1,721,016 research outputs found
Five-day backwards trajectories at one minute resolution along the flight tracks of the Polar 6 research aircraft during BACSAM I
No full textThe BACSAM I Arctic airborne campaign took place in autumn 2022. It involved the Polar 6 research aircraft stationed in Longyearbyen on Svalbard. Polar 6 was equipped with a wide range of in-situ instruments to measure meteorological and aerosol properties in the Arctic atmosphere around Svalbard and the Fram Strait. In order to understand the origin of air masses sampled by Polar 6, this dataset here was created as follows. For all research flights, every one minute along the flight track and at the coordinates and pressure altitude of Polar 6, one air mass was initialized using the the trajectory calculation tool Lagranto in conjunction with wind fields from the ERA5 reanalysis. Latter has an output resolution of around 30 km and one hour. The hourly data was bi-linearly interpolated to one minute resolution. Trajectories were then calculated five days backwards in one minute steps. Several parameters were traced along the trajectories, based on ERA5 output: Surface pressure, geopotential altitude, atmospheric boundary-layer height, air temperature, specific humidity, sea-ice concentration, and cloud liquid/ice/rain/snow water contents. Thus, it is possible to investigate the origin of the sampled air masses, as well as to estimate the relevant air-mass transformations and cloud processes they underwent during transport towards Polar 6
Five-day backwards trajectories at one minute resolution along the flight tracks of the Polar 6 research aircraft during BACSAM II
No full textThe BACSAM II Arctic airborne campaign took place in spring 2024. It involved the Polar 6 research aircraft stationed in Longyearbyen on Svalbard. Polar 6 was equipped with a wide range of in-situ instruments to measure meteorological and aerosol properties in the Arctic atmosphere around Svalbard and the Fram Strait. In order to understand the origin of air masses sampled by Polar 6, this dataset here was created as follows. For all research flights, every one minute along the flight track and at the coordinates and pressure altitude of Polar 6, one air mass was initialized using the the trajectory calculation tool Lagranto in conjunction with wind fields from the ERA5 reanalysis. Latter has an output resolution of around 30 km and one hour. The hourly data was bi-linearly interpolated to one minute resolution. Trajectories were then calculated five days backwards in one minute steps. Several parameters were traced along the trajectories, based on ERA5 output: Surface pressure, geopotential altitude, atmospheric boundary-layer height, air temperature, specific humidity, sea-ice concentration, and cloud liquid/ice/rain/snow water contents. Thus, it is possible to investigate the origin of the sampled air masses, as well as to estimate the relevant air-mass transformations and cloud processes they underwent during transport towards Polar 6
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Five-day backwards trajectories at one minute resolution along the flight tracks of the Polar 6 research aircraft during HALO-(AC)3
No full textThe HALO-(AC)3 Arctic airborne campaign took place in spring 2022. Among other aircraft, it involved the Polar 6 research aircraft stationed in Longyearbyen on Svalbard. Polar 6 was equipped with a wide range of in-situ instruments to measure meteorological and aerosol properties in the Arctic atmosphere around Svalbard and the Fram Strait. In order to understand the origin of air masses sampled by Polar 6, this dataset here was created as follows. For all research flights, every one minute along the flight track and at the coordinates and pressure altitude of Polar 6, one air mass