Abstract
Abstract. Besides its important role in the energy and water balance at the soil–atmosphere interface, soil moisture can be a particular important factor in mountain environments since it influences the amount of freezing and thawing in the subsurface and can affect the stability of slopes. In spite of its importance, the technical challenges and its strong spatial variability usually prevents soil moisture from being measured operationally at high and/or middle altitudes. This study describes the new Swiss soil moisture monitoring network SOMOMOUNT (soil moisture in mountainous terrain) launched in 2013. It consists of six entirely automated soil moisture stations distributed along an altitudinal gradient between the Jura Mountains and the Swiss Alps, ranging from 1205 to 3410 m a.s.l. in elevation. In addition to the standard instrumentation comprising frequency domain sensor and time domain reflectometry (TDR) sensors along vertical profiles, soil probes and meteorological data are available at each station. In this contribution we present a detailed description of the SOMOMOUNT instrumentation and calibration procedures. Additionally, the liquid soil moisture (LSM) data collected during the first 3 years of the project are discussed with regard to their soil type and climate dependency as well as their altitudinal distribution. The observed elevation dependency of LSM is found to be non-linear, with an increase of the mean annual values up to ∼ 2000 m a.s.l. followed by a decreasing trend towards higher elevations. This altitude threshold marks the change between precipitation-/evaporation-controlled and frost-affected LSM regimes. The former is characterized by high LSM throughout the year and minimum values in summer, whereas the latter typically exhibits long-lasting winter minimum LSM values and high variability during the summer.
Highlights
Soil moisture is a key factor controlling the energy and water exchange processes at the soil–atmosphere interface as well as the physical properties of the subsurface
At 30 cm depth two SMT100 sensors have been installed in parallel to investigate potential instrumental drift over longer time periods
At FRE, DRE, MLS and GFU the correlation between the liquid soil moisture (LSM) measured by the two sensors is found to be satisfactory
Summary
Soil moisture is a key factor controlling the energy and water exchange processes at the soil–atmosphere interface as well as the physical properties of the subsurface. The latter include important properties for the thermal regime such as heat capacity and thermal conductivity (for a review see, e.g. Seneviratne et al, 2010). Even though the number of soil moisture networks is globally increasing, it is still far from being standardized, coordinated or spatially representative. In the interest of representativeness for large-scale studies and due to easy implementation most of the current monitoring networks are located at middle to low elevation.
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