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The aim of this presentation is to report on recent advances concerning the satellite based soil moisture validation done through the ESA project “Fiducial Reference Measurement for Soil Moisture (FRM4SM)”. The main objective of this two years project (May 2021 - May 2023) is to study the means to inform on the confidence in soil moisture data products for the whole duration of a satellite mission. Composed of three international partners (AWST, CESBIO and TU WIEN), it aims at the identification and creation of standards for independent, fully characterized, accurate and traceable (i.e., fiducial) in situ soil moisture reference measurements with corresponding independent validation methods and uncertainty estimations for a satellite mission. The ground reference data is drawn from the International Soil Moisture Network (ISMN). New quality indicators are created to better characterize the aptness of ISMN measurements for satellite soil moisture validation, and protocols provided to identify a select set of fiducial reference data. The satellite part, in charge of independent validation methods, focuses efforts towards the Soil Moisture Ocean Salinity (SMOS) mission from ESA. Finally, the easy-to-use interface for the comparison of satellite soil moisture data against land surface models and in situ data, the Quality Assurance for Soil Moisture (QA4SM), targets to implement all created FRM protocols from ground measurement to validation methods created within the FRM4SM project.

To this day, in situ soil moisture data is viewed as ground truth by the satellite soil moisture (SSM) community. In general, little is still commonly known regarding the traceability of ground measurement uncertainty and their overall in uncertainty budget, which can impact satellite SSM product quality assessments.Within ESA’s “Fiducial Reference Measurement for Soil Moisture (FRM4SM, May 2021 - May 2023)” project, objectives are set towards building fully characterized and traceable (i.e., fiducial) in situ measurements following community-agreed guidelines from the GEOS/CEOS Quality Assurance for Soil Moisture (QA4EO) framework. These so called “fiducial reference data” (FRM) should have associated Quality Indicators (QI) attached to evaluate their fitness for purpose building upon agreed reference standards (SI if possible). Moreover, such data should be easily and openly accessible, validation case studies should demonstrate their utility and reliability, and protocols and procedures should be established for the usage of such FRM datasets to make scientific studies intercomparable and reproducible.As part of the FRM4SM project, the following questions were addressed using the International Soil Moisture Network (ISMN) as a ground reference database and the Soil Moisture and Ocean Salinity (SMOS) mission as an example satellite product:(1) What makes “fiducial reference data” fiducial?(2) Is the creation of a globally-representative FRM subset already feasible for SSM?(3) What are the current limitations of in situ observations that limit fiduciality?(4) What is needed to create a full traceability chain from in situ point measurements to the satellite footprint scale?In this presentation, we will discuss these questions in detail and report on related findings of the FRM4SM project.

Quality assessment is an integral part of creating climate data records. Producers of satellite based records want to evaluate whether their products fulfill certain quality requirements, such as the ones set by the Global Climate Observing System (GCOS) of the World Meteorological Organization (WMO) or by the Committee on Earth Observation Satellites (CEOS). Users of these data, on the other hand, are usually interested in their fitness-for-purpose in terms of specific applications, temporal/spatial subsets, and how different data sets of the same variable compare to each other.Quality Assurance for Soil Moisture (QA4SM) is an online validation service for (inter)comparing soil moisture records and assessing their quality, incorporating best practices, in a standardized, traceable way via an easy-to-use graphical user interface. The processing chain includes automatic preprocessing (filtering, temporal/spatial matching, scaling) of input data and computation of a set of quality metrics (e.g., correlation, bias, signal-to-noise-ratio). It provides an open and flexible framework in which users can upload their own data for comparison to state-of-the-art records that are already integrated in the service. These include reference data from the International Soil Moisture Network (ISMN), reanalysis data from ERA5 and GLDAS Noah, and various satellite based records such as SMOS, SMAP, Sentinel-1, ESA CCI, and C3S. In this presentation we give insight into the scientific and technical background of developing a cloud-based validation service and its current capabilities. We explain the advantages a service like this has, and how it can benefit users of climate data records with minimal effort.The service was launched as part of the Quality Assurance for High Spatial and Temporal Resolution Soil Moisture Data (QA4SM-HR) project through the Austrian Research Promotion Agency (FFG) and is currently developed within the framework of the European Space Agency’s Fiducial Reference Measurement for Soil Moisture (FRM4SM) project. It can be accessed at: https://qa4sm.eu

