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| DOI: | 10.1016/j.agwat.2018.12.014 |
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| Web URL(s): | https://www.sciencedirect.com/science/article/pii/S0378377418312630
Last checked: 04/30/2019
Access conditions: Item is within a limited-access website
https://www.sciencedirect.com/science/article/pii/S0378377418312630/pdfft?md5=80518cc3a83d9b8a5f3a75a19555a644&pid=1-s2.0-S0378377418312630-main.pdf
Last checked: 04/30/2019
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| Publication Type:
| Refereed |
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| Author(s): | Paredes, P.;
Pereira, L. S. |
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| Author Affiliation: | Centro de Investigação em Agronomia, Alimentos, Ambiente e Paisagem (LEAF), Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, Lisboa, Portugal |
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| Title: | Computing FAO56 reference grass evapotranspiration PM-ETo from temperature with focus on solar radiation |
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| Source: | Agricultural Water Management. Vol. 215, April 20 2019, p. 86-102. |
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| Publishing Information: | [Amsterdam]: Elsevier Scientific Pub. |
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| # of Pages: | 17 |
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| Keywords: | TIC Keywords: Evapotranspiration; Humidity; Mathematical equations; Solar radiation
Author-Supplied Keywords: PM-ET0 with reduced datasets (PMT); Dew-point temperature; Default wind speed; Solar radiation; Radiation adjustment coefficient kRs; Predictive equations for kRs
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| Abstract/Contents: | "The computation of the reference crop evapotranspiration (ETo) using the FAO Penman-Monteith equation (PM-ETo) requires data on maximum and minimum air temperatures (Tmax, Tmin), vapour pressure deficit (VPD), solar radiation (Rs) and wind speed at 2m height (u2). However, those data are often not available, or data sets may be incomplete or have questionable quality. Various procedures were proposed in FAO56 to overcome these limitations and an abundant literature has been and is being produced relative to alternative computational methods. Studies applied to a variety of climates, from hyper-arid to humid, have demonstrated that improved methods to compute PM-ETo from temperature only (PMT approach) have appropriate accuracy. These methods refer to estimating: (i) the dew point temperature (Tdew) from Tmin or, in case of humid climates, from the mean temperature, Tmean; (ii) Rs from the temperature difference (TD = Tmax-Tmin); and (iii) u2 using default global or regional values. Greater difficulties refer to the need for locally calibrating the radiation adjustment coefficient (kRs) used with the Rs equation. Therefore, considering that calibrated kRs values were made available by past studies for a large number of locations and diverse climates, the current study developed and tested simple computational approaches relating locally calibrated kRs with various observed weather variables TD, relative humidity (RH) and average u2. The equations were developed using CLIMWAT monthly full-data relative to all the Mediterranean countries. The equations refer to all available data, or to data grouped as hyper-arid and arid, semi-arid, dry and moist sub-humid, and humid climates. To test those kRs equations, ETo computed from temperature and using the predicted kRs values were compared with ETo computed with full data sets of the same Mediterranean locations and of Iran, Inner Mongolia, Portugal and Bolivia. RMSE average values result then small, ranging from 0.34 to 0.54mm day-1, therefore not very far from values obtained when a trial and error procedure was used for all the same locations, from 0.27 to 0.46mm day-1. These indicators allow to propose the use of kRs obtained from the predictive equations instead of locally calibrated kRs values, which greatly eases computations and may largely favour the use of the PMT approach." |
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| Language: | English |
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| References: | 73 |
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| Note: | Flow chart
Maps
Tables
Graphs |
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| ASA/CSSA/SSSA Citation (Crop Science-Like - may be incomplete):
Paredes, P., and L. S. Pereira. 2019. Computing FAO56 reference grass evapotranspiration PM-ETo from temperature with focus on solar radiation. Agric. Water Manage. 215:p. 86-102. |
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| DOI: 10.1016/j.agwat.2018.12.014 |
| Web URL(s):
https://www.sciencedirect.com/science/article/pii/S0378377418312630
Last checked: 04/30/2019
Access conditions: Item is within a limited-access website
https://www.sciencedirect.com/science/article/pii/S0378377418312630/pdfft?md5=80518cc3a83d9b8a5f3a75a19555a644&pid=1-s2.0-S0378377418312630-main.pdf
Last checked: 04/30/2019
Requires: PDF Reader
Access conditions: Item is within a limited-access website |
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