08:39, 4 August 2006 Peter (Talk | contribs) (→'''Chapter 11. Development of ET<sub>0</sub> computation procedure.''') Next diff → |
||
| Line 26: | Line 26: | ||
| | '''Optional: relative humidity (%)''' | | '''Optional: relative humidity (%)''' | ||
| | Maximum and minimum relative humidity during the day. | | Maximum and minimum relative humidity during the day. | ||
| - | | Although this parameter is not essential it improves the ET<sub>0</sub> calculations substantially. | + | | Although this parameter is not essential it improves the ET<sub>0</sub> calculations substantially. In AgrometShell relative humidity can be calculated from vapour pressure measurements. |
| |- | |- | ||
| |} | |} | ||
Revision as of 08:39, 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. In AgrometShell relative humidity can be calculated from vapour pressure measurements.