Abstract
Evapotranspiration (ET) is a key parameter in the description of the energy and water fluxes over land. Continuous and spatially detailed ET simulations are thus required for a number of scientific and management-related purposes. These conditions are determined by the modelling approach and the composition of the forcing dataset. This study aimed at simulating daily ET in a diversity of climate and land cover conditions at a spatial resolution of ∼1 km and higher. The modelling approach was based on the algorithm driving the ET product developed and set in operations in the framework of the Satellite Application Facility on Land Surface Analysis programme (LSA-SAF). The implemented algorithm allowed the ingestion of biophysical parameters derived from SPOT-V and PROBA-V observations developed by the Copernicus Global Land Programme, as well as other model parameters at a similar spatial resolution. The model was tested at an ∼1 km spatial resolution in over 40 sites located in different climate and land cover contexts. The implementation at ∼300 m was tested in the upper Biebrza basin, in Poland. The simulations correlated well with the validation dataset (r2 > 0.75 in 80% of sites) and exhibited root mean squared values lower than 1 mm/day in 80% of the cases. The results also pointed to the need for refining the accuracy of soil moisture data sources, especially in dry areas. The results showed the ability of the modelling approach and the SPOT-V/PROBA-V missions to support the generation of long ET time series. They also opened the gate to incorporate Sentinel-3 in ET continuous modelling.
Highlights
The timing and magnitude of energy and water fluxes at the Earth’s surface result from the interplay of a number of processes and conditions in the soil-plant-atmosphere continuum
This study aimed at conducting daily ET simulations at an ∼1 km spatial resolution in a variety of climate and land cover conditions
The approach relied on the principles behind the Land Surface Analysis Satellite Application Facility (LSA-SAF) ET algorithm and the adequacy of biophysical variables derived from SPOT-V and PROBA-V to integrate the forcing dataset
Summary
The timing and magnitude of energy and water fluxes at the Earth’s surface result from the interplay of a number of processes and conditions in the soil-plant-atmosphere continuum. The accurate and timely estimation of this component of the water balance is relevant in a large number of domains like agriculture monitoring and yield prediction [1], drought assessment [2,3,4], water catchments’ management [5,6], urban planning [7,8], etc. The heating effect of solar energy on Earth is tightly connected to ET as a substantial fraction of the solar radiation triggers the evaporative process (latent heat flux). The resulting ET rates depend on local conditions (like water vapour demand, soil moisture, land cover, etc.)
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