was initialized using the the trajectory calculation tool Lagranto in conjunction with wind fields from the ERA5 reanalysis. Latter has an output resolution of around 30 km and one hour. The hourly data was bi-linearly interpolated to one minute resolution. Trajectories were then calculated five days backwards in one minute steps. Several parameters were traced along the trajectories, based on ERA5 output: Surface pressure, geopotential altitude, atmospheric boundary-layer height, air temperature, specific humidity, sea-ice concentration, and cloud liquid/ice/rain/snow water contents. Thus, it is possible to investigate the origin of the sampled air masses, as well as to estimate the relevant air-mass transformations and cloud processes they underwent during transport towards Polar 6
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Lagrangian Studies of Arctic Air Mass Transformations During Warm Air Intrusions and Cold Air Outbreaks
No full textIn den letzten 30-40 Jahren hat sich das arktische Klimasystem dramatisch verändert. Phänomene wie der schnelle Rückgang des arktischen Meereises und die beschleunigte Zunahme der oberflächennahen Lufttemperaturen sind wesentliche Kennzeichen der arktischen Verstärkung des Klimawandels, verursacht durch verschiedene Rückkopplungsmechanismen. Der polwärts gerichtete Transport latenter Wärme, hauptsächlich durch Warmlufteinschübe (WLE), hat deutlich zugenommen. In entgegengesetzter Richtung bezeichnen marine Kaltluftausbrüche (KLA) den südwärts gerichteten Transport kalter und trockener arktischer Luftmassen. Sowohl WLE als auch KLA haben große Auswirkungen auf das arktische Klimasystem, doch ihre begleitenden Luftmassentransformationen sind noch nicht vollständig verstanden und quantifiziert. Um diese Lücke zu schließen, kombiniert diese kumulative Dissertation neuartige Lagrange’sche (Luftmassen-folgende) Trajektoranalysen mit atmosphärischen Reanalysen und Beobachtungen von drei kürzlich durchgeführten arktischen Expeditionen.
In Paper I (Kirbus et al., 2023a) wird ein WLE Mitte April 2020 analysiert. Messungen der Expedition Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) zeigen einen raschen Anstieg der 2-m Lufttemperatur um etwa 30K in zwei Tagen und einen anomalen Erwärmungseffekt auf das Energiebudget der Oberfläche. In einem neuen methodischen Ansatz wird die Entwicklung nahezu aller Luftmassen, welche über MOSAiC enden, sowie die relevanten Prozesse und Luftmassentransformationen ausgewertet.
Für Paper II (Kirbus et al., 2023b) wird ein komplexer KLA im Herbst 2020 erforscht. Die gleiche Luftmasse wurde zuerst in der Zentralarktis durch MOSAiC und zwei Tage später in der eisfreien Framstraße durch die Kampagne MOSAiC Airborne observations in the Central Arctic (MOSAiC-ACA) beobachtet. Eine atmosphärische Reanalyse wird genutzt, um die zeitliche Entwicklung der Luftmasse nachzuvollziehen. Darüber hinaus werden Temperatur- und Feuchtetendenzen genutzt, um die Luftmassentransformationen während des Drifts zu untersuchen. Entgegen der Erwartung werden diese Transformationen nicht nur durch Oberflächenveränderungen (Meereis zu offenem Ozean) beeinflusst, sondern auch durch differentielle Advektion von Wolken und Wasserdampf. Die Bedeutung von Windscherung und vertikaler Interaktionen wird hervorgehoben.
Paper III (Kirbus et al., 2024a) untersucht einen intensiven KLA während der HALO-(AC)³-Kampagne im Frühjahr 2022. Die praktizierte quasi-Lagrange’sche Flugstrategie erlaubt die Quantifizierung der diabatischen Erwärmung, Feuchteaufnahme und gleichzeitigen Wolkenentwicklung entlang des KLA. Durch den Vergleich von zwei Reanalysenprodukten mit den Beobachtungen werden Herausforderungen bei der Darstellung der Randeiszone, des turbulenten Wärmeflusses, sowie von Wolken- und Niederschlagsbildung aufgedeckt.
