Abstract
ABSTRACT The estimate of the actual surface evapotranspiration (ET) contributes to quantifying the water needs of crops. An alternative to the use of lysimeter for an accurate estimation of water needs, which has proved to be of great value in recent years, is the use of remote sensing combined with models based on surface energy balance. There is wide variety of models that can be classified into two types: one-source models, such as the Mapping EvapoTranspiration at high Resolution with Internalized Calibration (METRIC) algorithm, or two-source models, such as the Simplified Two-Source Energy Balance (STSEB). The objective of this study was to analyze how METRIC and STSEB can be used to estimate ET, in comparison with the lysimeter data, for the different stages of development of the sorghum crop in Apodi, RN, Brazil. The accuracy of both models in the daily ET estimation for the semi-arid conditions of the experiment, with RMSE values of 0.8 and of 0.7 mm d-1 through METRIC and STSEB, respectively, is considered acceptable for irrigation management purposes. The errors obtained with METRIC at an instantaneous scale were 60, 50, 130 and 5 W m-2 for Rn, LE, H and G, respectively, on the other hand, using STSEB these errors were of 40, 70, 120 and 21 W m-2 for Rn, LE, H and G, respectively. The METRIC and STSEB models are very similar when it comes to providing information on water needs of the sorghum.
Highlights
There has been an increasing number of irrigated areas in Northeastern Brazil, a region characterized by problems caused by water scarcity
An accurate estimation of actual evapotranspiration (ET) makes it possible to replace a quantity of water closer to the actual needs, being a key indicative in irrigation management, and can be determined using remote sensing techniques and from models based on the surface energy balance
This study aimed to evaluate the METRIC and Simplified Two-Source Energy Balance (STSEB) models, comparing the data measured in the field of the sorghum crop, as well as to monitor the water needs of this crop during its growth cycle
Summary
There has been an increasing number of irrigated areas in Northeastern Brazil, a region characterized by problems caused by water scarcity. In this regard, it is evident that most of these areas require adequate irrigation management, which can be accomplished by estimating the water needs of crops in the different stages of their phenological cycle. Energy balance models can be classified into two types: one-source models (Oliveira et al, 2014; Paço et al, 2014; González-Piqueras et al, 2015; Madugundu et al, 2017) or two-source models (Sánchez et al, 2011; González-Dugo et al, 2012; Sánchez et al, 2014) These models are based on the surface energy balance through the determination of the latent heat flux (LE), estimating net radiation (Rn), sensible heat flux (H) and soil heat flux (G) (González-Piqueras et al, 2015). The Simplified Two-Source Energy Balance (STSEB) model is a two-source model, considered of solid physical basis as it requires precise input data from both ground agrometeorological stations and remote platforms (under atmospheric corrections in the visible and near-infrared range and of emissivity in thermal infrared)
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