KITcube is the highly sophisticated, integrated atmospheric observation system of the Institute for Meteorology and Climate Research, Troposphere Research Division (IMK-TRO). KITcube consists of a mobile system for worldwide deployment and a stationary observatory for continuous monitoring.

The mobile KITcube combines high-resolution measurements of scanning remote sensing systems (e.g. wind lidar, X-band precipitation radar, humidity and temperature profilers, sun photometers, water vapour and cloud camera systems, and many more) with classical in situ instruments on measurement masts and on weather balloons (local measurements). Fully coordinated scans of the systems make the KITcube a very well suited observation system for studies of thunderstorms, atmospheric convection, clouds and precipitation. The mobile KITcube main site during the Swabian MOSES measurement campaign is located in Rottenburg am Neckar, the X-band precipitation radar is installed in Nürtingen.

The stationary KITcube at KIT Campus North in Eggenstein-Leopoldshafen north of Karlsruhe consists, among other things, of the 200 meters high meteorology mast, which has been measuring air temperature, humidity, wind and turbulence in continuous operation since 1972, and a modern C-band precipitation radar. The stationary KITcube is part of the AERONET measurement network, providing data for the station "Karlsruhe". The mobile KITcube can be used as additional temporary station during measurement campaigns such as Swabian MOSES ("KITcube_Rottenburg"). Thus, both contribute to a worldwide database of aerosol and radiation measurements.

Balloon soundings in the atmosphere

The higher atmospheric layers can be measured preferably with helium-filled weather balloons. Various measuring instruments are attached to these balloons, which then measure various parameters as the balloon rises (and also as it sinks later). Depending on their size, the balloons rise to an altitude of 20 to 35 kilometers and thus fly much higher than airplanes. After the balloon bursts, the descent begins, during which a parachute is usually used to slow the descent. On the one hand, this prevents damage, and on the other hand, it allows measurements to be made under controlled conditions even during descent.

In the simplest case, a so-called radiosonde is attached to a weather balloon. This device measures temperature, humidity, air pressure and position information (GPS) and sends the information by radio to the ground station. In addition, it is possible to hang other instruments on the weather balloon besides the radiosonde. These are then, for example, an ozone instrument, with which the ozone layer, particularly in the stratosphere can be measured, or a precise hygrometer, with which the low water vapor concentration at the transition from the troposphere to the stratosphere (tropopause) at an altitude of about 12 kilometers can be precisely determined. Depending on the situation, a particle measuring instrument is also used to precisely locate cloud droplets, ice crystals or dust particles in the atmosphere.

As part of the Swabian MOSES 2023 measurement campaign, balloon soundings will be carried out at two locations: at the main site in Villingen-Schwenningen and in Alsace, France. In Villingen-Schwenningen, the weather balloons are filled manually and allowed to rise; in Alsace, there is an autolauncher. This autolauncher (Vaisala Autosonde AS41) performs balloon soundings fully automatically controlled remotely.

Measuring probes

During flood events, hydrological and water chemical parameters change within a very short time. In order to record these dynamics, nine continuously measuring probes are installed at three locations in the rivers Ammer, Steinlach and Goldersbach. For example, the CTD turbidity probe (see photo) measures electrical conductivity, water temperature, water level and turbidity. Other probes measure the parameters oxygen, pH and chlorophyll. A third probe developed by the UFZ outputs information on dissolved organic carbon and nitrate levels.

ISCO Autosampler

For all water quality parameters that cannot be measured with probes, automatic samplers, so-called autosamplers from ISCO (Model 3700; see photo), are used. An integrated pump draws water samples at predefined time intervals and fills glass bottles located inside the device. Autosamplers generate composite water samples, by e.g. pumping a volume of 250 milliliters into the same 1-liter bottle four times per hour (every 15 minutes), that reflect changes in water chemistry over time. Since river water is usually very turbid during floods, suspended solids are also sampled. In addition to automatically generated composite water samples, manual sampling will be conducted at some sites, primarily to decipher pollutant inputs from specific sources such as urban areas or road runoff, and to investigate the extent to which rivers are sources of greenhouse gases in relation to the degree of land use in the catchment (see research objectives).

