Soil Moisture Content, Cosmic Ray Soil Moisture Sensor, Far North Queensland Rainforest SuperSite, Robson Creek, 2011

A cosmic ray soil moisture sensor was installed at Robson Creek node of the FNQ Rainforest Supersite on 28 Oct 2010 by the Australian Cosmic Ray Soil Moisture Monitoring Network (CosmOz; http://www.ermt.csiro.au/html/cosmoz.html). CosmOz represents just one of a growing number of networks around the World. Other networks are found in USA, Germany, and the UK with other projects adopting the technology in South America, Africa and Europe.

These sensors use cosmic rays originating from outer space to measure average soil moisture over an area of about 40 hectares to a depth up to 90 cm. The system measures fast neutrons that are produced from interactions of cosmic rays with the atmosphere and top few meters of soil. The intensity of these neutrons are moderated largely by water molecules in the soil. The number of neutrons counted over a period of time is inversely proportional to the amount of water in the soil. To estimate volumetric water content, each system is calibrated against soil samples that are collected from dry and wet moisture regimes using a standard protocol.

Data is collected every 60 min and uploaded to data portal infrastructure which is maintained by the University of Arizona. This infrastructure and associated web interface were established as part of the US based Cosmic-ray Soil Moisture Observation System (COSMOS, http://cosmos.hwr.arizona.edu/). Collaboration between Australian and US researchers has facilitated a data hosting agreement which has now resulted in a growing international data portal for delivering and processing data from cosmic-ray probes.

The Robson Ck data can be downloaded from http://cosmos.hwr.arizona.edu/Probes/StationDat/073/index.php