Stephan T. Kral

Stephan T. Kral
University of Bergen | UiB · Geophysical Institute

PhD

About

30
Publications
7,747
Reads
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475
Citations
Introduction
Stephan T. Kral currently works at the Geophysical Institute, University of Bergen. Stephan does research in Meteorology and Aerospace Engineering. He is currently working on the "Innovative Strategies for Observations in the Arctic Atmospheric Boundary Layer (ISOBAR)" project.
Additional affiliations
April 2016 - June 2016
University of Bergen
Position
  • PhD Student

Publications

Publications (30)
Preprint
Full-text available
This study introduces the SAMURAI-S, a novel measurement system that incorporates a state-of-the-art sonic anemometer combined with a multi-rotor drone in a sling load configuration, designed to overcome the limitations of traditional mast-based observations in terms of spatial flexibility. This system enables the direct measurement of 3D wind vect...
Article
Full-text available
Ultrasonic anemometers mounted on rotary-wing drones have the potential to provide a cost-efficient alternative to the classical meteorological mast-mounted counterpart for atmospheric boundary layer research. However, the propeller-induced flow may degrade the accuracy of free-stream wind velocity measurements by wind sensors mounted on drones – a...
Article
Full-text available
Empirical damage model Impingement to end of incubation Offshore conditions Leading edge erosion on wind turbine blades is a common issue, particularly for wind turbines placed in regions characterized by high wind speeds and precipitation. This study presents the development of a rain erosion atlas for Scandinavia and Finland, based on ERA5 reanal...
Article
Full-text available
The availability of multi-rotor UAVs with lifting capacities of several kilograms allows for a new paradigm in atmospheric measurement techniques, i.e., the integration of research-grade sonic anemometers for airborne turbulence measurements. With their ability to hover and move very slowly, this approach yields unrevealed flexibility compared to m...
Preprint
Full-text available
The availability of multi-rotor UAVs with lifting capacities of several kilograms, allows for a new paradigm in atmospheric measurement techniques, i.e. the integration of research-grade sonic anemometers for airborne turbulence measurements. With their ability to hover and move very slowly, this approach yields an unrevealed flexibility compared t...
Preprint
Full-text available
Ultrasonic anemometers mounted on rotary-wing drones have the potential to provide a cost-efficient alternative to the classical meteorological mast-mounted counterpart for wind energy applications. However, the propeller-induced flow may deteriorate the accuracy of free wind velocity measurements by wind sensors mounted on the drone. Therefore, we...
Article
Full-text available
This study presents a computational fluid dynamics (CFD) based approach to determine the optimal positioning for an atmospheric turbulence sensor on a rotary-wing uncrewed aerial vehicle (UAV) with X8 configuration. The vertical (zBF) and horizontal (xBF) distances of the sensor to the UAV center to reduce the effect of the propeller-induced flow a...
Article
Full-text available
We explore the potential of a new method for the estimation of profiles of turbulence statistics in the stable boundary layer (SBL). By applying gradient-based scaling to multicopter unoccupied aircraft system (UAS) profiles of temperature and wind, sampled over sea-ice during the 2018 Innovative Strategies for Observations in the Arctic Atmospheri...
Article
Full-text available
A realistic representation of the stable atmospheric boundary layer in numerical weather prediction (NWP) and climate models is still a challenge. We study the evolution of a stable boundary layer over snow‐covered sea ice in Bothnian Bay during wintertime in 2018. We perform high‐resolution model experiments with the Weather Research and Forecasti...
Article
Full-text available
The Winter Process Cruise (WPC) aboard RV Kronprins Haakon (KH2021702) conducted observations on processes that control the position and variability of the polar front in the Northern Barents Sea and the distribution of Arctic and Atlantic water masses. Moreover, the WPC serviced 2 gateway moorings sites (M1 and M4) and collected complementary hydr...
Thesis
Full-text available
In this thesis, consisting of five scientific papers, I investigate the potential of unmanned aircraft systems (UAS) in stable boundary layer (SBL) research, by developing and applying a new innovative observation strategy. In this strategy, we supplement ground-based micrometeorological observations from masts and remote-sensing systems with a num...
Article
Full-text available
The Innovative Strategies for Observations in the Arctic Atmospheric Boundary Layer Program (ISOBAR) is a research project investigating stable atmospheric boundary layer (SBL) processes, whose representation still poses significant challenges in state-of-the-art numerical weather prediction (NWP) models. In ISOBAR ground-based flux and profile obs...
Article
Because unmanned aircraft systems (UAS) offer new perspectives on the atmosphere, their use in atmospheric science is expanding rapidly. In support of this growth, the International Society for Atmospheric Research Using Remotely-Piloted Aircraft (ISARRA) has been developed and has convened annual meetings and “flight weeks.” The 2018 flight week,...
