Calibration of METRIC Model to Estimate Energy Balance over a Drip-Irrigated Apple Orchard

Daniel De La Fuente-Sáiz,David Fonseca,Samuel Ortega-Farías,Ayse Kilic,Richard Allen,Samuel Ortega-Salazar

doi:10.3390/rs9070670

Daniel De La Fuente-Sáiz, David Fonseca + Show 4 more

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https://doi.org/10.3390/rs9070670

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Abstract

A field experiment was carried out to calibrate and evaluate the METRIC (Mapping EvapoTranspiration at high Resolution Internalized with Calibration) model for estimating the spatial and temporal variability of instantaneous net radiation (Rni), soil heat flux (Gi), sensible heat flux (Hi), and latent heat flux (LEi) over a drip-irrigated apple (Malus domestica cv. Pink Lady) orchard located in the Pelarco valley, Maule Region, Chile (35°25′20′′LS; 71°23′57′′LW; 189 m.a.s.l.). The study was conducted in a plot of 5.5 hectares using 20 satellite images (Landsat 7 ETM+) acquired on clear sky days during three growing seasons (2012/2013, 2013/2014 and 2014/2015). Specific sub-models to estimate Gi, leaf area index (LAI) and aerodynamic roughness length for momentum transfer (Zom) were calibrated for the apple orchard as an improvement to the standard METRIC model. The performance of the METRIC model was evaluated at the time of satellite overpass using measurements of Hi and LEi obtained from an eddy correlation system. In addition, estimated values of Rni, Gi and LAI were compared with ground-truth measurements from a four-way net radiometer, soil heat flux plates and plant canopy analyzer, respectively. Validation indicated that LAI, Zom and Gi were estimated using the calibrated functions with errors of +2%, +6% and +3% while those were computed using the standard functions with error of +59%, +83%, and +12%, respectively. In addition, METRIC using the calibrated functions estimated Hi and LEi with error of +5% and +16%, while using the original functions estimated Hi and LEi with error of +29% and +26%, respectively.

Highlights

Water scarcity has become a main limiting factor for agriculture, especially in arid and semi-arid conditions
The main goals of this research were to calibrate the sub-models to compute leaf area index (LAI), Gi and Zom and to validate the METRIC model to compute the instantaneous values of Rni, Gi, Hi and LEi over a drip-irrigated apple orchard under
Results indicated that METRIC using the original, standard functions underestimated Hi by Results indicated that METRIC using the original, standard functions underestimated Hi by about about 29% with root-mean-square error (RMSE) and mean absolute error (MAE) ranging 80–95

Summary

Introduction

Water scarcity has become a main limiting factor for agriculture, especially in arid and semi-arid conditions This issue has become relevant in countries like Chile where many commercial apple orchards have been transformed from traditional to intensive (1500 tree·ha−1 ) or super-intensive (3500 tree·ha−1 ) planting densities that require the optimization of water application and reduction of the cost of electrical energy required for pumping water into orchards. ETa is calculated by multiplying the reference evapotranspiration (ETr) by a crop coefficient (Kc) which depends on crop type and the crop growth stage [1,2] This procedure is based on the Penman–Monteith (PM) equation, which computes daily ETr values over a reference surface (alfalfa or grass) using weather-based data from an automatic weather station (AWS) [3,4]. Kc values for complex, heterogeneous canopies such as fruit orchards depend highly on canopy architecture, plant densities, and standard agronomical practices that determine the partitioning of ETa into transpiration and soil evaporation [7]

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