Soil moisture is recognized as an Essential Climate Variable (ECV), because it is crucial to assess water availability for plants and hence food production. Having long time series of freely available and interoperable soil moisture data with global coverage enables scientists, farmers and decision makers to detect trends, assess the impacts of climate change and develop adaptation strategies.The collection, harmonization and archiving of in situ soil moisture data was the motivation to establish the International Soil Moisture Network (ISMN) at the Vienna University of Technology in 2009 as a community effort. Based on several project funding periods by the European Space Agency (ESA), the ISMN became an essential means for validating and improving global land surface satellite products, climate and hydrological models.Permanent funding for the ISMN operations was secured through the German Government (Ministry of Digital and Transport) and therefore the ISMN has successfully migrated at the end of 2022 to its new host the International Centre for Water Resources and Global Change (ICWRGC) and the German Federal Institute of Hydrology (BfG). Furthermore, the ISMN was recognized by WMO in their latest State of Global Water Resources report.To improve the data service delivery, ISMN users can now benefit from a newly developed dataviewer which features functionalities such as data archives and advanced filter options (e.g. for climate and landcover types, for data quality) developed in synergies with the ESA project Fiducial Reference Measurements for Soil Moisture (FRM4SM). This presentation aims at showcasing these latest upgrades as well as new network contributions to the ISMN.

Soil moisture is recognized as an Essential Climate Variable (ECV) because it is crucial for assessing water availability for plants and hence food production. Having long time series of freely available soil moisture data with global coverage enables scientists, farmers and decision makers to detect trends, assess the impacts of climate change, and develop adaptation strategies. The collection, harmonization and archiving of in situ soil moisture data was the motivation to establish the International Soil Moisture Network (ISMN) at TU Wien, with the financial support of the European Space Agency (ESA), in 2009 as a community effort. The ISMN became an essential source for validating and improving global satellite products, and climate, land surface, and hydrological models. In 2021 permanent funding for the ISMN operations was secured through the German Government (Ministry of Digital and Transport). The transfer of the ISMN to its new host, i.e., the International Centre for Water Resources and Global Change (ICWRGC)/German Federal Institute of Hydrology (BfG), took place during 2021/2022. The takeover posed the challenge to migrate an operational service between two different teams, locations/hardware and organisations. Finally, the ISMN started serving data from its new host in December 2022 while keeping the service continuously running throughout the migration. In parallel the team in Vienna developed and launched a new dataviewer. This presentation aims at showcasing new ISMN features as well as recent data contributions as well as next evolution of the ISMN based on synergies and science outcome of the Research and Development activities performed by ESA in the context of the Fiducial Reference Measurements for Soil Moisture (FRM4SM) project.

