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

The vertical variability of black carbon observed in the atmospheric boundary layer during DACCIWA

This study underlines the important role of the transported black carbon (BC) mass concentration in the West African monsoon (WAM) area. BC was measured with a micro-aethalometer integrated in the payload bay of the unmanned research aircraft ALADINA (Application of Light-weight Aircraft for Detecting IN situ Aerosol). As part of the DACCIWA (Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa) project, 53 measurement flights were carried out at Savè, Benin, on 2–16 July 2016. A high variability of BC (1.79 to 2.42±0.31 µg m−3) was calculated along 155 vertical profiles that were performed below cloud base in the atmospheric boundary layer (ABL). In contrast to initial expectations of primary emissions, the vertical distribution of BC was mainly influenced by the stratification of the ABL during the WAM season. The article focuses on an event (14 and 15 July 2016) which showed distinct layers of BC in the lowermost 900 m above ground level (a.g.l.). Low concentrations of NOx and CO were sampled at the Savè supersite near the aircraft measurements and suggested a marginal impact of local sources during the case study. The lack of primary BC emissions was verified by a comparison of the measured BC with the model COSMO-ART (Consortium for Small-scale Modelling–Aerosols and Reactive Trace gases) that was applied for the field campaign period. The modelled vertical profiles of BC led to the assumption that the measured BC was already altered, as the size was mainly dominated by the accumulation mode. Further, calculated vertical transects of wind speed and BC presume that the observed BC layer was transported from the south with maritime inflow but was mixed vertically after the onset of a nocturnal low-level jet at the measurement site. This report contributes to the scope of DACCIWA by linking airborne BC data with ground observations and a model, and it illustrates the importance of a more profound understanding of the interaction between BC and the ABL in the WAM region

New Setup of the UAS ALADINA for Measuring Boundary Layer Properties, Atmospheric Particles and Solar Radiation

The unmanned research aircraft ALADINA (Application of Light-weight Aircraft for Detecting in situ Aerosols) has been established as an important tool for boundary layer research. For simplified integration of additional sensor payload, a flexible and reliable data acquisition system was developed at the Institute of Flight Guidance, Technische Universität (TU) Braunschweig. The instrumentation consists of sensors for temperature, humidity, three-dimensional wind vector, position, black carbon, irradiance and atmospheric particles in the diameter range of ultra-fine particles up to the accumulation mode. The modular concept allows for straightforward integration and exchange of sensors. So far, more than 200 measurement flights have been performed with the robustly-engineered system ALADINA at different locations. The obtained datasets are unique in the field of atmospheric boundary layer research. In this study, a new data processing method for deriving parameters with fast resolution and to provide reliable accuracies is presented. Based on tests in the field and in the laboratory, the limitations and verifiability of integrated sensors are discussed

Secondary aerosol formation in marine Arctic environments : a model measurement comparison at Ny-Ålesund

In this study, we modeled the aerosol particle formation along air mass trajectories arriving at the remote Arctic research stations Gruvebadet (67 m a.s.l) and Zeppelin (474 m a.s.l), Ny-Ålesund during May 2018. The aim of this study was to improve our understanding of processes governing secondary aerosol formation in remote Arctic marine environments. We run the Lagrangian chemistry transport model ADCHEM, along air mass trajectories generated with FLEXPART v10.4. The air masses arriving at Ny-Ålesund spend most of their time over the open ice-free ocean. In order to capture the secondary aerosol formation from the DMS emitted by phytoplankton on the ocean surface, we implemented a recently developed comprehensive DMS and halogen multi-phase oxidation chemistry scheme, coupled with the widely used Master Chemical Mechanism (MCM). The modeled median particle number size distributions are in close agreement with the observations in the marine influenced boundary layer at near sea surface Gruvebadet site. However, while the model reproduces the accumulation mode particle number concentrations at Zeppelin, it overestimates the Aitken mode particle number concentrations by a factor of ~5.5. We attribute this to the deficiency of the model to capture the complex orographic effects on the boundary layer dynamics at Ny-Ålesund. The model also reproduces the average vertical particle number concentration profiles within the boundary layer (0-600 m a.s.l.) above Gruvebadet, as measured with Condensation Particle Counters (CPCs) on board an Unmanned Aircraft Systems (UAS). The model successfully reproduces the observed Hoppel minima, often seen in particle number size distributions at Ny-Ålesund. The model also supports the previous experimental findings that ion mediated H2SO4-NH3 nucleation can explain the observed new particle formation in the marine Arctic boundary layer in the vicinity of Ny-Ålesund. Precursors resulting from gas and aqueous phase DMS chemistry contribute to the subsequent growth of the secondary aerosols. The growth of particles is primarily driven via H2SO4 condensation and formation of methane sulfonic acid (MSA) through the aqueous-phase ozonolysis of methane sulfinic acid (MSIA) in cloud and deliquescent droplets.Peer reviewe

Unmanned Aerial Systems for Investigating the Polar Atmospheric Boundary Layer—Technical Challenges and Examples of Applications