Chemical and bioanalytical methods

Samples collected during rain events will be processed in the laboratory of the Geo- and Environmental Research Centre of the University of Tübingen. Using instrumental analysis, complex chemical mixtures in the water will then be identified and their toxic effects determined using bioanalytical methods. In this process, pollutants dissolved in water and chemicals bound to particles are separated from each other by filtration and examined separately. Analyses at the University of Tübingen include nutrients such as nitrate, particle size distribution and the determination of dissolved carbon.

At the UFZ Department of Cell Toxicology in Leipzig, the high-throughput platform CITEPro (Chemicals in the Environment Profiler) is used to analyse the effects of chemical mixtures, using cell-based in vitro bioassays. In addition, organic chemicals are identified and their concentrations determined using high-resolution mass spectrometry (HR-MS). At the UFZ in Magdeburg, trace elements such as zinc, copper, iron and gadolinium are analysed, which can be used as indicators for certain substance input pathways, e.g. from urban areas. In addition, at the UFZ Leipzig, ultra-high resolution mass spectrometry (FT-ICR-MS) is used to characterise dissolved organic material from various sources in the catchment area in more detail. At the KIT branch in Garmisch-Partenkirchen, analyses of greenhouse gases such as nitrous oxide are performed.

Authors: Dr. Clarissa Glaser, University of Tübingen; Dr. Stephanie Spahr, University of Tübingen/IGB Berlin & Dr. PD Ralf Kiese, KIT

Fluctuations of the atmospheric ground pressure are an expression of the weather pattern and are also recorded by many amateur meteorologists. In addition to the slow fluctuations recorded by a barometer, thunderstorm cells, for example, can also generate sudden pressure fluctuations. These pressure fluctuations are sources of infrasound waves that can propagate in the atmosphere over long distances. The infrasound range adjoins the audible range at lower frequencies; the transition between the infrasound range and the acoustic sound range is about 20 hertz (audible range spans about 20 to 20,000 hertz, depending on age and volume).

The operated campaign sensor detects pressure fluctuations in the frequency range from about 0.02 to 100 Hertz, and can therefore detect infrasonic waves and acoustic waves in the lower audible range. A sensitive differential pressure sensor is used for detection (Sensirion SPD816-125Pa), which detects the pressure difference between a sealed reference vessel (a glass vessel with a volume of 5 liters) and the environment. To detect the pressure difference, the sensor allows a small flow of air driven by the pressure difference between the reference volume and the outside air through a narrow channel. A heat source is located in the duct, and the air temperature is measured on both sides of the source. The flow velocity can be derived from the temperature difference and from this, finally, the sought pressure difference.

The figure on the right shows the sensor: the reference vessel is wrapped in thermal insulation to prevent rapid temperature fluctuations of the reference - which would also simulate pressure fluctuations. The actual sensor element is located in the metal housing above the reference vessel. The data is automatically recorded with the help of a notebook and transferred to the campaign's data server via an LTE connection.

Only a few measurements have been performed so far to investigate the infrasound signals of convective events. In the Swabian MOSES campaign, infrasound measurements will be combined with the long-range diagnostics of the KITcube instruments to gain additional information on the flow events in a thunderstorm cell.

Author: Dr. Frank Hase, IMK-ASF

MoLEAF (Mobile Land-Ecosystem-Atmosphere Flux) is a mobile measuring system that is used to measure the fluxes of energy and matter between the land surface and the atmosphere. This system consists of a trailer mast, which is equipped with various measuring instruments and can be pneumatically extended to a height of 30 metres. The second important component of the MoLEAF system is a mobile laboratory cabin that can be transported on a pickup truck and can dropped at the measurement site. It contains a computer workstation, the power supply for the measurement system, and the internet connection. Together this enables the rapid deployment of the measuring system in the event of extreme weather events with a short warning time and self-sufficient operation on site. Thus, measurements can start within a few hours after arrival at the site.

