Brief description
The Australian cosmic-ray soil moisture monitoring network was first established in 2010 to provide Australian and global researchers with spatially distributed intermediate scale soil moisture observations. A cosmic-ray sensor (CRS) provides continuous estimates of soil moisture over an area of approximately 30 hectares by measuring naturally generated fast neutrons (energy 10–1000 eV) that are produced by cosmic rays passing through the Earth’s atmosphere. The neutron intensity above the land surface is inversely correlated with soil moisture as it responds to the hydrogen contained in the soil and to a lesser degree to plant and soil carbon compounds. The cosmic-ray technique is also passive, non-contact, and is largely insensitive to bulk density, surface roughness, the physical state of water, and soil texture. The scale of CRS measurements fills the void between point scale sensor measurements and large scale satellite observations. The depth of measurements varies with the moisture content of the soil but is typically between 10-30 cm. The depth of observations is reported as ‘effective depth’.The CosmOz network is expanding as new sensors are added over time. The initial network was funded by CSIRO Land and Water but more recently TERN has funded work to maintain the network add new sensors and deliver data more efficiently. The standard CRS installation includes; a cosmic-ray neutron tube, a rain gauge (2m high), temperature and humidity sensors, and an atmospheric pressure sensor. Measures of all parameters are reported at an hourly interval. Each CRS requires an in-field calibration across the footprint of measurements to convert neutron counts to soil moisture content. The calibration includes collection of soil samples for bulk density, lattice water content and soil organic carbon.
The Australia CosmOz network consists of 19 stations. The extent of the network and available data can be seen at the CosmOz network web page: https://cosmoz.csiro.au. The data is also accessible from the TERN Cosmoz REST API.
The calibration and correction procedures used by the network are described by Hawdon et al. 2014 .
Notes
Supplemental InformationNeutron intensity data for neutron intensity corrections are supplied by the Neutron Monitor Database (https://www.nmdb.eu/)
Lineage
Progress Code: onGoingNotes
CreditWe at TERN acknowledge the Traditional Owners and Custodians throughout Australia, New Zealand and all nations. We honour their profound connections to land, water, biodiversity and culture and pay our respects to their Elders past, present and emerging.
This work was jointly funded by the Terrestrial Ecosystem Research Network (TERN), an Australian Government National Collaborative Research Infrastructure Strategy (NCRIS) project, and the Queensland Government Research Infrastructure Co-investment Fund (RICF).
The purpose of the data from the CosmOz network is to provide long-term, intermediate-scale soil moisture estimates at an hourly time-interval across different environments in Australia.
Data Quality Assessment Scope
local :
dataset
The cosmic-ray sensor is calibrated with collection of soil cores in the field. In total 72 soil cores are collected from location at different radial distances from the sensor and at different depth in the profile. Data is delivered with 5 levels of processing to maintain data integrity. These levels are: 'Raw Data' - data as it comes straight from the station, 'Level 1' - data with high and low neutron counts flagged and low battery flagged, 'Level 2' - data with corrections for atmospheric humidity, atmospheric pressure and incoming neutron intensity, 'Level 3' - calculated soil moisture content, depth of measurement and rainfall, and 'Level 4' - final high quality data including a 7-hour moving average. Refer to <a href="https://doi.org/10.1002/2013WR015138">Hawdon et al. 2014 </a>.
Data Quality Assessment Result
local :
Quality Result
Measurement precision increases with the number of neutron counts as neutron intensity follows Poisson statistics. The longer the averaging the less the uncertainty in soil moisture observations. Modelling suggests that uncertainty is typically in the order of 0.03 m^3/m^3.
Created: 2020-03-19
Issued: 2021-10-25
Modified: 2025-12-15
Data time period: 2011-10-28
text: The CosmOz network extends across Australia. See cosmoz.csiro.au for sensor locations.
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Point-of-truth metadata URL- URI : geonetwork.tern.org.au/geonetwork/srv/eng/catalog.search#/metadata/3567cff4-4a73-439e-a1b4-d30caf3c8959
- global : 3567cff4-4a73-439e-a1b4-d30caf3c8959
