An Exploratory Investigation of UAS Regulations in Europe and the Impact on Effective Use and Economic Potential

Unmanned aircraft systems (UAS) have rapidly become more common in various applications. At the same time, the need for a safe UAS operation is of great importance to minimize and avoid risks that could arise with the deployment of this technology. With these requirements, UAS regulators in the European Union (EU) are making large efforts to enable a reliable legal framework of conditions for UAS operation to keep up with new capabilities of this technology and to minimize the risk of property damage and, most importantly, human injury. A recent outcome of the mentioned efforts is that new EU drone regulations are into force since 1 January 2021. In this paper we aim to provide a sound overview of recent EU drone regulations and the main changes to the rules since the first wave of regulations adopted in 2017. We highlight how such new rules help or hinder the use of UAS technology and its economic potential in scientific and commercial sectors by providing an exploratory investigation of UAS legal frames in Europe. An example of the impact of legislation on the operation of one particular UAS in Germany is provided, which has been in use since 2013 for atmospheric research

Ein Beitrag zum verbesserten Verständnis von Prozessen in der atmosphärischen Grenzschicht mit fluggestützten hochauflösenden Messungen

The habilitation thesis investigates atmospheric boundary layer processes. Different applications of airborne high resolution measurements are provided, which result in improved understanding these processes. After the introduction, the different airborne carrier platforms used in the studies are presented, ranging from unmanned systems of few kg to manned aircraft, and the methods and sensors of importance to the scientific case studies are shown. Applications for improved understanding include the development of low-level jets and their contribution to for wind energy the impact of the low-level jet on turbulence anisotropy wakes behind offshoe wind parks suitable sensors for determining airborne latent heat fluxes the formation of new particles directly in the atmosphere The thesis ends with an outlook on future developments in the field of airborne meteorological research.Die vorliegende Arbeit befasst sich mit Prozessen in der atmosphärischen Grenzschicht. Verschiedene Anwendungen von fluggestützten hochaufgelösten Messungen werden dargestellt, die zu einem verbesserten Verständnis der Grenzschichtprozesse führen. Nach der Einleitung werden die verschiedenen für die Studien relevanten fluggestützten Systeme vorgestellt, die von unbemannten Systemen mit wenigen kg bis zu bemannten Flugzeugen reichen. Ebenso werden die Methoden und Sensoren dargestellt, auf denen die wissenschaftlichen Fallstudien basieren. Auf den folgenden Anwendungsgebieten konnte damit ein Beitrag zum besseren Verständnis der Prozesse in der Grenzschicht geleistet werden: Die Entwicklung des Grenzschicht-Strahlstroms (Low-Level Jet) und seine Bedeutung für die Windenergie Die Auswirkung eines Grenzschicht-Strahlstroms auf die Anisotropie von Turbulenz Nachläufe hinter Offshore-Windparks Geeignete Sensoren zur Erfassung von latenten Wärmeflüssen Die Entstehung von neuen Partikeln direkt in der Atmosphäre Die Arbeit schließt mit einem Ausblick auf die zukünftige Entwicklung auf dem Gebiet der fluggestützten meteorologischen Forschung

Airborne LiDAR Measurements of Sea Surface Properties in the German Bight

Sea surface measurements are mainly gathered using satellite altimeter, buoy, and platform measurements. Satellite measurements typically have a coarse spatial resolution and need recalibration in coastal regions, whereas point measurements of buoys only represent limited areas around the measurement point because of the complex coastal bathymetry. Wave models (WAM) are used to expand the sparse observations in space and time. As a part of the project WIndPArk far-field (WIPAFF), which focused on wakes behind offshore wind farms, extensive airborne light detection and ranging (LiDAR) measurements of ocean waves in the German Bight were performed for more than 90 h. The LiDAR data processed for significant wave height can be used to validate and improve WAM models for complex areas and fill the observation gap between satellite altimeter and point measurements. This creates a detailed picture of the sea surface for coastal engineering and environmental applications. After introducing the measurement techniques and the data situation, intercomparisons between the available airborne measurements, buoy data, and WAM model output are presented to provide an insight into the potential of airborne LiDAR measurements for wave characterization and wave model validation

The Role of Atmospheric Stability and Turbulence in Offshore Wind-Farm Wakes in the German Bight

