Towards Gridded Evapotranspiration Estimation for Ireland: A Mapping and Modelling Approach

Evapotranspiration (ET) is a key component of the coupled water and energy cycles, linking land–atmosphere exchange with hydrological response. However, generating spatially continuous and reliable ET datasets remains challenging. This is especially true in regions such as Ireland, where persistent cloud cover limits satellite retrievals and ground-based observations are sparse. Enhancing spatial ET estimation is therefore essential for a range of applications, from hydrological monitoring and water resource management to agricultural planning and climate adaptation.

This study presents a framework for gridded ET estimation over Ireland that combines data-driven correction with physically based land-surface modelling. The framework builds on an adaptive bias correction (AB) method and a dynamic multi-product combination (COM) method developed previously to improve ET estimates from multiple products at 21 station locations across Ireland. While these methods improve ET estimation at point locations, extending them to spatially continuous maps requires suitable interpolation and modelling approaches.

The framework has two complementary components. The first uses spatial interpolation by kriging to extend bias-corrected ET estimates beyond station locations and generate gridded ET maps across Ireland, with particular attention to performance in regions with limited observational coverage. The second uses the Surface Externalisée (SURFEX) land surface model to generate physically based ET estimates, providing an independent process-based representation of ET. Both components are evaluated against eddy-covariance measurements from the Irish National Agricultural Soil Carbon Observatory (NASCO) flux tower network, an extensive network covering a range of land uses across Ireland.

This work forms part of the broader Evapotranspiration for Ireland (ET4I) project, which aims to develop high-resolution gridded ET maps nationwide. The evaluation presented here represents a step towards more reliable national-scale ET mapping in Ireland and offers a basis for improved hydrological, agricultural, and environmental applications in cloud-prone, data-limited environments.