Quantifying and partitioning forest evapotranspiration based on co-located radar and flux tower measurements

Research Project, 2020 – 2023

Evaporation and transpiration from the land surface, termed evapotranspiration (ET), play a crucial role in the energy and water balance at the land surface. ET and its components are thus critical variables in models of the regional and global climate and the hydrological cycle. Spatial and temporal variability makes ET extremely difficult to measure over large spatial scales with fine spatial resolution.

Important problems surround the lack of spatially-distributed, long-term ET observations: 1) There is disagreement on whether forests are net users or net producers of rainfall. 2) It is uncertain whether global warming will lead to intensification of the water cycle.3) The role of forests in the global climate is poorly modelled in global climate models. New ET measurement methods are urgently needed to resolve these issues. The aim of this project is to study the relationship between radar measurements and ET in forests with the driving goal of observing forest ET globally with high spatial and temporal resolution using satellite radar sensors.

Two of Sweden’s leading forest research infrastructures will be merged: a radar tower and an experimental forest equipped with a flux tower based the eddy covariance technique. This unique experiment will be used to develop the first-ever models for relating radar observables with different frequencies, polarisations and observation scenarios to ET and its components using measurement data at timescales of hours to years.