Simultaneous measurement of soil moisture and biomass pattern with aCRNS rover

While "classical" stationary cosmic-ray neutron sensors (CRNS) measure the temporal variability of soil moistureat the field scale, the mobile application of CRNS (CRNS rover) enables to capture the spatial variability of soilmoisture across larger areas or transects. The CRNS rover consists of two components - a vehicle and a set oflarge neutron counters. The detectors need to have higher count rates in order to achieve sufficient sensitivity forvery short recording periods (e.g. 1 min). To date, only few experiments have been conducted with the CRNSrover over a wide range of different land-use types. Such experiments are needed as the neutron intensity is notonly sensitive to soil moisture, but also to all other additional sources of hydrogen (e.g. biomass), which needto be corrected for. Interestingly, the ratio between thermal and fast neutron intensity (Nr) seems to be a verygood indicator for vegetation and can be used for the correction of aboveground biomass effects on soil moisturemeasurements with cosmic-ray neutrons. This enables the possibility for “on-the-fly” correction of soil moisturemeasurements without the need for laborious local biomass sampling during CRNS roving campaigns. In addition,using the Nr-information from CRNS roving would allow for the simultaneous measurements of soil moisture andbiomass pattern at the regional scale.In this contribution, we present results from a recent roving campaign at the TERENO test site Selhausen(about 1 km2). We used a new cosmic rover with 9 detectors and a total sensitivity of approx. 1350 counts perminute, which enables higher speed and larger coverage compared to other roving systems. In addition, thedetectors can be modified to measure either thermal or fast neutron intensity measurements. During the two-weekcampaign a large set of different field sites with various vegetation covers has been repeatedly monitored. Thepreliminary results show that CRNS rover was able to capture the general soil moisture pattern and that theNr-information could be used to improve the soil moisture estimation. In future we hope to enable the simultaneousmeasurements of soil moisture and biomass patterns at the regional scale with Nr-information from CRNS roving