Abschließend wird die quasi-Lagrange’sche Auswertung auf die gesamte HALO-(AC)³-Kampagne ausgedehnt, was zu einem umfangreichen Datensatz von mehrfach beobachteten Luftmassen führt (Kirbus et al., 2024b,c). Ergebnisse aus Paper IV (Wendisch et al., 2024) geben einen statistischen Überblick über diese quasi-Lagrange’schen matches, sowie über diabatische Erwärmung/Abkühlung und Feuchtigkeitsänderungen innerhalb arktischer WLE und KLA.:Overview of Research Articles by Benjamin Kirbus
Contributions of Benjamin Kirbus to Papers I-IV
Supervision Statement
1 Air Mass Transformations in a Changing Arctic Climate System
1.1 Arctic Amplification
1.1.1 Arctic Climate Changes
1.1.2 Feedback Mechanisms
1.1.3 Role of Meridional Transport
1.2 Warm and Moist Air Intrusions
1.3 Marine Cold Air Outbreaks
1.4 Research Questions
2 Methods
2.1 Observations
2.1.1 Shipborne Measurements
2.1.2 Airborne Measurements
2.2 Trajectory Calculations
2.2.1 Eulerian versus Lagrangian Viewpoints
2.2.2 Trajectory Models
2.2.3 Challenges and Mitigation Strategies
2.3 Reanalysis Data
2.3.1 ERA5
2.3.2 CARRA
3 Results
3.1 Paper I – Pathways and Governing Processes of an Arctic WAI Observed
During MOSAiC
3.1.1 Motivation and Methods
3.1.2 Impacts at the MOSAiC Site
3.1.3 Investigation of Air Mass Pathways
3.2 Paper II – An Autumn CAO Forced by Surface Changes and Vertical Interactions
Through Advection in Higher Altitudes
3.2.1 Motivation and Methods
3.2.2 Thermodynamic and Cloud Evolution
3.2.3 Investigation of the Transformation Processes and Vertical Interactions
3.3 Paper III – Quasi-Lagrangian Thermodynamic and Cloud Evolution From Observations
Compared to Reanalyses
3.3.1 Motivation and Methods
3.3.2 Spatial Overview and Thermodynamic Profiles
3.3.3 Diabatic Heating and Moistening
3.4 Paper IV – Observed Diabatic Heating/Cooling and Moisture Changes During
All WAIs and CAOs of HALO-(AC)³
3.4.1 Motivation and Methods
3.4.2 Statistics on Matching Trajectories
3.4.3 Diabatic Heating/Cooling and Moisture Changes in WAIs and CAOs
4 Summary and Outlook
References
List of Abbreviations
List of Symbols
List of Figures
List of Tables
Acknowledgments
Curriculum Vitae
Appendix A: Paper I
Appendix B: Paper II
Appendix C: Paper III
Appendix D: Paper IVIn the last 30-40 years, the Arctic climate system has undergone dramatic changes. Phenomena like the rapid decline of Arctic sea ice and enhanced increase of near-surface air temperatures compared to the globe are key signatures of the Arctic amplification of climate change, caused by various local and remote feedback mechanisms. Poleward transport of latent heat, primarily through episodic warm and moist air intrusions (WAIs), has increased considerably. In opposite direction, marine cold air outbreaks (CAOs) denote the southward transport of cold and dry Arctic air masses. Both WAIs and CAOs have large impacts on the Arctic climate system, yet their accompanying air mass transformations are not fully understood and quantified. To investigate the mechanisms shaping WAIs and CAOs, this cumulative dissertation combines novel Lagrangian (air mass following) trajectory analysis with atmospheric reanalyses and observations from three recent Arctic expeditions.
In Paper I (Kirbus et al., 2023a), an intense WAI occurring in mid-April 2020 is analyzed. Measurements from the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition show a rapid rise of the 2-m air temperature by about 30K within two days, and an anomalous heating effect on the surface energy budget (SEB). A novel methodological approach is developed to investigate the air mass pathways during the WAI, tracing the evolution and transformation mechanisms of virtually all air masses ending above the MOSAiC site. The impact of the WAI on the SEB is investigated based on reanalysis data and observations both during the poleward drift, as well as at the MOSAiC site.
