The CCI Land Evaporation project aims to deliver the first long-term, high-resolution global dataset of land evaporation and its main components: plant transpiration, bare soil evaporation, interception loss, latent heat flux, and sensible heat flux. This project will support climate science, enhance climate services, and provide valuable inputs for water management and adaptation strategies by improving the accuracy and consistency of these Essential Climate Variables (ECVs) . The resulting datasets will help detect trends, reduce uncertainties in the global water cycle, and strengthen the scientific basis for climate policy.

Background

Land evaporation plays a key role in the water, carbon, and energy cycles. By regulating water availability and acting as a natural cooling mechanism, it influences ecosystems, agriculture, and human societies. Evaporation also modulates extreme events such as droughts and heatwaves, while feedbacks involving water vapour, clouds, and atmospheric stability shape regional climate patterns and the global energy balance.

Recognising its importance for the climate system and the need for systematic monitoring, the Global Climate Observing System (GCOS) has designated land evaporation as one of the Essential Climate Variables (ECVs). In particular, its main components, plant transpiration, interception loss, and bare soil evaporation, are now acknowledged as crucial for understanding land–atmosphere interactions and their role in climate change.

Despite this recognition, land evaporation remains one of the most uncertain variables of the global water cycle. Direct observations at large scales are not possible, and ground-based measurements remain sparse and unevenly distributed, especially in the Global South. Modelling is equally challenging, as evaporation is controlled by a range of interacting processes, including plant physiology, turbulence, and soil–vegetation–atmosphere feedbacks.

Recent advances in satellite remote sensing and process-based modelling now make it possible to estimate land evaporation and its components with unprecedented accuracy, consistency, and coverage.

Building on these advances, the CCI Land Evaporation project, as part of ESA’s Climate Change Initiative (CCI) leverages satellite observations to deliver a long-term, global dataset of land evaporation tailored to scientific requirements and policy needs.

This dataset will improve our understanding of land–climate interactions, support the evaluation of climate models, and support water resource management and climate adaptation strategies.

Land evaporation plays a key role in the water, carbon, and energy cycles.
Land evaporation plays a key role in the water, carbon, and energy cycles.

Aims and objectives

The main objective of this project is to enhance ESA’s CCI portfolio by producing a long-term, high-accuracy dataset of land evaporation and its components. The specific objectives are to:

  1. Incorporate user requirements into the final datasets through consultations with the climate science and service communities, supported by a review of international guidelines.
  2. Develop a state-of-the-art evaporation algorithm with a modular design that represents diverse evaporation processes, quantifies uncertainty, and enables alternative process formulations.
  3. Implement a processing system to generate and deliver open, reproducible, quality-controlled datasets that are fully compliant with CCI standards.
  4. Validate product accuracy and reliability through intercomparison with existing datasets and in situ measurements.
  5. Assess usability in climate and hydrometeorological applications via targeted case studies that demonstrate value for science and decision-making.