Co-Developing Metadata Standards for In-Situ ET Measurements

Evapotranspiration (ET) constitutes one of the most significant fluxes of matter and energy within terrestrial ecosystems and serves as a key indicator of landscape functioning. A range of in situ measurement techniques—such as lysimeters, eddy covariance systems, and sap flow sensors—are now widely employed in monitoring networks and research initiatives to obtain high-quality field observations. These datasets offer substantial potential for secondary use, including methodological intercomparisons and refinements, upscaling efforts, and analyses of large-scale or long-term patterns. However, effective and efficient data reuse—and thus scientific progress—is frequently hindered or rendered impossible by insufficient or missing metadata.Previous sessions at EGU General Assemblies focusing on in situ and remote-sensing-based ET have highlighted the need to support comparisons of ET estimates obtained with different methods and to enable informed reuse of existing data. Given the rapid growth of available datasets and the increasing importance and potential of data reuse, there is an urgent need to reduce this persistent bottleneck caused by insufficient metadata. In response, we initiated a collaborative working group to address this issue by developing a set of standardized templates for relevant metadata and uncertainty information. These templates build upon and extend existing initiatives, including ICOS, FLUXNET, and SAPFLUXNET, and are tailored to eddy covariance, sap flow, and lysimeter measurements.We present the templates, highlight their differences from existing initiatives and standards, and we outline our vision for future use cases, e.g. in inter-method comparisons and modelling studies enabled by the enhanced metadata descriptions. We invite feedback from the data producers whether the templates facilitate providing metadata, increasing the re-usability of the data; and from the data users on whether the proposed metadata templates meet their needs. Based on community input, we aim to further refine the templates to support useful and sustainable data description.