The International Soil Moisture Network: an open source in-situ soil moisture database serving the EO climate community for over a decade

Abstract

The International Soil Moisture Network (ISMN, https://ismn.earth) is a unique centralized global and open freely available in-situ soil moisture data hosting facility (Dorigo et al.,2021: https://hess.copernicus.org/articles/25/5749/2021/). Initiated in 2009 as a community effort through international cooperation (ESA, GEWEX, GTN-H, WMO, etc.), 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. 72 networks are participating (status November 2021) with more than 2800 stations distributed on a global scale and a steadily increasing number of user community, ~ 4000 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 (https://ismn.earth), including daily near-real time updates from 7 networks (~ 1000 stations).

More than 10’000 in-situ soil moisture 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.).

The foundation and continuous development of the ISMN was funded by the European Space Agency (formerly SMOS and IDEAS+ programs, currently QA4EO program). However, it was always clear that financial support from ESA was not realizable on a long term basis. Therefore, several different options for financing ISMN where explored within the last couple of years together with ESA. In January 2021, the German Federal Ministry of Transport and Digital Infrastructure (BMVI: https://www.bmvi.de/EN/Home/home.html) agreed to provide continuous long-term funding for the ISMN operations. Three full time positions are financed at the German Federal Institute for Hydrology (Bafg: https://www.bafg.de/EN/) as well as two full time positions at the connected International Center for Water Resources and Climate Change (ICWRGC https://www.waterandchange.org/en/ - under the auspice of UNESCO and WMO). The transfer of the ISMN operations from Austria (TU Wien) to Germany started in May 2021 and will be finished by end of 2022. This 19 month transfer timeframe is co-financed by ESA and the German Ministry to facilitate a sustainable transfer of knowledge and operations.

In this session, we want to introduce the new hosts (BafG and ICWRGC) and look back at the evolution of the ISMN over the past decade (network and dataset updates, quality procedures, literature overview, and current limitations in data availability – functionality and challenges in data usage). Furthermore, we want to especially look ahead and share new possibilities for the ISMN to serve the EO community for a long time to come.