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  • 1
    Dissertations
    Dissertations
    Wechselwirkung der atmosphärischen Grenzschicht mit synoptisch-skaligen Prozessen während der N-ICE2015 Kampagne (2018)
    Potsdam
    Details Availability
    Call number: AWI A7-20-93463
    Description / Table of Contents: Die Arktis erwärmt sich schneller als der Rest der Erde. Die Auswirkungen manifestieren sich unter Anderem in einer verstärkten Erwärmung der arktischen Grenzschicht. Diese Arbeit befasst sich mit Wechselwirkungen zwischen synoptischen Zyklonen und der arktischen Atmosphäre auf lokalen bis überregionalen Skalen. Ausgangspunkt dafür sind Messdaten und Modellsimulationen für den Zeitraum der N-ICE2015 Expedition, die von Anfang Januar bis Ende Juni 2015 im arktischen Nordatlantiksektor stattgefunden hat. Anhand von Radiosondenmessungen lassen sich Auswirkungen von synoptischen Zyklonen am deutlichsten im Winter erkennen, da sie durch die Advektion warmer und feuchter Luftmassen in die Arktis den Zustand der Atmosphäre von einem strahlungs-klaren in einen strahlungs-opaken ändern. Obwohl dieser scharfe Kontrast nur im Winter existiert, zeigt die Analyse, dass der integrierte Wasserdampf als Indikator für die Advektion von Luftmassen aus niedrigen Breiten in die Arktis auch im Frühjahr geeignet ist. Neben der Advektion von…
    Type of Medium: Dissertations
    Pages: xiv, 147 Seiten , Illustrationen, Diagramme
    URL: https://nbn-resolving.org/urn:nbn:de:kobv:517-opus4-411124
    Language: German
    Note: Inhaltsverzeichnis 1 Einleitung 1.1Wissenschaftliche Zielsetzung 2 Grundlagen 2.1 Grundgleichungen 2.2 Potentielle Vorticity 2.3 Planetare Wellen 2.4 Atmosphärische Instabilität 2.5 Grenzschicht 2.6 Kopplung von Tropo- und Stratosphäre 3 Daten und Methoden 3.1 N-ICE2015 3.1.1 Expeditionsbeschreibung 3.1.2 Ziele der Expedition 3.2 Daten 3.2.1 Beobachtungsdaten 3.2.2 ERA-Interim Reanalyse 3.2.3 Das HIRHAM5 Modell 3.3 Analysemethoden 3.3.1 Temperaturinversionen 3.3.2 Vertikale Stabilität 3.3.3 Grenzschichthöhe 3.3.4 Eady Growth Rate 3.3.5 2d-Skalenfilterung und -Pattern-Korrelation 3.3.6 Nudging Experiment 4 Analyse der N-ICE2015 Radiosonden 4.1 Blick auf die Troposphäre 4.2 Fallstudie zum M2-Sturm: A 4.3 Zyklonencharakteristika 4.4 Temperaturinversionen und Stabilität 4.5 Vergleich mit ERA-Interim, SHEBA und Ny-Ålesund 4.6 Résumé der Expeditionsdaten 5 Nudging Studien mit HIRHAM5 5.1 Vergleich mit ERA-Interim 5.2 Vergleich der Simulationen 5.3 Fallstudie zum M2-Sturm: B 5.3.1 Synoptische Aktivität 5.4 Statistischer Vergleich 6 Einfluss der Stratosphäre 6.1 Stratosphäre im Winter 2014/2015 6.2 Fallstudie zum M2-Sturm: C 6.3 PV als Ladung 6.4 Résumé der Beobachtungen 7 Zusammenfassung und Ausblick A Zusätztliche Abbildungen B Literaturverzeichnis
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  • 2
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    The Arctic Cloud Puzzle: Using ACLOUD/PASCAL Multiplatform Observations to Unravel the Role of Clouds and Aerosol Particles in Arctic Amplification (2019)
    AMER METEOROLOGICAL SOC
    In:  EPIC3Bulletin of the American Meteorological Society, AMER METEOROLOGICAL SOC, 100(5), pp. 841-871, ISSN: 0003-0007
    Details
    Publication Date: 2019-06-17
    Description: Clouds play an important role in Arctic amplification. This term represents the recently observed enhanced warming of the Arctic relative to the global increase of near-surface air temperature. However, there are still important knowledge gaps regarding the interplay between Arctic clouds and aerosol particles, and surface properties, as well as turbulent and radiative fluxes that inhibit accurate model simulations of clouds in the Arctic climate system. In an attempt to resolve this so-called Arctic cloud puzzle, two comprehensive and closely coordinated field studies were conducted: the Arctic Cloud Observations Using Airborne Measurements during Polar Day (ACLOUD) aircraft campaign and the Physical Feedbacks of Arctic Boundary Layer, Sea Ice, Cloud and Aerosol (PASCAL) ice breaker expedition. Both observational studies were performed in the framework of the German Arctic Amplification: Climate Relevant Atmospheric and Surface Processes, and Feedback Mechanisms (AC)3 project. They took place in the vicinity of Svalbard, Norway, in May and June 2017. ACLOUD and PASCAL explored four pieces of the Arctic cloud puzzle: cloud properties, aerosol impact on clouds, atmospheric radiation, and turbulent dynamical processes. The two instrumented Polar 5 and Polar 6 aircraft; the icebreaker Research Vessel (R/V) Polarstern; an ice floe camp including an instrumented tethered balloon; and the permanent ground-based measurement station at Ny-Ålesund, Svalbard, were employed to observe Arctic low- and mid-level mixed-phase clouds and to investigate related atmospheric and surface processes. The Polar 5 aircraft served as a remote sensing observatory examining the clouds from above by downward-looking sensors; the Polar 6 aircraft operated as a flying in situ measurement laboratory sampling inside and below the clouds. Most of the collocated Polar 5/6 flights were conducted either above the R/V Polarstern or over the Ny-Ålesund station, both of which monitored the clouds from below using similar but upward-looking remote sensing techniques as the Polar 5 aircraft. Several of the flights were carried out underneath collocated satellite tracks. The paper motivates the scientific objectives of the ACLOUD/PASCAL observations and describes the measured quantities, retrieved parameters, and the applied complementary instrumentation. Furthermore, it discusses selected measurement results and poses critical research questions to be answered in future papers analyzing the data from the two field campaigns.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 3
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    Microphysical and thermodynamic phase analyses of Arctic low-level clouds measured above the sea ice and the open ocean in spring and summer (2023)
    Copernicus GmbH
    In:  EPIC3Atmospheric Chemistry and Physics, Copernicus GmbH, 23(13), pp. 7257-7280, ISSN: 1680-7316
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    Publication Date: 2023-07-19
    Description: 〈jats:p〉Abstract. Airborne in situ cloud measurements were carried out over the northern Fram Strait between Greenland and Svalbard in spring 2019 and summer 2020. In total, 811 min of low-level cloud observations were performed during 20 research flights above the sea ice and the open Arctic ocean with the Polar 5 research aircraft of the Alfred Wegener Institute. Here, we combine the comprehensive in situ cloud data to investigate the distributions of particle number concentration N, effective diameter Deff, and cloud water content CWC (liquid and ice) of Arctic clouds below 500 m altitude, measured at latitudes between 76 and 83∘ N. We developed a method to quantitatively derive the occurrence probability of their thermodynamic phase from the combination of microphysical cloud probe and Polar Nephelometer data. Finally, we assess changes in cloud microphysics and cloud phase related to ambient meteorological conditions in spring and summer and address effects of the sea ice and open-ocean surface conditions. We find median N from 0.2 to 51.7 cm−3 and about 2 orders of magnitude higher N for mainly liquid clouds in summer compared to ice and mixed-phase clouds measured in spring. A southerly flow from the sea ice in cold air outbreaks dominates cloud formation processes at temperatures mostly below −10 ∘C in spring, while northerly warm air intrusions favor the formation of liquid clouds at warmer temperatures in summer. Our results show slightly higher N in clouds over the sea ice compared to the open ocean, indicating enhanced cloud formation processes over the sea ice. The median CWC is higher in summer (0.16 g m−3) than in spring (0.06 g m−3), as this is dominated by the available atmospheric water content and the temperatures at cloud formation level. We find large differences in the particle sizes in spring and summer and an impact of the surface conditions, which modifies the heat and moisture fluxes in the boundary layer. By combining microphysical cloud data with thermodynamic phase information from the Polar Nephelometer, we find mixed-phase clouds to be the dominant thermodynamic cloud phase in spring, with a frequency of occurrence of 61 % over the sea ice and 66 % over the ocean. Pure ice clouds exist almost exclusively over the open ocean in spring, and in summer the cloud particles are most likely in the liquid water state. The comprehensive low-level cloud data set will help us to better understand the role of clouds and their thermodynamic phase in the Arctic radiation budget and to assess the performance of global climate models in a region of the world with the strongest anthropogenic climate change. 〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
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  • 4
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    The COMBLE campaign: a study of marine boundary-layer clouds in Arctic cold-air outbreaks (2022)