The central measuring unit of the MoLEAF is a so-called eddy covariance system, which is based on a common and widely used method for measuring and calculating vertical turbulent fluxes within atmospheric boundary layers. The eddy covariance method analyzes high-frequency wind and scalar atmospheric data series, gases, energy, and momentum to determine the vertical fluxes of these quantities. This statistical method in commonly used in meteorology and other applications (micrometeorology, oceanography, hydrology, agricultural sciences, industrial and regulatory applications, etc.) to determine the exchange fluxes of trace gases over natural ecosystems and agricultural fields and to quantify gas emission rates. The method is also widely used to verify and calibrate climate and weather models, complex biogeochemical and ecological models, and remote sensing estimates from satellites and aircraft. Due to its mathematic complexity the covariance method requires considerable care in setting up and processing data.

Via the eddy covariance system the exchange of sensible heat, i.e. the energy used to heat the air, the exchange of CO₂, and evaporation can be determined. In addition, the MoLEAF has measuring instruments for recording the radiation balance, which is composed of short-wave and long-wave radiation, for determining the soil heat flux, the soil water content, the air temperature and the air humidity. Wind speed and direction are also recorded. All measurements are continuously and automatically operated during measrement campaing, with a high temporal resolution (0.1 seconds for turbulent quantities and 1 minute for non-turbulent quantities) and can also be monitored remotely via the Internet.

Author: Dr. Matthias Mauder, IMK-IFU

A network of soil moisture sensors enables the continuous determination of soil moisture and soil temperature at different depths. The mobile devices used in the campaign consist of individual sensor nodes, to each of which six soil moisture sensors are connected. The sensors are installed in pairs, so the soil moisture and soil temperature can be determined at each location at three different depths. The measured data is transferred to a database via mobile radio and visualized.

The soil moisture sensors work according to the TDT principle (Time Domain Transmission). The principle is based on the influence of the dielectric properties of the soil on the propagation speed of an electromagnetic signal that is transmitted as a pulse to the sensors. Water is characterized by high dielectricity compared to dry soil. A high water content in the soil and thus a high dielectricity slows down the propagation speed of the electromagnetic signal. With the inclusion of other parameters such as soil temperature, the soil moisture can be determined from the propagation velocity.

Why are these measurements important? Soil moisture is an important state variable of natural soils, which is not only of great importance for agriculture (see research objectives). Due to the pronounced heterogeneity and complexity of soils, soil moisture is also characterized by high temporal and spatial variability. Single measurements often cannot adequately represent such changes due to their principle. Wireless sensor networks make it possible to investigate the temporal and spatial dynamics of soil moisture.

More infomation about the activity within Swabian MOSES as well as live data can be found here

Authors: Matteo Bauckholt, Prof. Dr. Peter Dietrich, UFZ

Precipitation measurements with radars such as the KITcube X-band radar provide very high spatial and temporal resolution information that cannot be achieved with a ground network of precipitation gauges. However, they also suffer from typical measurement errors. These are attempted to be minimized by taking advantage of the (relatively few) measurements on the ground to enrich the radar measurement.

For Swabian MOSES, a network of 23 optical distrometers (parsivels) is being set up for the first time. While conventional rain gauges only provide information on the amount of precipitation that has fallen, the use of distrometers also provides information on the composition of the precipitation according to size and precipitation type. Exactly this information can also be estimated from the measurements of the polarimetric KITcube X-band radar. By comparison with the distrometers distributed throughout the measurement area, the radar-based information can be verified and improved by calibration (also of the polarimetric measured quantities).