For Paper II (Kirbus et al., 2023b), a complex CAO occurring in autumn 2020 is explored, where the same air mass was first observed in the central Arctic during MOSAiC, and then two days later over the ice-free waters of Fram Strait as part of the MOSAiC Airborne observations in the Central Arctic (MOSAiC-ACA) campaign. The temporal evolution of the air mass is traced using reanalysis output, while reanalysis-derived temperature and humidity tendencies are utilized to explore the air mass transformations along the pathway. Contrary to expectations, the air mass transformations are not solely driven by surface changes from sea ice to open ocean, but also impacted by differential advection of clouds and water vapor across the near-surface flow. The relevance of wind shear and vertical interactions is therefore highlighted.
Paper III (Kirbus et al., 2024a) investigates a strong Arctic CAO observed during the HALO-(AC)³ campaign in spring 2022. For the first time, airborne observations gathered using a dedicated quasi-Lagrangian flight strategy enable a quantification of diabatic heating, moisture uptake, and concurrent cloud evolution along a CAO. By confronting two reanalysis products with the observations, their challenges with representing the marginal sea-ice zone, surface turbulent heat fluxes, clouds, and precipitation are revealed.
Finally, the quasi-Lagrangian analysis is extended to the whole HALO-(AC)³ campaign, resulting in a large dataset of matching air masses (Kirbus et al., 2024b,c). Paper IV (Wendisch et al., 2024) provides a statistical overview of these quasi-Lagrangian matches, as well as of diabatic heating/cooling and moisture changes within Arctic WAIs and CAOs.:Overview of Research Articles by Benjamin Kirbus
Contributions of Benjamin Kirbus to Papers I-IV
Supervision Statement
1 Air Mass Transformations in a Changing Arctic Climate System
1.1 Arctic Amplification
1.1.1 Arctic Climate Changes
1.1.2 Feedback Mechanisms
1.1.3 Role of Meridional Transport
1.2 Warm and Moist Air Intrusions
1.3 Marine Cold Air Outbreaks
1.4 Research Questions
2 Methods
2.1 Observations
2.1.1 Shipborne Measurements
2.1.2 Airborne Measurements
2.2 Trajectory Calculations
2.2.1 Eulerian versus Lagrangian Viewpoints
2.2.2 Trajectory Models
2.2.3 Challenges and Mitigation Strategies
2.3 Reanalysis Data
2.3.1 ERA5
2.3.2 CARRA
3 Results
3.1 Paper I – Pathways and Governing Processes of an Arctic WAI Observed
During MOSAiC
3.1.1 Motivation and Methods
3.1.2 Impacts at the MOSAiC Site
3.1.3 Investigation of Air Mass Pathways
3.2 Paper II – An Autumn CAO Forced by Surface Changes and Vertical Interactions
Through Advection in Higher Altitudes
3.2.1 Motivation and Methods
3.2.2 Thermodynamic and Cloud Evolution
3.2.3 Investigation of the Transformation Processes and Vertical Interactions
3.3 Paper III – Quasi-Lagrangian Thermodynamic and Cloud Evolution From Observations
Compared to Reanalyses
3.3.1 Motivation and Methods
3.3.2 Spatial Overview and Thermodynamic Profiles
3.3.3 Diabatic Heating and Moistening
3.4 Paper IV – Observed Diabatic Heating/Cooling and Moisture Changes During
All WAIs and CAOs of HALO-(AC)³
3.4.1 Motivation and Methods
3.4.2 Statistics on Matching Trajectories
