Abstract
Precipitation deficit and more extreme drought and precipitation events are expected to increase in the Mediterranean region due to global warming. A great part of this region is covered by olive orchards, representing 97.5% of the world's olive agricultural area. Thus, the adaptation of olive cultivation demands climate-smart management, such as the optimization of water use efficiency, since evapotranspiration is one of the most important components of the water balance. The novelty of this work is the combination of the remote sensing data fusion and the Two Source Energy Balance (TSEB) model (through Sentinel-2 and Sentinel-3 imagery) to estimate the actual daily evapotranspiration (ETd), at high spatial (20 m) and temporal (daily) resolution, in an olive orchard under two management regimes: herbaceous free (HF) and herbaceous-cover (HC); along a three years period, based on the hypothesis that TSEB is still able to track and estimate the evapotranspiration over more complex canopies. The study was carried out from 2016 to 2019 in an olive orchard in the South of Spain, where the flux estimates were validated and assessed by in situ eddy covariance (EC) measurements. The results show better agreement in HC for net radiation (Rn) and the soil heat flux (G), but similar for both surfaces regarding the sensible (H) and latent (λE) heat fluxes, as well as ETd. On both surfaces greater differences obtained at higher H, and the magnitude of overestimation of λE and ETd were influenced by the EC energy imbalance. By contrast, G was overestimated with HC probably influenced by herbs, and equally underestimated for HF surfaces. The obtained results are in agreement with similar studies in tree crop orchards, and show the consistency of the used methodology and its usefulness for some farming activities, even on the more heterogeneous surface.
Highlights
In recent years, there has been an increase in impacts on the Earth ecosystems caused by weather and climate events amplified by climate change
The modelled pixel values selected for H and λE fluxes validation were the pixel where the peak of maximum influence of eddy covariance (EC) footprint is located at the satellite overpass time which was weight averaged (50%) together with the adjacent pixels (50% remainder), following the foot print model described in Schmid (2002)
The modelled pixel value selected for validate Rn and G was the fuchsia pixel which run into the pixels of both EC towers where the sensors for measuring these variables are installed
Summary
There has been an increase in impacts on the Earth ecosystems caused by weather and climate events amplified by climate change. These events produce displacement, migrations and important consequences on human health, socio-economic development, and food security (Kappelle et al, 2020; UNESCO and UN-Water, 2020). Due to more extreme precipitation and drought events, precipitation deficits are likely in the Mediterranean region (Lionello and Scarascia, 2018; UNDRR, 2019; UNESCO and UN-Water, 2020). Water resources and productivity maximization can play a very important part in
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