For over a decade, the International Soil Moisture Network (ISMN) has been providing free in-situ soil moisture data for validating and improving global satellite soil moisture products, weather prediction, agricultural activities, research and training as well as for the development of hydrological models. The ISMN is a community-wide effort and aggregates soil moisture observations from several organizations, harmonizes them and provides a centralized platform where end users can access them. Presently, the ISMN consists of over 72 soil moisture networks and more than 2800 stations spread across the globe. For more than a decade, the ISMN has been funded by European Space Agency and established, developed and maintained by Vienna University of Technology (TU Wien), Austria.For continuing development, outreach and maintenance of the ISMN, a sustainable and long-term support is required. In order to achieve such long-term support, the ISMN will be transferring to the German Federal Institute of Hydrology (BfG) and connected International Center for Water Resources and Global Change (ICWRGC) in Germany within 2022. While BfG and ICWRGC (operating under the auspice of UNESCO and WMO) will host and maintain the ISMN data facility, long-term financial support will be provided by the German Federal Institute of Hydrology through the Federal Ministry of Digital Infrastructure and Transport.The ICWRGC has being coordinating the Global Terrestrial Network – Hydrology (GTN-H) as well as Global Environment Monitoring System for Freshwater (GEMS/Water Data Center) for several years. Hence, the center has an extensive experience, resources as well as scientific advisory support for a long-term sustainable operation and maintenance of the ISMN. As we look forward to a new future of ISMN, we also want to maintain, even improve on the great community support the project has received.Therefore, our presentation aims to give an overview of the contribution of ISMN to research and training development, provides recent updates regarding the data service and ongoing technical developments. Furthermore, we want to introduce the new host as well as presenting the future outlook of the ISMN, which include setting up scientific advisory board with members from relevant UN organizations, key data providers and data users that would help promote and develop the ISMN further. Through the connection to UN organizations, member states could be encouraged to share their operational soil moisture data with the ISMN for continuing support of global climate and water resources observations. We also look forward to gaining new collaborations that will help in extending the ISMN database, initiate discussion between stakeholders to improve visibility and scientific advancement of the ISMN as well as promoting the importance of soil moisture within global earth observations data products.

With its steadily growing provider and user community (4000 active users), the International Soil Moisture Network (ISMN, https://ismn.earth) is a unique centralized global data hosting facility, making in-situ soil moisture data easily and freely accessible. The main goal of the ISMN in the past decade was to build up the harmonized and quality-controlled in-situ soil moisture source it is today.The ISMN provides benchmark data for several operational services such as ESA CCI Soil Moisture, the Copernicus Climate Change (C3S) and Global Land Service (CGLS), and the online validation tool QA4SM (https://qa4sm.eu). ISMN data is widely used for support of algorithm development and validation of different satellites, evaluation of soil moisture products, as a training set for various data-driven approaches, model developments, drought monitoring and diverse meteorological applications (Dorigo et. al 2021).In this presentation, we will provide an overview of the ISMN scientific achievements accomplished in the last decade, show recent scientific and service developments, and present foreseen future developments.We provide a review of hundreds of papers making use of ISMN data to identify major scientific breakthroughs facilitated through the ISMN. We also identify current limitations in data availability, functionality and challenges in data usage (e.g., in-situ data inclusion in data sparse regions, in-situ data inclusion from official governmental observation networks, data and measurement traceability, etc.).One of the major successes has been the achievement of long-term financial support for the ISMN through the German Ministry of Digital Infrastructure and Transport. Therefore, the ISMN operations is currently transferred from Vienna Austria (TU Wien) to the new host in Koblenz, Germany (International Center for Water Resources and Climate Change - ICWRGC, Federal Institute for Hydrology – BfG).This evolution not only opens up a stable future for the ISMN but also gives TU Wien once more the opportunity to focus on the scientific development of the ISMN as currently proceeded within the ESA project “Fiducial Reference Measurement for Soil Moisture (FRM4SM)”. Within this two-year project (May 2021 – May 2023) the goal is also to identify and create standards for independent, fully characterized, accurate and traceable in-situ soil moisture measurements (from the ISMN) with corresponding uncertainty estimations and independent validation methods (inserted in the QA4SM service: https://qa4sm.eu).