3.4.3 Diabatic Heating/Cooling and Moisture Changes in WAIs and CAOs
4 Summary and Outlook
References
List of Abbreviations
List of Symbols
List of Figures
List of Tables
Acknowledgments
Curriculum Vitae
Appendix A: Paper I
Appendix B: Paper II
Appendix C: Paper III
Appendix D: Paper I
Lagrangian Studies of Arctic Air Mass Transformations During Warm Air Intrusions and Cold Air Outbreaks
No full textIn den letzten 30-40 Jahren hat sich das arktische Klimasystem dramatisch verändert. Phänomene wie der schnelle Rückgang des arktischen Meereises und die beschleunigte Zunahme der oberflächennahen Lufttemperaturen sind wesentliche Kennzeichen der arktischen Verstärkung des Klimawandels, verursacht durch verschiedene Rückkopplungsmechanismen. Der polwärts gerichtete Transport latenter Wärme, hauptsächlich durch Warmlufteinschübe (WLE), hat deutlich zugenommen. In entgegengesetzter Richtung bezeichnen marine Kaltluftausbrüche (KLA) den südwärts gerichteten Transport kalter und trockener arktischer Luftmassen. Sowohl WLE als auch KLA haben große Auswirkungen auf das arktische Klimasystem, doch ihre begleitenden Luftmassentransformationen sind noch nicht vollständig verstanden und quantifiziert. Um diese Lücke zu schließen, kombiniert diese kumulative Dissertation neuartige Lagrange’sche (Luftmassen-folgende) Trajektoranalysen mit atmosphärischen Reanalysen und Beobachtungen von drei kürzlich durchgeführten arktischen Expeditionen.
In Paper I (Kirbus et al., 2023a) wird ein WLE Mitte April 2020 analysiert. Messungen der Expedition Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) zeigen einen raschen Anstieg der 2-m Lufttemperatur um etwa 30K in zwei Tagen und einen anomalen Erwärmungseffekt auf das Energiebudget der Oberfläche. In einem neuen methodischen Ansatz wird die Entwicklung nahezu aller Luftmassen, welche über MOSAiC enden, sowie die relevanten Prozesse und Luftmassentransformationen ausgewertet.
Für Paper II (Kirbus et al., 2023b) wird ein komplexer KLA im Herbst 2020 erforscht. Die gleiche Luftmasse wurde zuerst in der Zentralarktis durch MOSAiC und zwei Tage später in der eisfreien Framstraße durch die Kampagne MOSAiC Airborne observations in the Central Arctic (MOSAiC-ACA) beobachtet. Eine atmosphärische Reanalyse wird genutzt, um die zeitliche Entwicklung der Luftmasse nachzuvollziehen. Darüber hinaus werden Temperatur- und Feuchtetendenzen genutzt, um die Luftmassentransformationen während des Drifts zu untersuchen. Entgegen der Erwartung werden diese Transformationen nicht nur durch Oberflächenveränderungen (Meereis zu offenem Ozean) beeinflusst, sondern auch durch differentielle Advektion von Wolken und Wasserdampf. Die Bedeutung von Windscherung und vertikaler Interaktionen wird hervorgehoben.
Paper III (Kirbus et al., 2024a) untersucht einen intensiven KLA während der HALO-(AC)³-Kampagne im Frühjahr 2022. Die praktizierte quasi-Lagrange’sche Flugstrategie erlaubt die Quantifizierung der diabatischen Erwärmung, Feuchteaufnahme und gleichzeitigen Wolkenentwicklung entlang des KLA. Durch den Vergleich von zwei Reanalysenprodukten mit den Beobachtungen werden Herausforderungen bei der Darstellung der Randeiszone, des turbulenten Wärmeflusses, sowie von Wolken- und Niederschlagsbildung aufgedeckt.