Airborne meteorological in situ measurements as well as stationary measurements at the offshore masts FINO1 and FINO3 in the German Bight are evaluated in order to examine the hypothesis that the wake dissipation downstream of large offshore wind farms depends on atmospheric stability. A long-term study of the mast data for the years 2016 and 2017 demonstrates a clear dependence of stability on the wind direction. Stable conditions are predominantly expected during southerly winds coming from the land. The analysis of various stability and turbulence criteria shows that the lapse rate is the most robust parameter for stability classification in the German Bight, but further implies that stability depends on the measurement height. A near-surface (0 to 30 m), predominantly convective, layer is present and more stable conditions are found aloft (55 to 95 m). Combing the stability data with the airborne measurements of the offshore wind-farm wakes reveals the trend of a correlation between longer wake lengths and an increase in the initial wind-speed deficit downwind of a wind farm with stronger thermal stability. However, the stability correlation criteria with the wake length downstream of the four investigated wind farms, Godewind, Amrumbank West, Meerwind Süd/Ost, and Nordsee Ost, contain large variance. It is assumed that the observed scattering is due to the influence of the wind-farm architecture and temperature inversions around hub height. These, however, are crucial for the classification of stability and illustrate the complexity of a clear stability metric

Coastal horizontal wind speed gradients in the North Sea based on observations and ERA5 reanalysis data

The transition from land to sea affects the wind field in coastal regions. From the perspective of near-coastal offshore wind farms, the coastal transition complicates the task of energy resource assessment by, for example, introducing non-homogeneity into the free wind field. To help elucidate the matter, we quantify the average horizontal wind speed gradients at progressively increasing distances from the German coast using two years of hourly ERA5 reanalysis data, and further describe the dependence of wind speed gradients on the measurement height, atmospheric stability, and season. A vertical wind lidar located on Norderney Island near the German mainland acts as our observational reference for the ERA5 data, where a good agreement ( R 2 = 0 . 9 3 $R^2 =\nobreak 0.93$ ) is found despite the relatively coarse ERA5 data resolution. Interestingly, the comparison of lidar data with the higher-resolution Weather Research and Forecasting (WRF) mesoscale model yields good but relatively weaker agreement ( R 2 = 0 . 8 5 $R^2 =\nobreak 0.85$ ). The ERA5 data reveal that, for flow over the North Sea originating from the German mainland from the south, the wind speed at 10 m (110 m) above sea level increases by 30 % (20 %) some 80 km from the coast on average, and by 5 % at larger heights. An increased stratification increases the horizontal wind speed gradient at 10 m above sea level but decreases it at 110 m. Case studies using satellite and flight measurements are first analyzed to help reveal some of the underlying mechanisms governing horizontal wind speed gradients, including cases of decreasing wind speed with increasing distance from the coast, in which stable flow of warm air over the colder sea leads to an overall deceleration of the flow. The accuracy of offshore resource assessment appears to profit from utilising the horizontal wind speed gradient information contained in ERA5 reanalysis data

Concept and Feasibility Evaluation of Distributed Sensor-Based Measurement Systems Using Formation Flying Multicopters

Unmanned aerial vehicles (UAVs) have been used for increasing research applications in atmospheric measurements. However, most current solutions for these applications are based on a single UAV with limited payload capacity. In order to address the limitations of the single UAV-based approach, this paper proposes a new concept of measurements using tandem flying multicopters as a distributed sensor platform. Key challenges of the proposed concept are identified including the relative position estimation and control in wind-perturbed outdoor environment and the precise alignment of payloads. In the proposed concept, sliding mode control is chosen as the relative position controller and a gimbal stabilization system is introduced to achieve fine payload alignment. The characterization of the position estimation sensors (including global navigation satellite system and real-time kinematics) and flight controller is carried out using different UAVs (a DJI Matrice M600 Pro Hexacopter and Tarot X4 frame based Quadcopter) under different wind levels. Based on the experimental data, the performance of the sliding mode controller and the performance of the gimbal stabilization system are evaluated in a hardware-in-the-loop simulation environment (called ELISSA). Preliminary achievable control accuracies of the relative position and attitude of subsystems in the proposed concept are estimated based on experimental result

Wind Lidar and Radiosonde Measurements of Low-Level Jets in Coastal Areas of the German Bight

