Description: In 2012, we developed a proof-of-concept system for a new open-path laser absorption spectrometer concept for measuring atmospheric CO2. The measurement approach utilizes high-reliability all-fiber-based, continuous-wave laser technology, along with a unique all-digital lock-in amplifier method that, together, enables simultaneous transmission and reception of multiple fixed wavelengths of light. This new technique, which utilizes very little transmitted energy relative to conventional lidar systems, provides high signal-to-noise (SNR) measurements, even in the presence of a large background signal. This proof-of-concept system, tested in both a laboratory environment and a limited number of field experiments over path lengths of 680 m and 1,600 m, demonstrated SNR values >1,000 for received signals of ~18 picoWatts averaged over 60 s. A SNR of 1,000 is equivalent to a measurement precision of ±0.001 or ~0.4 ppmv. The measurement method is expected to provide new capability for automated monitoring of greenhouse gas at fixed sites, such as carbon sequestration facilities, volcanoes, the short- and long-term assessment of urban plumes, and other similar applications. In addition, this concept enables active measurements of column amounts from a geosynchronous orbit for a network of ground-based receivers/stations that would complement other current and planned space-based measurement capabilities.

Description: A sprinkling experiment was conducted at the geodetic observatory Wettzell (Bavaria, Germany) with the intention to combine classical hydrological field observations of soil moisture with gravity data and electrical resistivity tomography (ERT). The setup consisted of 8 sprinkling units installed around a gravimeter in field enclosure. Artificial rainfall was applied for 6 hours. The sprinkling area of 15 x 15 m was equipped with 3 vertical soil moisture sensor profiles, 1 horizontal soil moisture transect, near-surface soil moisture sensors and 3 ERT profiles. The non-invasive gravity data and the ancillary monitoring data were used to infer water transport processes in the subsurface during the sprinkling experiment. To this end, the gravity data were used to identify the structure and the parameters of a subsurface flow model in an inverse modelling approach by optimizing the simulated gravity response with respect to the observations. The ancillary soil moisture and ERT data were used to evaluate the model outputs in terms of adequacy and dominant subsurface flow processes. Model data cover the following subtopics: • virtual experiments to show the theoretical relationships between subsurface water re-distribution processes and their corresponding gravity responses • an uncertainty analysis of the sprinkling experiment, e.g., with respect to water volumes and their spatial distribution, and the impact on the expected gravity response • inverse modelling to identify dominant subsurface water re-distribution processes • a synthetical model setup based on the ancillary datasets of soil moisture and ERT Monitoring and model output data used for this investigation is provided within this data repository. A detailed description and discussion can be found in Reich et al. (2021). The inverse modelling was carried out using the R-package gravityInf (Reich, 2021).

Description: The data set ": Soil physical and hydraulic properties along two chronosequences of proglacial moraines" consists of several individual files in tabstop delimeted text format. The data set contains soil physical data from two chronosequences of moraines in glacier forefields in the central Alps, Switzerland. Aim of the study was to investigate the impact of age and parent material on soil physical characteristics. At the forefield of the Stone Glacier the moraines developed from silicate parent material (S) and at the forefield of the Griessfirn from calcareous parent material (C). At each forefield disturbed and undisturbed soil samples were collected from four moraines of different ages and porosity, bulk density, particle size distribution, gravel content, ignition loss, retention curves and unsaturated hydraulic conductivity curves were determined. Per moraine, three sampling sites were identified based on the level of vegetation complexity [low, medium, high] (for details on this vegetation classification see Maier et al., 2019). Two sampling locations spaced 3 to 4 m apart were selected per vegetation complexity at each moraine. These different sampling locations are identified in the files as location 1 and 2. Data sets from the moraines developed from silicate parent material are marked with S and data from the moraines with calcareous parent material are marked with C. For the C forefield bulk density, porosity and ignition loss are listed in a single file. For the S location the ignition loss data is listed in a separate file from the bulk density and porosity data. In each file the sample type, the sample volume, the sample number, the moraine age, the sampling depth, and the level of vegetation complexity are provided. The particle size distributions of the fine earth and the gravel content are also listed in individual files. Again, the sample number, moraine age, vegetation complexity, sampling depth and sampling location are noted in the files. For the retention curves and the unsaturated hydraulic conductivity curves, two files exist for each curve and glacier forefield, which are named accordingly with the glacier forefield identification and type of curve. An overview file for each glacier forefield contains a list with the sample number, moraine age, sampling depth, vegetation complexity and sampling location. The other two files per curve contain the lab measurements. For the retention curve data, the sample numbers link the pressure head [cm] values provided in one file to the corresponding volumetric water content [-] values provided in the other file. The same applies to the hydraulic conductivity curve where the sample number now links the unsaturated hydraulic conductivity [cm/h] to the corresponding pressure head [cm].

Description: The data set was collected to identify hydrological processes and their evolution over it time. It consists of several individual files in tabstop delimeted text format. The data set contains the data obtained from deuterium and brilliant blue tracer experiments at two chronosequence studies in the glacier forefield of the Stone Glacier and the Griessfirn in the central Alps, Switzerland. Each chronosequence consisted of four moraines of different ages (from 30 to 13500 years). At each forefield sprinkling experiments with deuterium and dye tracer experiments with blue dye (Brilliant Blue) were conducted on three plots per moraine. The moraines at the forefield of the Stone Glacier developed from siliceous parent material and at the forefield of the Griessfirn from calcareous parent material. Data from the siliceous forefield are marked with (S) and data from the calcareous forefield are marked with (C). The data set consist of soil moisture time series and soil water isotope profiles of the sprinkling experiments with deuterium, as well as trinary images of stained vertical subsurface flow paths from the dye tracer experiment. The individual plots per moraine are distinguished via their position relative to one another on the moraine (left, middle, and right, looking upslope). The plots used for the sprinkling experiments were located in close vicinity to the plots used for the dye tracer experiments. For the sprinkling experiments with deuterium each plot (4m x 6m) per age class was equipped with 6 soil moisture sensors. Three of these sensors were installed as a sensor profile at one side of the plot about one meter downslope from the upper plot boundary. The sensors were installed at 10, 30, and 50 cm soil depth. On the other side of the plot, two sensors were placed in 10 cm depth, one opposite to the sensor profile and the second sensor one meter upslope from the lower plot boundary. The sixth sensor was placed at 10 cm depth in the center of the plot. The plots were irrigated on three consecutive days with three different irrigation intensities and deuterium concentrations. Per forefield, the soil moisture data are listed in one file per age class. The file contains for each plot, the time stamp and the soil moisture values of the 6 sensors.