The International Soil Moisture Network: an open-source data hosting facility in support of hydrological research
Authors: Himmelbauer Irene , Aberer Daniel , Schremmer Lukas , Petrakovic Ivana , Zappa Luca , Xaver Angelika , Dorigo Wouter , Goryl Philippe , Sabia Roberto 
Published: March 2020

&lt;p&gt;&lt;span&gt;The International Soil Moisture Network (ISMN, &lt;/span&gt;&lt;span&gt;&lt;/span&gt;&lt;span&gt;) is an international cooperation to establish and maintain an open-source global data hosting facility, providing in-situ soil moisture data as well as accompanying soil variables. This database is an essential means for validating and improving global satellite soil moisture products as well as land surface -, climate- , and hydrological models.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;For hydrological validation, the quality of used in-situ data is essential. The various independent local and regional in situ networks often do not follow standardized measurement techniques or protocols, collect their data in different units, at different depths and at various sampling rates. Besides, quality control is rarely applied and accessing the data is often not easy or feasible.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;The ISMN was created to address the above-mentioned issues. Within the ISMN, in situ soil moisture measurements (surface and sub-surface) 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. &lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Since its establishment in 2009 and with continuous financial support through the European Space Agency (ESA), the ISMN evolved into a widely used in situ data source growing continuously (in terms of data volume and users). Historic measurements starting in 1952 up to near&amp;#8211;real time are available through the ISMN web portal. Currently, the ISMN consists of 60 networks with more than 2500 stations spread all over the globe. With a &lt;/span&gt;&lt;span&gt;&lt;span&gt;steadily growing user community more than 3200 registered users strong&lt;/span&gt;&lt;/span&gt;&lt;span&gt; the value of the ISMN as a well-established and rich source of in situ soil moisture observations is well recognized. In fact, the ISMN is widely used in variety of scientific fields (e.g. climate, water, agriculture, disasters, ecosystems, weather, biodiversity, etc.). &lt;/span&gt;&lt;/p&gt;&lt;p&gt; &lt;span&gt;Our partner networks range from networks with a handful of stations to networks that are composed of over 400 sites, are supported with half yearly provider reports on statistical data about their network (e.g.: data download statistic, flagging statistic, etc.). &lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;About 10&amp;#8217;000 datasets are available through the web portal. However, the spatial coverage of in situ observations still needs to be improved. For example, in Africa and South America only sparse data are available. Innovative ideas, such as the inclusion of soil moisture data from low cost sensors (GROW observatory ) collected by citizen scientists, holds the potential of closing this gap, thus providing new information and knowledge.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;In this session , we want to give an overview of the ISMN, its unique features and its support of data provider, who are willing to openly share their data, as well as hydrological researcher in need of freely available datasets.&lt;/span&gt;&lt;/p&gt;