The International Soil Moisture Network (ISMN, https://ismn.earth) is international cooperation to establish and maintain a unique centralized global data hosting facility, making in-situ soil moisture data easily and freely accessible (Dorigo et al., 2021). Initiated in 2009 as a community effort through international cooperation (ESA, GEWEX, GTN-H, GCOS, TOPC, HSAF, QA4SM, C3S, etc.), the ISMN is an essential means for validating and improving global satellite soil moisture products, land surface-, climate-, and hydrological models. The ISMN is a widely used, reliable, and consistent in-situ data source (surface and sub-surface) collected by a myriad of data organizations on a voluntary basis. The in-situ soil moisture measurements are collected, harmonized in terms of units and sampling rates, advanced quality control is applied and the data is then stored in a database and made available online, where users can download it for free. Currently, 71 networks are participating with more than 2800 stations distributed on a global scale and a steadily increasing number of user communities. Long term time series with mainly hourly timestamps from 1952 – up to near-real-time are stored in the database, including daily near-real-time updates. Besides soil moisture in our database are stored other meteorological variables as well (air temperature, soil temperature, precipitation, snow depth, etc.).The ISMN provides benchmark data for several operational services such as ESA CCI Soil Moisture, the Copernicus Climate Change (C3S) and Global Land Service (CGLS), and the online validation tool QA4SM. ISMN data is widely used in a variety of scientific fields (e.g., climate, water, agriculture, disasters, ecosystems, weather, biodiversity, etc).To validate the land surface representations of meteorological forecasting models soil moisture from the ISMN has often been used. The development of various generations of TESSEL models used both in the Integrated Forecasting Systems and reanalysis products of ECMWF, greatly profited from soil moisture and temperature data from the ISMN. Using ISMN data several studies assessed the soil moisture skill of the Weather Research and Forecasting Model (WRF) and assessed the forecast skill or new implementations of numerical weather prediction models.We greatly acknowledge the financial support provided by ESA through various projects: SMOSnet International Soil Moisture Network, IDEAS+, and QA4EO.To ensure a long-term funding for the ISMN operations, several ideas were perused together with ESA. A partner for this task could be found within the International Center for Water Resources and Global Change (ICWRGC) hosted by the German Federal Institute of Hydrology (BfG). In this session, we want to give an overview and future outlook of the ISMN, highlighting its unique features and discuss challenges in supporting the hydrological research community in need of freely available, standardized, and quality-controlled datasets.

The International Soil Moisture Network (ISMN, ) is a unique centralized global and open freely available in-situ soil moisture data hosting facility. Initiated in 2009 as a community effort through international cooperation (ESA, GEWEX, GTN-H, WMO, etc.), with continuous financial support through the European Space Agency (formerly SMOS and IDEAS+ programs, currently QA4EO program), the ISMN is more than ever an essential means for validating and improving global satellite soil moisture products, land surface -, climate- , and hydrological models.Following, building and improving standardized measurement protocols and quality techniques, the network evolved into a widely used, reliable and consistent in-situ data source (surface and sub-surface) collected by a myriad off data organizations on a voluntary basis. 66 networks are participating (status January 2021) with more than 2750 stations distributed on a global scale and a steadily increasing number of user community, > 3200 registered users strong. Time series with hourly timestamps from 1952 – up to near real time are stored in the database and are available through the ISMN web portal for free (), including daily near-real time updates from 6 networks (~ 1000 stations). About 10’000 datasets are available through the web portal and the number of networks and stations covered by the ISMN is still growing as well as most datasets, that are already contained in the database, are continuously being updated.The ISMN evolved in the past decade into a platform of benchmark data for several operational services such as ESA CCI Soil Moisture, the Copernicus Climate Change (C3S), the Copernicus Global Land Service (CGLS), the online validation service Quality Assurance for Soil Moisture (QA4SM) and many more applications, services, products and tools. In general, ISMN data is widely used in a variety of scientific fields with hundreds of studies making use of ISMN data (e.g. climate, water, agriculture, disasters, ecosystems, weather, biodiversity, etc.). In this session, we want to inform ISMN users about the evolution of the ISMN over the past decade, including a description of network and dataset updates and new quality control procedures. Besides, we provide a review of existing literature making use of ISMN data in order to identify current limitations in data availability, functionality and challenges in data usage in order to help shape potential future modes in operation of this unique community- based data repository.