Scientific evolution of the International Soil Moisture Network: Past, present, and future developments in support of soil moisture validation and applications

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).