The International Soil Moisture Network: a data hosting facility for global in situ soil moisture measurements

Abstract

In situ measurements of soil moisture are invaluable for calibrating and validating land surface models and satellite-based soil moisture retrievals. In addition, long-term time series of in situ soil moisture measurements themselves can reveal trends in the water cycle related to climate or land cover change. Nevertheless, on a worldwide basis the number of meteorological networks and stations measuring soil moisture, in particular on a continuous basis, is still limited and the data they provide lack standardization of technique and protocol. To overcome many of these limitations, the International Soil Moisture Network (ISMN; <a href="http://www.ipf.tuwien.ac.at/insitu" target="_blank">http://www.ipf.tuwien.ac.at/insitu</a>) was initiated to serve as a centralized data hosting facility where globally available in situ soil moisture measurements from operational networks and validation campaigns are collected, harmonized, and made available to users. Data collecting networks share their soil moisture datasets with the ISMN on a voluntary and no-cost basis. Incoming soil moisture data are automatically transformed into common volumetric soil moisture units and checked for outliers and implausible values. Apart from soil water measurements from different depths, important metadata and meteorological variables (e.g., precipitation and soil temperature) are stored in the database. These will assist the user in correctly interpreting the soil moisture data. The database is queried through a graphical user interface while output of data selected for download is provided according to common standards for data and metadata. Currently (status January 2011), the ISMN contains data of 16 networks and more than 500 stations located in the North America, Europe, Asia, and Australia. The time period spanned by the entire database runs from 1952 until the present, although most datasets have originated during the last decade. The database is rapidly expanding, which means that both the number of stations and the time period covered by the existing stations are still growing. Hence, it will become an increasingly important resource for validating and improving satellite-derived soil moisture products and studying climate related trends. As the ISMN is animated by the scientific community itself, we invite potential networks to enrich the collection by sharing their in situ soil moisture data

Soil Moisture Retrieval Based on GPS Signal Strength Attenuation

“…As reference, in situ time domain reflectometry (TDR) or frequency domain (FD) probes and gravimetric measurements are used as well as model approaches [28][29][30][31][32][33][34]. A comprehensive overview on in situ SM measurements from many different networks around the globe can be obtained in the International Soil Moisture Network (ISMN) [35]. However, the validation sensors, which measure continuously, are typically installed at a certain soil depth and mostly measure the SM only at this certain soil depth without obtaining information from the interface of air and soil.…”

Intercomparison of Soil Moisture Retrievals From In Situ, ASAR, and ECV SM Data Sets Over Different European Sites

“…The predominant land cover type is forest. (Dorigo et al, 2011;Dorigo et al, 2013) at https://ismn.geo.tuwien.ac.at/. At all sites, soil moisture values have been evaluated on a daily basis, by averaging the measurements recorded at 30 minute intervals from 00:00 to 23:30 of the same day as the ASAR and ECV SM acquisition.…”

“…With the availability of these products, it is necessary to validate them using independently derived soil moisture observations obtained through in-situ monitoring, models, or with different satellite sensors (van Doninck et al, 2012;Ochsner et al, 2013;Al-Yaari et al, 2014). In-situ validation has generally been achieved over small temporal and spatial scales but has been significantly advanced since the establishment of the Global Soil Moisture Data Bank (Robock et al, 2000) and the International Soil Moisture Network (ISMN) (Dorigo et al, 2011). For example, Albergel et al (2013c) validated three global soil moisture products using a combination of 196 in-situ stations taken from five different soil moisture networks across the world.…”

Improving soil organic carbon parameterization of land surface model for cold regions in the Northeastern Tibetan Plateau, China

“…However, these retrieval methods perform poorly for estimating soil moisture values in cold regions such as the Tibetan Plateau (TP) area (Chen et al, 2013b;Su et al, 2011;Zeng et al, 2015), and only the value of a few centimeters depth can be derived, which is limited for many applications. Ground measurements are the most accurate soil moisture estimates, and huge efforts have been conducted to establish long-term and largescale soil moisture observation networks in several regions of the world (Dorigo et al, 2011;Yang et al, 2013). Nevertheless, it is still limited and far from sufficient in the TP area, because of the high spatiotemporal variability of soil moisture, the high economic cost and difficulties in practice.…”

“…How to obtain reliable soil moisture products has received increasing interest in recent years and investigators have discussed this issue from ground measurement, remote sensing observation and model simulation aspects (Dorigo et al, 2011;Fares et al, 2013;Romano, 2014;Seneviratne et al, 2010). In the past few decades, several research groups have successfully retrieved soil moisture products from multiple remote sensing sensors (Draper et al, 2009;Entekhabi et al, 2010;Mecklenburg et al, 2012).…”