Article
Full-text available
For atmospheric boundary-layer (ABL) studies, unmanned aircraft systems (UAS) can provide new information in addition to traditional in-situ measurements, or by ground-or satellite-based remote sensing techniques. The ability of fixed-wing UAS to transect the ABL in short time supplement ground-based measurements and the ability to extent the data...
Article
Full-text available
Small unmanned aircraft systems (sUAS) are rapidly transforming atmospheric research. With the advancement of the development and application of these systems, improving knowledge of best practices for accurate measurement is critical for achieving scientific goals. We present results from an intercomparison of atmospheric measurement data from the...
Article
Full-text available
The aim of the research project “Innovative Strategies for Observations in the Arctic Atmospheric Boundary Layer (ISOBAR)” is to substantially increase the understanding of the stable atmospheric boundary layer (SBL) through a combination of well-established and innovative observation methods as well as by models of different complexity. During thr...
Data
SODAR wind profile data, measured during the Norwegian Young Sea-Ice Experiment (Jan - Jun 2015) for the period 06.05--04.06.2015. The data contains profiles of: - horizontal wind speed; - wind direction; - vertical wind speed; - standard deviation of the vertical wind at 48 vertical levels between 30 m and 500 m agl. (10 m spacing), and a time...
Article
We discuss scalar similarities and dissimilarities based on analysis of the dissipation terms in the variance budget equations, considering the turbulent kinetic energy and the variances of temperature, specific humidity and specific CO2 content. For this purpose, 124 high-frequency sampled segments are selected from the Boundary Layer Late Afterno...
Article
Full-text available
The micro-RPAS (remotely piloted aircraft system) SUMO (Small Unmanned Meteorological Observer) equipped with a five-hole-probe (5HP) system for turbulent flow measurements was operated in 49 flight missions during the BLLAST (Boundary-Layer Late Afternoon and Sunset Turbulence) field campaign in 2011. Based on data sets from these flights, we inve...
Article
Full-text available
The Small Unmanned Meteorological Observer (SUMO) has been operated in the vicinity of five research turbines of the Energy Research Centre of the Netherlands (ECN) at the test site Wieringermeer. The intention of the campaign was to proof the capability of the system for wind turbine wake investigations also for situations above rated wind speed....
Article
Full-text available
In June and July 2011 the RPAS (Remotely Piloted Aircraft System) SUMO (Small Unmanned Meteorological Observer) performed a total number of 299 scientific flights during the BLLAST (Boundary Layer Late Afternoon and Sunset Turbulence) campaign in southern France. Three different types of missions were performed: vertical profiling of the mean meteo...
Article
Full-text available
The budget equation components for turbulent kinetic energy (TKE) and the variances of virtual potential temperature, specific humidity, and specific CO2 content have been estimated using the Inertial Dissipation and Eddy Covariance methods. A discussion with four examples is provided about the normalization used for comparing different tracer spec...
Article
Full-text available
The micro-RPAS SUMO (Small Unmanned Meteorological Observer) equipped with a five hole probe (5HP) system for turbulent flow measurements has been operated in 49 flight missions during the BLLAST (Boundary-Layer Late Afternoon and Sunset Turbulence) field campaign in 2011. Based on data sets from these flights we investigate the potential and limit...
Article
Full-text available
In June and July 2011 the RPA system SUMO performed a total number of 299 scientific flights during the BLLAST campaign in Southern France. Three different types of missions have been performed, vertical profiling of the mean meteorological parameters temperature, humidity and wind, horizontal surveys of the surface temperature and horizontal transec...
Article
Full-text available
This guidebook addresses recent knowledge and good practices on the risk of adverse weather events for passenger as well as air cargo services. It offers best practice guidance on how passengers may react and how companies should be prepared. It describes what kind of information can be used as support and how information networks and information s...
Article
The summer atmospheric boundary layer over a fjord in the High Arctic has been investigated during three consecutive years (2008–2010). Measurements of turbulent surface layer fluxes of momentum and sensible heat using a sonic anemometer and slow-response instruments were taken from a tower on the coast of Isfjorden, Svalbard, and analysed for seas...
Article
Full-text available
The present paper presents a data-driven method for assessing the resilience of the Euro-pean passenger transport network during extreme weather events. The method aims to fill in the gap of current research efforts regarding the quantification of impacts attributed to climate change and the identification of substitutability opportunities between...

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