Abstract
Abstract. A cosmic-ray soil moisture probe is usually calibrated locally using soil samples collected within its support volume. But such calibration may be difficult or impractical, for example when soil contains stones, in presence of bedrock outcrops, in urban environments, or when the probe is used as a rover. Here we use the neutron transport code MCNPx with observed soil chemistries and pore water distribution to derive a universal calibration function that can be used in such environments. Reasonable estimates of pore water content can be made from neutron intensity measurements and by using measurements of the other hydrogen pools (water vapor, soil lattice water, soil organic carbon, and biomass). Comparisons with independent soil moisture measurements at one cosmic-ray probe site and, separately, at 35 sites, show that the universal calibration function explains more than 79% of the total variability within each dataset, permitting accurate isolation of the soil moisture signal from the measured neutron intensity signal. In addition the framework allows for any of the other hydrogen pools to be separated from the neutron intensity measurements, which may be useful for estimating changes in biomass, biomass water, or exchangeable water in complex environments.
Highlights
Understanding the exchange of water between the land surface and atmosphere is critical for accurate initialization of general circulation models (Koster et al, 2004; Wang et al, 2006), understanding energy and water fluxes (Seneviratne et al, 2010), and making short-term weather predictions
Fifty probes have been deployed around the continental USA as part of the COsmic-ray Soil Moisture Observing System (COSMOS) (Zreda et al, 2012; data available at http://cosmos.hwr.arizona.edu/), and other networks are being installed elsewhere
Franz et al.: A universal calibration function for determination of soil moisture water is still exchanged between the land surface and atmosphere at these sites, and observations of area-average moisture are necessary to understand the transfer of mass, momentum, and energy in these systems
Summary
Understanding the exchange of water between the land surface and atmosphere is critical for accurate initialization of general circulation models (Koster et al, 2004; Wang et al, 2006), understanding energy and water fluxes (Seneviratne et al, 2010), and making short-term weather predictions. Franz et al.: A universal calibration function for determination of soil moisture water is still exchanged between the land surface and atmosphere at these sites, and observations of area-average moisture are necessary to understand the transfer of mass, momentum, and energy in these systems. Such observations may be possible with the aid of a universal calibration function. We develop a universal calibration function for the cosmic-ray neutron probe It accounts for several sources of time-varying hydrogen signals that may be present in the probe’s support volume in order to expand the potential use of the probe to hitherto difficult sites and novel applications. We test the validity of the function by using observed neutron data from 35 COSMOS sites (where we have full calibration datasets) with a wide range of conditions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
