What is it about?
During sunny summer days, trees are able to modify gravity at the level of a tenth of a billionth of g. As water evaporates and transpires from the forest, the mass distribution of water decreases, changing the gravity field. The water mass loss can be directly inferred from continuous gravity measurements.
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Why is it important?
The global evapotranspiration is more than 85% made up of canopy transpiration, which returns more than 50% of precipitation back to the atmosphere. In arid to semiarid environments evapotranspiration can return more than 95% of the annual precipitation; hence, its assessment is critical to assess recharge. Evapotranspiration plays a major role in terrestrial ecosystems. It has a major impact on the global fresh water availability. Furthermore, evapotranspiration strongly controls energy transfer between the Earth and the atmosphere and hence within the global climate system
Perspectives
New methods to estimate evapotranspiration should be validated and calibrated on a site where a superconducting gravimeter provides an independent estimate. We think that the ideal site would be in a flat forested area (if possible, installing the gravimeter in a shaft), with lower underground hydraulic conductivity.
Dr Michel J Van Camp
Royal Observatory of Belgium
Read the Original
This page is a summary of: Direct measurement of evapotranspiration from a forest using a superconducting gravimeter, Geophysical Research Letters, October 2016, American Geophysical Union (AGU),
DOI: 10.1002/2016gl070534.
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