For wind energy, the knowledge of the available wind resource is essential. Therefore, specific wind phenomena at the altitude range of wind turbines are currently the focus of investigations. One such specific feature is the low-level jet (LLJ). The article analyses LLJ properties at two locations in the German Bight: A wind lidar system for measuring wind profiles at heights from 50 m to 500 m a.g.l. (above ground level) was first installed at the offshore island of Heligoland, Germany, and then at the coastal island of Norderney, Germany, for one year. The LLJ is defined here as a maximum horizontal wind speed in the vertical profile of horizontal wind speed followed by a minimum wind speed, independent of the mechanism or origin of the phenomenon. The two sites showed a similar annual and diurnal distribution of LLJ events with a maximum occurrence in spring and summer and during the night, and a most frequent jet core height of around 120 m a.g.l. Based on radiosondes launched from Norderney at midnight and noon, it is shown that LLJ events at noon are most frequent when atmospheric conditions are stable. A case study shows the horizontal extent of an LLJ event over at least 100 km by simultaneous wind lidar measurements at four sites in the German Bight and mesoscale simulations with the weather research and forecast (WRF) model

Towards a Fast, Open-Path Laser Hygrometer for Airborne Eddy Covariance Measurements

Water vapor fluxes play a key role in the energy budget of the atmosphere, and better flux measurements are needed to improve our understanding of the formation of clouds and storms. Large-scale measurements of these fluxes are possible by employing the eddy correlation (EC) method from an aircraft. A hygrometer used for such measurements needs to deliver a temporal resolution of at least 10 Hz while reliably operating in the harsh conditions on the exterior of an aircraft. Here, we present a design concept for a calibration-free, first-principles, open-path dTDLAS hygrometer with a planar, circular and rotationally symmetric multipass cell with new, angled coupling optics. From our measurements, the uncertainty of the instrument is estimated to be below 4.5% (coverage factor k = 1). A static intercomparison between a dTDLAS prototype of the new optics setup and a traceable dew point mirror hygrometer was conducted and showed a systematic relative deviation of 2.6% with a maximal relative error of 2.2%. Combined with a precision of around 1 ppm H₂O at tropospheric conditions, the newly designed setup fulfills the static precision and accuracy requirements of the proposed airborne EC hygrometer

Case studies of the wind field around Ny-Ålesund, Svalbard, using unmanned aircraft

The wind field in Arctic fjords is strongly influenced by glaciers, local orography and the interaction between sea and land. Ny-Ålesund, an important location for atmospheric research in the Arctic, is located in Kongsfjorden, a fjord with a complex local wind field that influences measurements in Ny-Ålesund. Using wind measurements from UAS (unmanned aircraft systems), ground measurements, radiosonde and reanalysis data, characteristic processes that determine the wind field around Ny-Ålesund are identified and analysed. UAS measurements and ground measurements show, as did previous studies, a south-east flow along Kongsfjorden, dominating the wind conditions in Ny-Ålesund. The wind measured by the UAS in a valley 1 km west of Ny-Ålesund differs from the wind measured at the ground in Ny-Ålesund. In this valley, we identify a small-scale catabatic flow from the south to south-west as the cause for this difference. Case studies show a backing (counterclockwise rotation with increasing altitude) of the wind direction close to the ground. A katabatic flow is measured near the ground, with a horizontal wind speed up to 5 m s-1. Both the larger-scale south-east flow along the fjord and the local katabatic flows lead to a highly variable wind field, so ground measurements and weather models alone give an incomplete picture. The comparison of UAS measurements, ground measurements and weather conditions analysis using a synoptic model is used to show that the effects measured in the case studies play a role in the Ny-Ålesund wind field in spring

Long-range modifications of the wind field by offshore wind parks – results of the project WIPAFF

This publication synthesizes the results of the WIPAFF (WInd PArk Far Fields) project. WIPAFF focused on the far field of large offshore wind park wakes (more than 5 km downstream of the wind parks) located in the German North Sea. The research project combined in situ aircraft and remote sensing measurements, satellite SAR data analysis and model simulations to enable a holistic coverage of the downstream wakes. The in situ measurements recorded on-board the research aircraft DO-128 and remote sensing by laser scanner and SAR prove that wakes of more than 50 kilometers exist under certain atmospheric conditions. Turbulence occurs at the lateral boundaries of the wakes, due to shear between the reduced wind speed inside the wake and the undisturbed flow. The results also reveal that the atmospheric stability plays a major role in the evolution of wakes and can increase the wake length significantly by a factor of three or more. On the basis of the observations existing mesoscale and industrial models were validated and updated. The airborne measurement data is available at PANGAEA/ESSD