Author: Dr. Jan Handwerker, IMK-TRO

Despite the massive damage caused by severe hail events, especially in the Swabian MOSES study area, hail is not measured directly at the many weather stations in Germany. However, the size distributions of the hailstones, the so-called spectra, are relevant for several applications. Precipitation radars, for example, also measure hail in principle, but they only provide a total signal (or several signals in the case of modern dual-pole instruments) in the atmosphere at an altitude of about 1 kilometer.

Observed spectra can be used to improve conversion methods of the radar signal to hail on the ground. The hail spectra are also critical for damage to buildings, vehicles, and agricultural crops. Therefore, they are needed for the most accurate calculation of hail damage and hail risk. Finally, long-term measurements of the hailstones can be used to determine possible trends caused by climate change.

The newly developed measuring device HailSens is capable of measuring hail spectra with high temporal resolution. When a hailstone strikes the receiving surface, the surface is set into vibration, which is then detected by a piezoelectric microphone mounted below the receiving surface. From this, it can then be determined how many hailstones hit and how large they are. Each impact of a hailstone is registered and automatically sent to a server. There, the data is then available in almost real time.

As part of the Swabian MOSES field measurement campaign, a total of 10 hail measuring devices have been installed - precisely at the locations where, according to the IMK 's radar analyses, hail occurs most frequently.

Author: Prof. Dr. Michael Kunz, IMK-TRO

The measurement of wind as a vectorial quantity (wind speed and direction) with strong spatial and temporal variability poses great challenges to the measurement concept and measurement technology, but is of fundamental importance for understanding the energy and material balance of the atmosphere.

Doppler lidar instruments determine the velocity of scatterers (aerosol particles) moving with the wind based on the Doppler effect along a laser beam up to distances of 10 kilometers. To determine the wind vector as well as vertical and horizontal sections, the laser beam is directed in different directions into the half-space above the instrument via a controllable mirror system (scanner). A special added value arises from the combined and synchronized use of the instruments, whereby either small-scale (e.g. in valleys) high-resolution flow patterns can be measured or, as in the case of the Swabian MOSES measurement campaign, larger-scale flow characteristics can be measured in more extensive study areas, which means that, for example, the advection and flow convergence important for thunderstorm formation can be determined (see research objectives).

Within the framework of Swabian MOSES, the IMK-TRO operates Doppler lidar devices with data transmission in near real time to determine the wind profile up to heights of 3 kilometers at a total of 7 sites in the study area between the eastern Black Forest, Neckar Valley and western Swabian Alb. These will be complemented by airborne scanning Doppler lidar in June and July (see research aircraft). Instruments of the project partners IMK-IFU and University of Hohenheim complement the network with two additional sites.

Author: Dr. Andreas Wieser, IMK-TRO

Cosmic-Ray Neutron Sensing (CRNS) is a mobile, non-contact technology for determining mean soil moisture in the vicinity of about 15 hectares. The method is based on the detection of neutrons "reflected" in the soil. Since these are particularly sensitive to hydrogen atoms, a direct dependence of neutron intensity on the prevailing water in the root zone around the sensor can be deduced. Since the neutrons are derived from cosmic events, such as stellar explosions, this measurement method is called Cosmic-Ray Neutron Sensing.

Inside the sensor are usually detector gases (e.g., helium) that react to neutrons passing through and generate a pulse of current. These pulses are counted and stored in the data logger along with information such as GPS coordinates, temperature, air pressure and humidity. The information collected can be used to estimate soil moisture from the signal.

The stationary sensors are already being used successfully in research and agriculture to measure hourly changes in soil moisture over several years. To obtain information about an entire field or a specific catchment area, the detector can be used in mobile mode, called roving. In this mode, the sensor is installed in a vehicle and simply counts neutrons while the vehicle is moving. Measurement data and coordinates are collected every 10 seconds so that an average soil moisture can be calculated for the distance traveled.

As part of the Swabian MOSES 2023 measurement campaign, a stationary cosmic-ray sensor will be installed at the main site in Villingen-Schwenningen. Thus, the mean soil moisture within a radius of about 200m around the sensor and the change over the entire measurement period can be determined.

