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CHORALE: CAPTURING CRITICAL HYDROLOGY FEEDBACKS IN EARTH SYSTEM MODELS FOR ROBUST CLIMATE ASSESSMENTS IN WATER LIMITED REGIONS (CHORALE)
Proposal responding to Horizon CL5-2026-08-Two-Stage-D1-06 . Budget up to 9 M Euro.
Consortium: CNR, ECMWF, CNRM, JULICH, NORESM, TUDelft, TUWien, UniBo, CNR-IRPI, CICERO, Imperial, LUND.
The proposal is envisaging a 5 year project with a 9 M Euro envelope. The work will focus on: Closing Critical Terrestrial Water-Cycle Gaps in Earth System Models: Linking Physical Processes, Biosphere Feedbacks, and Climate Assessment.
Water gaps are for instance related to water redistribution when irrigation and inundation occurs influencing evaporation, infiltration and runoff processes. Traditional land surface models do not represent well these processes. A link with the research done by consortium members is anticipated provide extra resources. The vegetation sensitivity to water management and post-inundation can be examined and is anticipated to have atmospheric and hydrological impact. ECMWF is proposing to lead a WP1 for the modelling and contribute to WP3/WP4 for simulation and assessment, with an expected PM funding 1 FTE for 5-years.
ECMWF can participate with ecLand model, CaMa-Flood inundation model, and the P-Model (phenology) that can be run offline or coupled with IFS. AILand is also considered to expand the variables simulated and compare with other LSMs and AI-LSMs.
The CHORALE project addresses a critical gap identified in the IPCC Sixth Assessment Report (AR6) Working Group I: the inadequate representation of the continental water cycle in Earth System Models (ESMs), which remains a major source of uncertainty in climate projections, especially in water-limited and transitional regions such as Mediterranean climates. Current ESMs often rely on simplified, non–scale-aware hydrological formulations that fail to capture key processes such as groundwater dynamics, irrigation feedbacks, and surface–subsurface interactions. These limitations hinder the accurate simulation of nonlinear feedbacks between water, energy, and carbon cycles.
CHORALE aims to advance climate modelling by developing an integrated, scale-aware representation of hydrological processes including irrigation and inundation and their coupling with vegetation dynamics, surface energy balance, and the terrestrial carbon cycle. Water availability governs evapotranspiration and energy partitioning, thereby influencing land–atmosphere interactions, temperature variability, and vegetation water stress. In turn, vegetation responses regulate ecosystem productivity and carbon uptake. Misrepresentation of these interactions propagates uncertainty in projections of terrestrial carbon sinks, which are central to climate mitigation strategies.
The project also addresses the nonlinearity of hydrology-driven ecosystem responses. Persistent soil moisture deficits and groundwater depletion can trigger abrupt shifts in vegetation functioning, potentially turning ecosystems from carbon sinks into sources. Such tipping points and cascade effects are poorly represented in current models. By improving hydrological realism and coupling processes, CHORALE seeks to better capture these dynamics.
A coordinated multi-model strategy involving platforms such as ECMWF, EC-Earth, ICON-ESM, and others will ensure robustness and enable uncertainty quantification. The project will conduct policy-relevant simulations aligned with CMIP7 and related Model Intercomparison Projects, including innovative “What-if” scenarios such as large-scale regreening initiatives in semi-arid regions. These experiments will assess the sustainability, benefits, and risks of land-based mitigation strategies.
Overall, CHORALE will deliver more credible, policy-relevant climate reanalyses prototypes and future projections, strengthening the scientific basis for climate adaptation, mitigation, and international assessments.
Benefits for ECMWF:
The CHORALE project offers significant strategic and scientific benefits for ECMWF, directly aligning with its mission to advance Earth system monitoring, prediction, and deliver policy-relevant climate information.
First, it strengthens ECMWF’s leadership in Earth system modelling by advancing the representation of hydrology within the IFS, including processes such as groundwater dynamics, inundation, and irrigation. This is highly complementary to ongoing developments in ecLand and coupled hydrological frameworks (e.g., CaMa-Flood), reinforcing ECMWF’s position at the forefront of land–atmosphere coupling research.
Second, CHORALE enhances forecast skill across timescales. Improved water–energy–carbon coupling will lead to better representation of soil moisture, evapotranspiration, and land feedbacks, thereby improving sub-seasonal to seasonal prediction, drought monitoring, and extreme event forecasting—core service areas for ECMWF and the Copernicus Climate Change Service.
Third, the project strengthens ECMWF’s contribution to international programmes and assessments, including future IPCC reports and CMIP7 via EC-Earth. By addressing a major source of uncertainty in climate projections, ECMWF can play a central role in delivering more credible climate information to policymakers.
Finally, participation in a coordinated multi-model consortium enhances collaboration with leading ESM centres, increases visibility in European flagship initiatives, and positions ECMWF to influence emerging policy-relevant experiments, such as large-scale regreening scenarios and water management for optimal agriculture yields.
Early Meetings and Material:
Concatenated minutes of all scoping meetings past weeks :
MINUTES OF SCOPING MEETINGs 13/02-16/02-18/02 concatenated
According with the discussion the concept note has been updated also including comments and some discussion with Rosie Fisher (NorESM), who was invited to join (according with the discussion) and expressed interest in our consortium:
CONCEPT NOTE UPDATE
Some additional working material (including infographics and first tentative WP structure to be discussed) was added to the updated presentation slides at following link:
SCOPING MEETING PRESENTATION UPDATE