Preprints
https://doi.org/10.5194/egusphere-2024-3386
https://doi.org/10.5194/egusphere-2024-3386
19 Nov 2024
 | 19 Nov 2024
Status: this preprint is open for discussion.

Assessing evapotranspiration dynamics across central Europe in the context of land-atmosphere drivers

Anke Fluhrer, Martin Baur, María Piles, Bagher Bayat, Mehdi Rahmati, David Chaparro, Clémence Dubois, Florian Hellwig, Carsten Montzka, Angelika Kübert, Marlin Mueller, Isabel Augscheller, Francois Jonard, Konstantin Schellenberg, and Thomas Jagdhuber

Abstract. Evapotranspiration (ET) is an important variable for analysing ecosystems, biophysical processes, and drought-related changes in the soil-plant-atmosphere system. In this study, we evaluated freely available ET products from satellite remote sensing (i.e., MODIS, SEVIRI, and GLEAM) as well as modelling and reanalysis (i.e., ERA5-land and GLDAS-2) together with in-situ observations at eight Integrated Carbon Observation System (ICOS) stations across central Europe between 2017 and 2020. The land cover at the selected ICOS stations ranged from deciduous broad-leaved, evergreen needle-leaved, and mixed forests to agriculture. Trends in ET were analysed together with soil moisture (SM) and water vapor pressure deficit (VPD) during four years including a severe summer drought in 2018, but contrasting wet conditions in 2017. The analyses revealed the increased atmospheric aridity and decreased water supply for plant transpiration under drought conditions, showing that ET was generally lower and VPD higher in 2018 compared to 2017. Across the study period, results indicate that during moisture limited drought years, ET is strongly decreasing due to decreasing SM and increasing VPD. However, during normal or rather wet years, when SM is not limited, ET is mainly controlled by VPD, and hence, the atmospheric demand.

The comparison of the different ET products based on time series, statistics, and extended triple collocation (ETC) shows in general a good agreement with ETC correlations between 0.39 and 0.99 as well as root-mean-square errors lower than 1.07 mm/day. The greatest deviations are found at the agricultural-managed sites Selhausen (Germany) and Bilos (France), with the former also showing the highest potential dependencies (error cross-correlation) between the ET products. Our results indicate that ET products differ most at stations with spatio-temporal varying land cover conditions (varying crops over growing periods and between seasons). This complex heterogeneity complicates the estimation of ET, while ET products agree at evergreen needle-leaved stations with less temporal changes throughout the year and between years. The ET products from SEVIRI, ERA5-land, and GLEAM performed best when compared to ICOS observations with either lowest errors or highest correlations.

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Anke Fluhrer, Martin Baur, María Piles, Bagher Bayat, Mehdi Rahmati, David Chaparro, Clémence Dubois, Florian Hellwig, Carsten Montzka, Angelika Kübert, Marlin Mueller, Isabel Augscheller, Francois Jonard, Konstantin Schellenberg, and Thomas Jagdhuber

Status: open (until 31 Dec 2024)

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Anke Fluhrer, Martin Baur, María Piles, Bagher Bayat, Mehdi Rahmati, David Chaparro, Clémence Dubois, Florian Hellwig, Carsten Montzka, Angelika Kübert, Marlin Mueller, Isabel Augscheller, Francois Jonard, Konstantin Schellenberg, and Thomas Jagdhuber
Anke Fluhrer, Martin Baur, María Piles, Bagher Bayat, Mehdi Rahmati, David Chaparro, Clémence Dubois, Florian Hellwig, Carsten Montzka, Angelika Kübert, Marlin Mueller, Isabel Augscheller, Francois Jonard, Konstantin Schellenberg, and Thomas Jagdhuber
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Latest update: 19 Nov 2024
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Short summary
This study compares established evapotranspiration products in Central Europe and evaluates their multi-seasonal performance during wet & drought phases between 2017–2020 together with important soil-plant-atmosphere drivers. Results show that SEVIRI, ERA5-land & GLEAM perform best compared to ICOS measurements. During moisture limited drought years, ET is decreasing due to decreasing soil moisture and increasing vapor pressure deficit, while in other years ET is mainly controlled by VPD.