A New Method to Estimate Reference Crop Evapotranspiration from Geostationary Satellite Imagery: Practical Considerations

Reference crop evapotranspiration (ETo) plays a role in irrigation advisory being of crucial importance for water managers dealing with scarce water resources. Following the ETo definition, it can be shown that total solar radiation is the main driver, allowing ETo estimates from satellite observati...

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Bibliographic Details
Published in:Water (Basel) 2019-02, Vol.11 (2), p.382
Main Authors: de Bruin, Henk, Trigo, Isabel
Format: Article
Language:English
Subjects:
Advection
Aquatic resources
Artificial satellites
Atmospheric boundary layer
Energy
Evapotranspiration
Grasses
Heat
Humidity
Irrigation
Marshall Islands
Methods
Radiation
Remote sensing
Satellite imagery
Sensors
Solar radiation
Spain
Synchronous satellites
Water management
Water resources
Water scarcity
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Summary:Reference crop evapotranspiration (ETo) plays a role in irrigation advisory being of crucial importance for water managers dealing with scarce water resources. Following the ETo definition, it can be shown that total solar radiation is the main driver, allowing ETo estimates from satellite observations. As such, the EUMETSAT LSA-SAF operationally provides ETo primarily derived from the European geostationary satellite MSG. ETo estimations following the original FAO report require several meteorological observations gathered over actual well-watered grass. Here we will consider the impact of two effects on ETo using the LSA-SAF and FAO methodologies: (i) local advection, related to the impact of advection of surrounding warm dry air onto the reference non-water stressed surface; and (ii) the so-called surface aridity error, which occurs when calculating ETo according to FAO, but with input data not collected over well-watered grass. The LSA-SAF ETo is not sensitive to any of these effects. However, it is shown that local advection may increase evapotranspiration over a limited field by up to 30%, while ignoring aridity effects leads to a great overestimation. The practical application of satellite estimates of ETo provided by the LSA-SAF are discussed here, and, furthermore, water managers are encouraged to consider its advantages and ways for improvement.
ISSN:2073-4441
2073-4441
DOI:10.3390/w11020382