    AMER METEOROLOGICAL SOC
    In:  EPIC3Bulletin of the American Meteorological Society, AMER METEOROLOGICAL SOC, E1371, ISSN: 0003-0007
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    Publication Date: 2022-06-19
    Description: One of the most intense air mass transformations on Earth happens when cold air flows from frozen surfaces to much warmer open water in cold-air outbreaks (CAOs), a process captured beautifully in satellite imagery. Despite the ubiquity of the CAO cloud regime over high-latitude oceans, we have a rather poor understanding of its properties, its role in energy and water cycles, and its treatment in weather and climate models. The Cold-air Outbreaks in the Marine Boundary Layer Experiment (COMBLE) was conducted to better understand this regime and its representation in models. COMBLE aimed to examine the relations between surface fluxes, boundary-layer structure, aerosol, cloud and precipitation properties, and mesoscale circulations in marine CAOs. Processes affecting these properties largely fall in a range of scales where boundary-layer processes, convection, and precipitation are tightly coupled, which makes accurate representation of the CAO cloud regime in numerical weather prediction and global climate models most challenging. COMBLE deployed an Atmospheric Radiation Measurement Mobile Facility at a coastal site in northern Scandinavia (69°N), with additional instruments on Bear Island (75°N), from December 2019 to May 2020. CAO conditions were experienced 19% (21%) of the time at the main site (on Bear Island). A comprehensive suite of continuous in situ and remote sensing observations of atmospheric conditions, clouds, precipitation, and aerosol were collected. Because of the clouds’ well-defined origin, their shallow depth, and the broad range of observed temperature and aerosol concentrations, the COMBLE dataset provides a powerful modeling test bed for improving the representation of mixed-phase cloud processes in large-eddy simulations and large-scale models.
    Repository Name: EPIC Alfred Wegener Institut
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  • 5
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    Overview of the MOSAiC expedition: Atmosphere (2022)
    HUMANA PRESS INC
    In:  EPIC3Elementa Science of the Anthropocene, HUMANA PRESS INC, pp. 1-54, ISSN: 0163-4984
    Details
    Publication Date: 2024-04-23
    Description: With the Arctic rapidly changing, the needs to observe, understand, and model the changes are essential. To support these needs, an annual cycle of observations of atmospheric properties, processes, and interactions were made while drifting with the sea ice across the central Arctic during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition from October 2019 to September 2020. An international team designed and implemented the comprehensive program to document and characterize all aspects of the Arctic atmospheric system in unprecedented detail, using a variety of approaches, and across multiple scales. These measurements were coordinated with other observational teams to explore cross- cutting and coupled interactions with the Arctic Ocean, sea ice, and ecosystem through a variety of physical and biogeochemical processes. This overview outlines the breadth and complexity of the atmospheric research program, which was organized into 4 subgroups: atmospheric state, clouds and precipitation, gases and aerosols, and energy budgets. Atmospheric variability over the annual cycle revealed important influences from a persistent large-scale winter circulation pattern, leading to some storms with pressure and winds that were outside the interquartile range of past conditions suggested by long-term reanalysis. Similarly, the MOSAiC location was warmer and wetter in summer than the reanalysis climatology, in part due to its close proximity to the sea ice edge.The comprehensiveness of the observational program for characterizing and analyzing atmospheric phenomena is demonstrated via a winter case study examining air mass transitions and a summer case study examining vertical atmospheric evolution. Overall, the MOSAiC atmospheric program successfully met its objectives and was the most comprehensive atmospheric measurement program to date conducted over the Arctic sea ice. The obtained data will support a broad range of coupled-system scientific research and provide an important foundation for advancing multiscale modeling capabilities in the Arctic.
    Repository Name: EPIC Alfred Wegener Institut
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