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| ==2.3. Selection of a reference period. == | ==2.3. Selection of a reference period. == | ||
| ------------------------------------ | ------------------------------------ | ||
| + | {| style="background-color:#F5F5F5; border-collapse:collapse" cellspacing="7" border="1" bordercolorlight="#0000FF" bordercolordark="#0000FF"> | ||
| + | |style="border-style: solid; border-width: 1px"|''Peter Hoefsloot, WMO publications'' | ||
| + | |- | ||
| + | |} | ||
| ===Introduction=== | ===Introduction=== | ||
| + | In order to evaluate crop growth, historical data need to be present for the area under study. In different countries, datasets differ substantially. Some countries have a long record even dating back into the years 1800. Some countries have experienced poverty, war or other disruptions in record taking and keeping and do hardly have any records. WMO (The World Meteorological Organization) has initiated many so-called data rescue projects. These projects aim at gathering (agro)meteorological data and entering them into databases. See an example of one of these projects in South East Asia: http://www.vsamp.com/resume/publications/Page_et_al_2004.pdf | ||
| - | In order to evaluate crop growth, historical data need to be present for the area under study. In different countries, datasets differ substantially. Some countries have a long record even dating back into the years 1800. Some countries have experienced poverty, war or other disruptions in record taking and keeping and do hardly have any records. | + | The reference period should at least reflect the latest 30-year climatological periods defined by WMO (1961-1990 or 1970-2000). If possible the reference period could be extended to the main meteorological instrumented period (1870-2000), although one should be aware of climatological differences in such a long period. |
| - | WMO (The World Meteorological Organization) has initiated many so-called data rescue projects. These projects aim at gathering (agro)meteorological data and entering them into databases. See an example of one of these projects in South East Asia: http://www.vsamp.com/resume/publications/Page_et_al_2004.pdf | + | On data a distinction should be made between data that remain fairly stable between years (more or less constant data) and data that have large variations from year to year (data with yearly fluctuations) |
| - | The reference period should at least reflect the latest 30-year climatological periods defined by WMO (1961-1990 or 1970-2000). The second priority level would be since the main meteorological instrumented period (1870-2000), whereas the third level would be since earliest measurements (about 1750). | + | ===Data that may be considered constant for the reference period.=== |
| - | + | ||
| - | '''Crop data''' | + | |
| * Crops (name, varieties and areas) | * Crops (name, varieties and areas) | ||
| * Cycle lengths | * Cycle lengths | ||
| * Phenological stages | * Phenological stages | ||
| * Crop coefficients. | * Crop coefficients. | ||
| + | * Soil water holding capacity | ||
| * For irrigated crops : bund height. | * For irrigated crops : bund height. | ||
| - | * Yields and possibly production per administrative unit. | ||
| - | ===Soil data=== | + | ===Data that fluctuate strongly from year to year=== |
| - | * Water holding capacity | + | * Yields and production data per administrative unit. |
| - | + | ||
| - | ===Wheather data=== | + | |
| * Rainfall | * Rainfall | ||
| - | * Parameters to calculate the potential evapotranspiration (ET0) or measured potential evapotranspiration. In AgrometShell the potential evaporation can be calculated in various ways. The program has a manual calculation function with which to check whether it is possible to calculate the ET0 with a certain number of input parameters. | + | * Parameters to calculate the potential evapotranspiration (ET<sub>0</sub>). Generally one needs data on: |
| - | + | ** Wind speed, e.g. at 2 or 10 meters above ground level | |
| + | ** Temperatures, e.g. daily minimum, maximum, average.. | ||
| + | ** Humidity, relative humidity or vapour pressure | ||
| + | ** Radiation, e.g. sunshine hours, radiation, day length etc… | ||
| + | The ET<sub>0</sub> can be calculated in many ways. AgrometShell provides a possibility to check whether input data qualify for the calculation of the ET<sub>0</sub>. | ||
| {|"class=prettytable" cellpadding="15" border="1" style="border-collapse:collapse" | {|"class=prettytable" cellpadding="15" border="1" style="border-collapse:collapse" | ||
| - | |width="225"|'''Manual ET0 calculation in AgrometShell with function Tools-Potential ET-Manual'''||[[Image:graph21.jpg|500px|]] | + | |width="225"|ET<sub>0</sub> calculation check in AgrometShell with function ‘’Tools-Potential ET-Manual’’||[[Image:graph21.jpg|500px|]] |
| |} | |} | ||
| - | |||
| ===How to get data for the reference period=== | ===How to get data for the reference period=== | ||
| - | |||
| Data for the reference period can be found at various sources inside and outside the country of region of study. | Data for the reference period can be found at various sources inside and outside the country of region of study. | ||
| - | * Wheather data should ideally come from the National Meteorological Service | + | * Wheather data should generally be provided from the National Meteorological Service. |
| - | * Crop and soil data can usually be fond at the Ministry of Agriculture and/or the agricultural extension services. | + | * Crop and soil data can usually be fond at the Ministry of Agriculture and/or the agricultural extension services or FAO. |
| - | + | ||
| - | + | ||
| - | + | ||
| - | + | ||
| </blockquote> | </blockquote> | ||
Revision as of 11:18, 27 September 2006
2.3. Selection of a reference period.
Peter Hoefsloot, WMO publications Introduction
In order to evaluate crop growth, historical data need to be present for the area under study. In different countries, datasets differ substantially. Some countries have a long record even dating back into the years 1800. Some countries have experienced poverty, war or other disruptions in record taking and keeping and do hardly have any records. WMO (The World Meteorological Organization) has initiated many so-called data rescue projects. These projects aim at gathering (agro)meteorological data and entering them into databases. See an example of one of these projects in South East Asia: http://www.vsamp.com/resume/publications/Page_et_al_2004.pdf
The reference period should at least reflect the latest 30-year climatological periods defined by WMO (1961-1990 or 1970-2000). If possible the reference period could be extended to the main meteorological instrumented period (1870-2000), although one should be aware of climatological differences in such a long period.
On data a distinction should be made between data that remain fairly stable between years (more or less constant data) and data that have large variations from year to year (data with yearly fluctuations)
Data that may be considered constant for the reference period.
- Crops (name, varieties and areas)
- Cycle lengths
- Phenological stages
- Crop coefficients.
- Soil water holding capacity
- For irrigated crops : bund height.
Data that fluctuate strongly from year to year
- Yields and production data per administrative unit.
- Rainfall
- Parameters to calculate the potential evapotranspiration (ET0). Generally one needs data on:
- Wind speed, e.g. at 2 or 10 meters above ground level
- Temperatures, e.g. daily minimum, maximum, average..
- Humidity, relative humidity or vapour pressure
- Radiation, e.g. sunshine hours, radiation, day length etc…
The ET0 can be calculated in many ways. AgrometShell provides a possibility to check whether input data qualify for the calculation of the ET0.
ET0 calculation check in AgrometShell with function ‘’Tools-Potential ET-Manual’’ 
How to get data for the reference period
Data for the reference period can be found at various sources inside and outside the country of region of study.
- Wheather data should generally be provided from the National Meteorological Service.
- Crop and soil data can usually be fond at the Ministry of Agriculture and/or the agricultural extension services or FAO.
