Exploring ground-based methods for the validation of remotely sensed evapotranspiration

Accurate estimates of evapotranspiration (ET) are essential when calculating catchment-scale water balances. An open top chamber (OTC), a ground-based method for measuring actual ET, was used to validate modeled ET from earth observation MODIS and agrometeorological data. We studied and compared the...

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Bibliographic Details
Published in:African journal of range & forage science 2015-01, Vol.32 (1), p.41-50
Main Authors: Finca, Andiswa, Palmer, Anthony R, Kakembo, Vincent
Format: Article
Language:English
Subjects:
evapotranspiration
Methods
MODIS LAI
open top chamber
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Summary:Accurate estimates of evapotranspiration (ET) are essential when calculating catchment-scale water balances. An open top chamber (OTC), a ground-based method for measuring actual ET, was used to validate modeled ET from earth observation MODIS and agrometeorological data. We studied and compared the modeled ET (ET MODIS of two adjacent, quaternary catchments from the Bushman's River primary catchment, namely P10A and Q91C, representing light and heavy stocking density, respectively. Within each catchment, a relatively homogenous 1 km 2 pixel of grassland was selected for intensive study. Mean annual ET MODIS results from 2009 to 2011 showed that P10A (light) was higher by 14 mm than Q91C (heavy). No significant difference was observed between hourly ET MODIS and hourly ET OTC . A good relationship was observed between daily ET MODIS and ET OTC (r 2 = 0.7065, p value < 0.01, df = 8) for each 1 km 2 pixel during the 2010/11 growing season. This confirmed that the OTC is a useful instrument to determine actual ET over grassland and short shrubland, and may be used in model validation.
ISSN:1022-0119
1727-9380
DOI:10.2989/10220119.2014.908953