In the catchment area of the Lindach river, event-related runs are carried out with a mobile Cosmic-Ray-Rover. Before and after heavy rain events, a fixed route is driven so that changes in soil moisture due to precipitation can be determined at the landscape scale. In order to validate the measurement results of the mobile sensor, the locations of the soil moisture networks in the Lindach catchment area are approached. At the respective stations, the vehicle is parked next to the soil moisture network for five to ten minutes, since the measurement uncertainty is lower the longer the rover stays at a location. This allows the results of both measurement methods to be compared at specific points.

A solid estimate of soil moisture at the landscape scale is relevant for hydrological modeling. This can be used to predict future weather developments, for example to estimate the risk from droughts, heat waves or floods (see research objectives).

Authors: Mandy Kasner, Prof. Dr. Peter Dietrich, UFZ

Additional information on Cosmic Ray Neutron Sensing & Roving and its use in other projects: Homepage

The vertical temperature and humidity profile of the atmosphere is crucial for the formation and intensity of thunderstorm events. In addition, the three-dimensional (3D) wind field, especially in the upwind region of a thundercloud, determines the strength of precipitation in the form of rain or hail (see research objectives).

Using the small (size of a yogurt cup) and lightweight (12 gram) swarm probes of Sparv vertical profiles of air temperature, humidity, pressure and the 3D wind field can be measured directly in a thundercloud during mobile deployment. They transmit the measured parameters every 4 seconds via radio to the mobile ground station. A real-time map continuously displays the position of all probes. The swarm probe is a new type of measuring instrument that provides several series of measurements in a defined air volume for up to one hour. Up to 17 balloon-borne probes can be launched simultaneously or in close proximity, for example directly in front of a thundercloud. The probes ascend to a user-defined altitude and then follow the flow in the thundercloud on so-called Lagrangian orbits.

The individual probes can be separated from the balloons in the further course either by remote command or from a further, previously defined height and thus fall to the ground. Due to their low weight, the fall velocity and thus the momentum when hitting the ground is low, so that the probes can be used several times (if they are recovered).

Author: Prof. Dr. Michael Kunz, IMK-TRO

The Wingcopter Eddy Covariance Drone is a measuring system developed to determine the exchange of greenhouse gases between the atmosphere and ground-level sources or sinks (such as vegetation, soil organisms or mofettes).

For this purpose, it is equipped with a five-hole probe wind measuring instrument, a fine-wire thermometer that measures particularly quick and sensitive, and a combined carbon dioxide/water vapour sensor. In future is is planned to add a laser methane sensor.

The Eddy covariance method is the methodological and mathematical basis of the measuring system. In the presence of a vertical gradient of an atmospheric variable (such as a gas concentration), it describes the systematic relationship between the vertical movement of air parcels with which this variable is transported and its resulting change at a given measurement height.

This vertical motion is determined as a component of the three-dimensional wind field with the five-hole probe instrument. This instrument uses the differences of the dynamic pressures, which are applied directionally to the slightly inclined pressure holes of the probe, in order to measure the relative inflow of the drone flying horizontally at about 50 meters above the ground at a speed of about 80 km/h. At the same time, the exact flight attitude of the drone is determined. The atmospheric wind field in which the drone is moving is then determined by simultaneously recording its exact flight attitude and movement using inertial and satellite navigation. Rapid determination of gas concentrations in the air parcels moving with the wind field is achieved by measuring the concentration-dependent absorption of infrared radiation by these gases inside the measurement system.

Over areas that are particularly relevant to the climate system and worthy of consideration for climate research, the Wingcopter Eddy Covariance Drone can thus be used to quantify the vertical fluxes of humidity, heat and, in particular, of the greenhouse gases mentioned, and thus to study and balance them in greater detail (see research objectives).

Author: Prof. Dr. Torsten Sachs, GFZ