CosmOz - The Australian Cosmic-ray Soil Moisture Sensor Network

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 .澳大利亚宇宙射线土壤湿度监测网络始建于2010年，旨在为澳大利亚及全球科研人员提供空间分布式的中尺度土壤湿度观测数据。宇宙射线传感器 (cosmic-ray sensor, CRS) 通过测量穿过地球大气层的宇宙射线所产生的天然快中子（能量范围10–1000电子伏特），可对约30公顷范围内的土壤湿度进行连续估算。地表上方的中子强度与土壤湿度呈负相关关系，因为中子强度会响应土壤中含有的氢元素，同时在较小程度上响应植物与土壤中的碳化合物。该宇宙射线探测技术同时具备被动、非接触的特性，且基本不受土壤容重、地表粗糙度、水的物理状态以及土壤质地的影响。宇宙射线传感器的观测尺度填补了点尺度传感器观测与大尺度卫星观测之间的空白。探测深度随土壤湿度含量变化，通常介于10至30厘米之间，该观测深度以"有效深度"进行标注报告。 CosmOz网络正随着新传感器的陆续部署而不断扩容。该网络最初由CSIRO Land and Water资助，近期则由TERN资助开展网络维护、新增传感器部署及更高效的数据交付工作。标准的CRS部署套件包含：宇宙射线中子管、2米高雨量计、温湿度传感器以及大气压力传感器。所有参数的观测数据均按小时间隔进行记录上报。每台CRS均需在其观测覆盖区内开展野外校准工作，以将中子计数转换为土壤湿度含量。校准工作需采集土壤样本，以测定土壤容重、晶格水含量以及土壤有机碳含量。 澳大利亚CosmOz网络共计19个监测站。该网络的覆盖范围与可用数据集可通过CosmOz官方网页https://cosmoz.csiro.au查询，数据也可通过TERN Cosmoz REST API获取。 该网络所采用的校准与校正流程详见Hawdon等人2014年发表的研究成果。