Soil Sampling for Calibration of Cosmic Ray Soil Moisture Sensor, Far North Queensland Rainforest SuperSite, Robson Creek, 2011

Soil sampling was carried out 22 February and 20 September 2011 to calibrate the Cosmic-ray Soil Moisture sensor. 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 soil moisture monitoring 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. CosmOz sensors use cosmic rays originating from outer space to measure average soil moisture over an area of about 40 hectares to a depths of between 10cm in wet soils to 70cm in dry soils. 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. The Robson Ck soil calibration data can be downloaded from http://cosmos.hwr.arizona.edu/Probes/StationDat/073/calib.php