Unmanned aerial systems (UAS) fill a gap in high-resolution observations of meteorological parameters on small scales in the atmospheric boundary layer (ABL). Especially in the remote polar areas, there is a strong need for such detailed observations with different research foci. In this study, three systems are presented which have been adapted to the particular needs for operating in harsh polar environments: The fixed-wing aircraft M^2AV with a mass of 6 kg, the quadrocopter ALICE with a mass of 19 kg, and the fixed-wing aircraft ALADINA with a mass of almost 25 kg. For all three systems, their particular modifications for polar operations are documented, in particular the insulation and heating requirements for low temperatures. Each system has completed meteorological observations under challenging conditions, including take-off and landing on the ice surface, low temperatures (down to −28 °C), icing, and, for the quadrocopter, under the impact of the rotor downwash. The influence on the measured parameters is addressed here in the form of numerical simulations and spectral data analysis. Furthermore, results from several case studies are discussed: With the M^2AV, low-level flights above leads in Antarctic sea ice were performed to study the impact of areas of open water within ice surfaces on the ABL, and a comparison with simulations was performed. ALICE was used to study the small-scale structure and short-term variability of the ABL during a cruise of RV Polarstern to the 79°N glacier in Greenland. With ALADINA, aerosol measurements of different size classes were performed in Ny-Ålesund, Svalbard, in highly complex terrain. In particular, very small, freshly formed particles are difficult to monitor and require the active control of temperature inside the instruments. The main aim of the article is to demonstrate the potential of UAS for ABL studies in polar environments, and to provide practical advice for future research activities with similar systems

Unmanned Aerial Systems for Investigating the Polar Atmospheric Boundary Layer—Technical Challenges and Examples of Applications

Unmanned aerial systems (UAS) fill a gap in high-resolution observations of meteorological parameters on small scales in the atmospheric boundary layer (ABL). Especially in the remote polar areas, there is a strong need for such detailed observations with different research foci. In this study, three systems are presented which have been adapted to the particular needs for operating in harsh polar environments: The fixed-wing aircraft M2AV with a mass of 6 kg, the quadrocopter ALICE with a mass of 19 kg, and the fixed-wing aircraft ALADINA with a mass of almost 25 kg. For all three systems, their particular modifications for polar operations are documented, in particular the insulation and heating requirements for low temperatures. Each system has completed meteorological observations under challenging conditions, including take-offand landing on the ice surface, low temperatures (down to-28 °C), icing, and, for the quadrocopter, under the impact of the rotor downwash. The influence on the measured parameters is addressed here in the form of numerical simulations and spectral data analysis. Furthermore, results from several case studies are discussed: With the M2AV, low-level flights above leads in Antarctic sea ice were performed to study the impact of areas of open water within ice surfaces on the ABL, and a comparison with simulations was performed. ALICE was used to study the small-scale structure and short-term variability of the ABL during a cruise of RV Polarstern to the 79° N glacier in Greenland. With ALADINA, aerosol measurements of different size classes were performed in Ny-Alesund, Svalbard, in highly complex terrain. In particular, very small, freshly formed particles are difficult to monitor and require the active control of temperature inside the instruments. The main aim of the article is to demonstrate the potential of UAS for ABL studies in polar environments, and to provide practical advice for future research activities with similar systems. © 2020 by the authors

Overview: Integrative and Comprehensive Understanding on Polar Environments (iCUPE) – concept and initial results

The role of polar regions is increasing in terms of megatrends such as globalization, new transport routes, demography, and the use of natural resources with consequent effects on regional and transported pollutant concentrations. We set up the ERA-PLANET Strand 4 project “iCUPE – integrative and Comprehensive Understanding on Polar Environments” to provide novel insights and observational data on global grand challenges with an Arctic focus. We utilize an integrated approach combining in situ observations, satellite remote sensing Earth observations (EOs), and multi-scale modeling to synthesize data from comprehensive long-term measurements, intensive campaigns, and satellites to deliver data products, metrics, and indicators to stakeholders concerning the environmental status, availability, and extraction of natural resources in the polar areas. The iCUPE work consists of thematic state-of-the-art research and the provision of novel data in atmospheric pollution, local sources and transboundary transport, the characterization of arctic surfaces and their changes, an assessment of the concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, the quantification of emissions from natural resource extraction, and the validation and optimization of satellite Earth observation (EO) data streams. In this paper we introduce the iCUPE project and summarize initial results arising out of the integration of comprehensive in situ observations, satellite remote sensing, and multi-scale modeling in the Arctic context

Atmospheric boundary layer dynamics and aerosol properties based on observations of unmanned research aircraft

