Evapotranspiration (ET) is a key process in the hydrological cycle. A sound understanding and quantification of ET is an integral part of understanding and predicting the water balance changes due to land use and climate change. Estimating ET is prone to large uncertainties, and advances in measurements of transpiration as well as evaporation are sorely needed, both for system understanding and for validation of remotely sensed products and improving models. The latter requires upscaling from point measurements to spatial estimates which remains a crucial challenge in (eco-)hydrological modelling.

This session will mainly focus on the measurement of ET with in-situ devices like lysimeters, sap flow sensors, eddy covariance, scintillometers, Bowen ratio method and other approaches. Additionally, we want to address the spatio-temporal scale gap between the various in-situ approaches themselves as well as between in-situ data, remote sensing products and catchment-scale modelled ET. We thus welcome contributions that (1) assess and compare the quality of known and new in-situ ET measurements, (2) analyse ET trends in time series and ET spatial patterns and their controls, (3) include cross-scale comparisons and scaling approaches and (4) incorporate in-situ measurements into modeling approaches.

For other ET sessions, with a focus on catchment hydrology, especially in extreme and sensitive environments, see HS2.1.1; with a focus on arid and semi-arid environments, see HS6.5.