Project Details
Projekt
Roving & Airborne -- Upscaling soil moisture products with ground- and airborne neutron sensing
Applicants
Dr. Martin Schrön; Dr. Steffen Zacharias
Subject Area
Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
Term
since 2018
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 357874777
In CosmicSense Phase I the research module (RM) "RV: Roving" has been dedicated (i) to the exploration of the potential of mobile cosmic-ray neutron sensing (CRNS) to detect spatial soil moisture patterns, (ii) to develop strategies for the correction and exclusion of unwanted effects, and (iii) to support the Joint Field Campaigns (JFCs) with data acquisition from the field to catchment scales.We found that mobile CRNS is capable of supporting interpolation approaches between stationary networks, of capturing catchment-average wetting and dry-down, and of resolving soil and snow water gradients even on motorways and along train routes. We also invented directional shielding designs to remove local effects or to focus on smaller footprints. Since measurement uncertainty is a crucial factor, we published guidance on the stochastic uncertainty of mobile CRNS and further explored the systematic biases from vegetation and roads. Dedicated lab experiments revealed a significant role of soil properties and provided a first empirical confirmation of the sensing depth. Moreover, we pioneered first preliminary experiments with neutron detectors on a hot-air blimp during the JFC. Despite the recent efforts to establish mobile CRNS for soil moisture mapping, three major challenges remain: (i) Little is known about the correction of influencing factors, such as urban structures, soil properties, land use, and water in snow, biomass, or groups of people; (ii) Rover surveys lack spatial coverage and only represent narrow paths along accessible road networks; and (iii) Car-borne measurements are usually not possible in restricted terrain, such as nature reserves or managed farmland. The overarching objective of the RM "RA: Roving & Airborne" in Phase II is to push the boundaries of the mobile CRNS methodology to facilitate the derivation of reliable soil moisture products at regional scales (1-100 km). To reach that goal, we need to overcome the current limitations mentioned above by striving for the following three objectives. Firstly, we will develop spatial correction approaches based on additional data sets (OpenStreetMap, satellite products, camera images) such that the calibration parameters will be no longer site-specific. Secondly, we aim at upscaling the spatial extent of mobile CRNS measurements by estimating soil moisture and its uncertainty in untouched regions using machine-learning, data fusion, and optimal routing techniques. Thirdly, we will explore the concept and applicability of airborne neutron sensing using neutron simulations as well as measurements with detectors on a gyrocopter and a hot-air blimp.The project relies on the close collaboration with the RMs of Phase II and their contributions to concept development and ground truthing, particularly during the JFCs. In turn, the contributions of "RA: Roving & Airborne" are crucial for the RMs to bridge the scale gap between point and regional data products.
DFG Programme
Research Units
Co-Investigators
Dr.-Ing. Erik Nixdorf; Dr. Hendrik Paasche
