Technical note: Towards a paradigm change in observing soil water content via cosmic-ray neutron sensing

Abstract. Observing soil moisture via cosmic-ray neutron sensing has seen a rapid methodological development and expansion during the last decade. However, to foster its application some change in perspective may be useful. We reformulate the most common calibration equation used when working with CRNS data, the Desilets equation, and provide a simple and insightful form. This leads us also to a new option for calibration of CRNS time series without any local sampling of soil moisture, and also without knowledge on CRNS detector sensitivity. At the same time it delivers the basis for a quantitative expression on how heterogeneities in the footprint contribute to the CRNS-derived soil moisture as well as why statistical errors in practice may be larger than assumed usually. Finally, we suggest to also define the area (and volume) represented by the CNRS observation in a more pragmatic way and complement it by indicating needs for better standardization.