SENSITIVITY OF EVAPOTRANSPIRATION ESTIMATED BY ORBITAL IMAGES UNDER INFLUENCE OF SURFACE TEMPERATURE

Roberto Filgueiras,Fernando F Da Cunha,Everardo C Mantovani,Santos H B Dias,Daniel Althoff

doi:10.1590/1809-4430-eng.agric.v39nep23-32/2019

Roberto Filgueiras, Fernando F Da Cunha + Show 3 more

Open Access

https://doi.org/10.1590/1809-4430-eng.agric.v39nep23-32/2019

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Abstract

Surface temperature (Ts) is a determining factor to obtain energy balance parameters, being relevant to understand the influence of this variable on the estimation of evapotranspiration. Thus, the objective of this study was to simulate errors in Ts estimation to verify the consequences of actual evapotranspiration (ETa) estimated by the SAFER (Simple Algorithm for Evapotranspiration Retrieving) model. For this, an image of the Landsat-8 satellite was used to induce errors from 0.2K to 10K in the variable Ts, allowing verifying the consequences in the ETa data. After the estimations of Ts and ETa, the quantitative consequences and dynamics of Ts impact on the ETa data were verified along the different land uses in the study area. The results showed that the precise estimation of Ts is essential to obtain ETa accurately. The image of ETa errors presented the highest relative errors on the surface with exposed soils and with high Ts values. However, the highest residuals of ETa images occurred on the surfaces with milder Ts and higher evapotranspiration rates (irrigated surfaces).

Highlights

Evapotranspiration is a key factor for determining the water balance and water demand for crops (Sánchez et al, 2008; French et al, 2015)
normalized difference vegetation index (NDVI) shows the dynamics of vegetation vigor and allows inferring with the spatial behavior of Ts and ETa
NDVI (Figure 2) showed that the region presented areas with a predominance of vegetation in its pixels, which was evidenced by high NDVI values

Summary

Introduction

Evapotranspiration is a key factor for determining the water balance and water demand for crops (Sánchez et al, 2008; French et al, 2015). The estimation of evapotranspiration requires that the sensor on board the satellite can capture information emitted from the surface and relative to the electromagnetic spectrum of the thermal infrared (Bastiaanssen, 2000; Li et al, 2013; Jimenez-Bello et al, 2015) This spectrum is necessary to estimate the surface temperature, a parameter required in the calculation of evapotranspiration (Bastiaanssen, 2000; Teixeira, 2010; Santos et al, 2011; Li et al, 2013; Andrade et al, 2014; Teixeira et al, 2015; Coaguila et al, 2017)

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