The outline of the thesis considers a characterization of dynamic processes and aerosol particles that were studied with unmanned aerial systems (UAS) in the atmospheric boundary layer (ABL) at two investigation areas; in the polar region and at a continental site in Middle Europe. The use of UAS provides a detailed 4-D picture of ABL properties, thus offers a high potential for filling the sparse small-scale observations that exist in the ABLdue to missing measurement tools. The Carolo T200 ”M2AV” (Mini Meteorological Aerial Vehicle) was applied for ABL profiling and investigations of turbulence parameters as part of a Polarstern cruise in the Antarctic Weddell-Sea during polar night between 8 June and 12 August 2013. Eleven research flights were carried out with the M2AV but the field activity was strongly affected by a multitude of critical challenges like icing, strong wind speed and externally driven limitations, mainly influenced by the need of a suitable airfield on sea ice. The results address a detailed investigation of the ABL’s stability, measured above closed sea ice and above open water sections at two different sites on 11 July and 1–2 August 2013. The observations are strongly questioning the common picture of a stably stratified ABL, as generally assumed in models that are applied for polar areas. Since October 2013, the UAS Carolo P360 ”ALADINA” (Application of Light-weight Aircraft for Detecting IN-situ Aerosol) was operated for more than 100 research flights at the Leibniz Institute for Tropospheric Research (TROPOS) site in Melpitz, Germany. The main focus of the study is on investigating the correlation between ABL’s properties and the new particle formation (NPF). This was primarily realized by targeting vertical profiles of ultrafine aerosol particles (UFP, usual size <50 nm) in the lowermost 1 km. According to different selected case studies, a high variability of the observed UFP was identified in the vertical scale and the major impact on the distribution was linked to dynamics of the ABL. In addition, frequently performed profiles of the measured UFP enabled to determine transport and mixing processes. For instance, UFP were lifted upwards from the ground or transported downwards mainly originated from the inversion layer or mixed in short time in the whole ABL. Further, to a significant degree of the ALADINA’s measurement period, NPF events would not have been captured by pure ground-based observationsIn dieser Dissertation werden mit Hilfe von unbemannten Forschungsflugzeugen dynamische Prozesse und Aerosolpartikel innerhalb der atmosphärischen Grenzschicht (AGS) an zwei unterschiedlichen Messstandorten (Polargebiet und kontinentaler Raum in Mitteleuropa) untersucht. Der Einsatz von unbemannten Flugsystemen liefert einen erheblichen Beitrag zu aktuell bestehenden Datenlücken, die auf Grund fehlender Messmethoden im kleinskaligen Raum innerhalb der AGS existieren. Das unbemannte Forschungsflugzeug vom Typ Carolo T200 ”M2AV” (Mini Meteorological Aerial Vehicle) wurde auf einer Polarstern- Forschungsfahrt im antarktischen Weddellmeer, unter dem Einfluss der Polarnacht, eingesetzt. Im zwölfwöchigen Zeitraum vom 8. Juni bis 12. August 2013 wurden elf Messflüge durchgeführt, wobei der Feldeinsatz durch die Gegebenheiten vor Ort stark eingeschränkt wurde, wie zum Beispiel häufiges Auftreten von starken Winden, Vereisung und äußeren Einschränkungen, welche unter anderem der Bedingung einer geeigneten Startbahn auf dem Meereis unterlagen. Die Untersuchung von Vertikalprofilen und horizontal durchgeführten Flügen bezieht sich im Speziellen auf den Messzeitraum vom 11. Juli 2013 über geschlossenem Meereis und zwischen dem 1. und 2. August 2013 über unterbrochener Meereisoberfläche. Die gewonnenen Daten sind in ihrer Form einzigartig und stellen das typische Bild einer stabil geschichteten AGS in Frage, wie es allerdings für globale Modelle im Bereich der Polargebiete implementiert wird. Seit Oktober 2013 wird das unbemannte Flugsystem Carolo P360 ”ALADINA” (Application of Light-weight Aircraft for Detecting IN-situ Aerosol) eingesetzt mit dem vorrangingen Ziel die Partikelneubildung zu untersuchen. Der Kern dieser Arbeit befasst sich mit der Wechselwirkung zwischen der kontinental ausgeprägten AGS und der Verteilung von ultrafeinen Partikeln (UFP, Größenbereich definitionsgemäß <50 nm) auf Basis von über 100 Messflügen, welche an der Forschungsstation des TROPOS (Leibniz Institut für Troposphärenforschung) in Melpitz durchgeführt wurden. Anhand diverser Fallstudien wird eine vielfältige Verteilung von UFP innerhalb von 1km Höhe aufgezeigt, welche größtenteils von dynamischen Prozessen in derAGSabhängt. Zudem ermöglicht eine häufige Sondierung mit ALADINA die Betrachtung von Transport- und Mischungsprozessen der gemessenen UFP. So wurden beispielsweise UFP vom Boden aus in die AGS transportiert oder aus der Inversionsschicht in Richtung Boden heruntergemischt. Des Weiteren hätte ein Großteil der durchgeführten ALADINA-Messtage, allein unter Einbezug von Bodenmessdaten, nicht als sogenanntes Partikelneubildungsevent klassifiziert werden können