First Evidence of Correlation Between Evapotranspiration and Gravity at a Daily Time Scale From Two Vertically Spaced Superconducting Gravimeters

Abstract

Evapotranspiration (ET) is a key variable to understanding eco-hydrosystems because it links water, carbon, and energy cycles (Fisher, 2014). ET is a major component of the water cycle, accounting for approximately 70% of precipitated water at the continental scale (Fisher et al., 2017;Oki & Kanae, 2006). Several approaches exist for estimating ET, but large uncertainties persist and estimates remain difficult to validate, particularly at large scale (Müller & Bolte, 2009;Verstraeten et al., 2008). New approaches for estimating ET are crucially needed to improve our understanding of related processes.Gravimetry is a geophysical method that measures the gravitational acceleration field (g). During the last decades, progress has led to the development of devices that can now achieve precision of a few nm/s 2 and obtain highly accurate temporal monitoring (Van Camp et al., 2006). These advances now allow to study the dynamics of ET. Data from the GRACE (Gravity Recovery and Climate Experiment) satellite have been used to study ET (Long

The geophysical toolbox applied to forest ecosystems – A review

“…They interpreted the daily change in the gravity signal as water loss through evapotranspiration. Carrière et al (2021a) showed a day-to-day correlation between the daily variation of gravity and the modelled ET of a Mediterranean holm oak (Quercus ilex L.) forest. In their study, the authors subtract the signal of two superconducting gravimeters superimposed onto each other with a 500 m altitude difference to achieve the accuracy needed to interpret the evapotranspiration signal.…”

Superconducting Gravimeters: A Novel Tool for Validating Remote Sensing Evapotranspiration Products

“…Due to these characteristics, SGs have been used as hydrological sensors for calibration and validation of hydrological models [24], for monitoring the artificial recharge of an aquifer [25], and for estimating specific yields [26]. In addition, SG data can be used to estimate ET at the mesoscale [8,[27][28][29][30]. Van Camp et al [27] applied a stacking process to gravity time series for rain-free periods to isolate the effect of ET on the gravimetric signal and thus estimate the daily mean ET rate.…”

“…These ET estimates were then validated with data recorded by a lysimeter. Carrière et al [28] estimated daily ET in a rain-free period using data from two superconducting gravimeters vertically separated by a distance of 512 m. This arrangement between the gravimeters eliminates the non-hydrological large-scale effects observed by both instruments, improving the analysis of local water storage changes.…”