Assessing the operational applicability of automated measurements of snow water equivalent with low-cost GNSS sensors along a steep elevation gradient in the Eastern Swiss Alps

Project lead: WSL Institute for Snow and Avalanche Reasearch SLF Project partners: SLF, ANavS GmbH, BOKU HyWa Project funding (for Swiss partner): MeteoSwiss / Swiss GCOS Snow water equivalent (SWE) is a key property of the seasonal snow cover as the water stored in the snowpack is a crucial contribution to the hydrological cycle in mountain areas. Estimating the spatial distribution and temporal evolution of SWE in mountainous terrain is currently considered as one of the most important unsolved problems in snow hydrology. For assessing the snow mass stored in the mountain snow cover several methods exist. These in-clude interpolating between on-the-ground point measurements, distributed physically-based snow cover modelling and remote sensing. The latter seems the ideal candidate to monitor the spatial distri-bution of SWE and its temporal evolution. However, current operational satellite SWE retrievals pro-vide estimates at about 25-km resolution. Hence they are of limited value for mountain areas with complex topography. On the other hand, physical modelling allows for much higher resolution (1 km). Yet, best results with distributed modeling are obtained when observations of SWE are assimilated. Therefore, on-the-ground measurements are still essential, but are scarce and mostly non-continuous, or otherwise costly. However, recently a novel measurement technique has been developed and pre-liminary results are promising. This snow measurement technique is based on the combination of GNSS carrier phases indicating signal time delay within the snowpack and GNSS signals strength information indicating signal attenuation. Our goal is therefore to apply this emerging observation method for deriving SWE at high temporal resolution with reasonable costs, further develop its snow algorithm and evaluate its performance along a steep elevation gradient (from 815 to 2540 m asl.) where very different snow conditions pre-vail. This will ultimately allow assessing whether the new method is suited for operational use within the Swiss observational network for SWE.