Improving temporal and spatial estimates of solid precipitation and accumulation in high mountain regions (High-SPA)

Precipitation estimates in high mountain regions are fundamental for the understanding of many key processes in research domains like glaciology, hydrology and/or climatology. In the European Alps, a relatively dense observation network and gridded climatologies are available. Nevertheless, the accuracy of these data at high altitudes is low due to the lack of reliable measurements of precipitation and snow accumulation. At the same time, a large number of glaciers are situated at these high altitudes storing temporally high amounts of precipitation. They are among the most important cryospheric components and represent a valuable indicator of climate change. The annual mass changes of glaciers are mainly dictated by the quantity of accumulated snow and by summer air temperature. The scarcity and the considerable uncertainties of precipitation estimates in high mountain regions are therefore a major drawback for enhancing our understanding of climate-cryospheric processes and limits the reduction of uncertainties in related climate impacts studies. This project aims at tackling this research need by providing combined methods, which are particularly suitable for measuring and modeling solid precipitation and snow accumulation in complex high mountain topography.

Research aims

• Assess the application of a cosmic ray sensor (CRS) for daily observations of the snow water equivalent. The CRS is installed on the glacier ice and is buried by the snow pack during the winter season.
• Assess the performance of operational weather radar composites provided by MeteoSwiss (CombiPrecip) to estimate the end-of-season winter mass balance. The estimates of snow accumulation from the cumulative precipitation are validated with in situ manual measurements on several glacier. These measurements are provided by the Glacier Monitoring network of Switzerland (GLAMOS).
• Assess the performance of COSMO-1 analysis data for inferring the end-of-season winter mass balance on several glaciers. Compare the performance of COSMO-1 to CombiPrecip.

Methods

The cosmic ray sensor counts the number of fast neutrons from secondary cascades of cosmic rays. Hydrogen atoms effectively moderate these fast neutrons. Therefore, hydrogen atoms and fast neutrons are negatively correlated. The deeper the snowpack, the fewer fast neutrons arrive at the device. Additionally, the bulk snow density is calculated with the autonomous SWE measurements and snow depth measurements (SR50A). For validation, we compare the autonomous measurements to manual in-situ measurements with snow probings (snow depth) and snow pits (SWE, snow density).

Study area

Our study sites are located in the Swiss Alps. We maintain an automatic weather station (snow depth, air temperature, air pressure, relative humidity, wind speed, wind direction and radiation) with a CRS on the Glacier de la Plaine Morte (since October 2016) and the Findelengletscher (Ocober 2018).