Neutrons on Rails: Transregional Monitoring of Soil Moisture and Snow Water Equivalent

Large-scale measurements of the spatial distribution of water content in soils and snow are challenging for state-of-the-art hydrogeophysical methods. Cosmic-ray neutron sensing (CRNS) is a noninvasive technology that has the potential to bridge the scale gap between conventional in situ sensors and remote sensing products in both, horizontal and vertical domains. In this study, we explore the feasibility and potential of estimating water content in soils and snow with neutron detectors in moving trains. Theoretical considerations quantify the stochastic measurement uncertainty as a function of water content, altitude, resolution, and detector efficiency. Numerical experiments demonstrate that the sensitivity of measured water content is almost unperturbed by train materials. Finally, three distinct real-world experiments provide a proof of concept on short and long-range tracks. With our results a transregional observational soil moisture product becomes a realistic vision within the next years.

Automated summary

The study investigates the feasibility of estimating water content in soils and snow using neutron detectors on moving trains. Theoretical considerations quantify measurement uncertainty, while numerical experiments show that the sensitivity of measured water content is not affected by train materials. Real-world experiments on short and long-range tracks provide proof of concept for transregional observational soil moisture products in the future.