Abschließend wird die quasi-Lagrange’sche Auswertung auf die gesamte HALO-(AC)³-Kampagne ausgedehnt, was zu einem umfangreichen Datensatz von mehrfach beobachteten Luftmassen führt (Kirbus et al., 2024b,c). Ergebnisse aus Paper IV (Wendisch et al., 2024) geben einen statistischen Überblick über diese quasi-Lagrange’schen matches, sowie über diabatische Erwärmung/Abkühlung und Feuchtigkeitsänderungen innerhalb arktischer WLE und KLA.:Overview of Research Articles by Benjamin Kirbus
Contributions of Benjamin Kirbus to Papers I-IV
Supervision Statement
1 Air Mass Transformations in a Changing Arctic Climate System
1.1 Arctic Amplification
1.1.1 Arctic Climate Changes
1.1.2 Feedback Mechanisms
1.1.3 Role of Meridional Transport
1.2 Warm and Moist Air Intrusions
1.3 Marine Cold Air Outbreaks
1.4 Research Questions
2 Methods
2.1 Observations
2.1.1 Shipborne Measurements
2.1.2 Airborne Measurements
2.2 Trajectory Calculations
2.2.1 Eulerian versus Lagrangian Viewpoints
2.2.2 Trajectory Models
2.2.3 Challenges and Mitigation Strategies
2.3 Reanalysis Data
2.3.1 ERA5
2.3.2 CARRA
3 Results
3.1 Paper I – Pathways and Governing Processes of an Arctic WAI Observed
During MOSAiC
3.1.1 Motivation and Methods
3.1.2 Impacts at the MOSAiC Site
3.1.3 Investigation of Air Mass Pathways
3.2 Paper II – An Autumn CAO Forced by Surface Changes and Vertical Interactions
Through Advection in Higher Altitudes
3.2.1 Motivation and Methods
3.2.2 Thermodynamic and Cloud Evolution
3.2.3 Investigation of the Transformation Processes and Vertical Interactions
3.3 Paper III – Quasi-Lagrangian Thermodynamic and Cloud Evolution From Observations
Compared to Reanalyses
3.3.1 Motivation and Methods
3.3.2 Spatial Overview and Thermodynamic Profiles
3.3.3 Diabatic Heating and Moistening
3.4 Paper IV – Observed Diabatic Heating/Cooling and Moisture Changes During
All WAIs and CAOs of HALO-(AC)³
3.4.1 Motivation and Methods
3.4.2 Statistics on Matching Trajectories
3.4.3 Diabatic Heating/Cooling and Moisture Changes in WAIs and CAOs
4 Summary and Outlook
References
List of Abbreviations
List of Symbols
List of Figures
List of Tables
Acknowledgments
Curriculum Vitae
Appendix A: Paper I
Appendix B: Paper II
Appendix C: Paper III
Appendix D: Paper IVIn the last 30-40 years, the Arctic climate system has undergone dramatic changes. Phenomena like the rapid decline of Arctic sea ice and enhanced increase of near-surface air temperatures compared to the globe are key signatures of the Arctic amplification of climate change, caused by various local and remote feedback mechanisms. Poleward transport of latent heat, primarily through episodic warm and moist air intrusions (WAIs), has increased considerably. In opposite direction, marine cold air outbreaks (CAOs) denote the southward transport of cold and dry Arctic air masses. Both WAIs and CAOs have large impacts on the Arctic climate system, yet their accompanying air mass transformations are not fully understood and quantified. To investigate the mechanisms shaping WAIs and CAOs, this cumulative dissertation combines novel Lagrangian (air mass following) trajectory analysis with atmospheric reanalyses and observations from three recent Arctic expeditions.
In Paper I (Kirbus et al., 2023a), an intense WAI occurring in mid-April 2020 is analyzed. Measurements from the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition show a rapid rise of the 2-m air temperature by about 30K within two days, and an anomalous heating effect on the surface energy budget (SEB). A novel methodological approach is developed to investigate the air mass pathways during the WAI, tracing the evolution and transformation mechanisms of virtually all air masses ending above the MOSAiC site. The impact of the WAI on the SEB is investigated based on reanalysis data and observations both during the poleward drift, as well as at the MOSAiC site.
For Paper II (Kirbus et al., 2023b), a complex CAO occurring in autumn 2020 is explored, where the same air mass was first observed in the central Arctic during MOSAiC, and then two days later over the ice-free waters of Fram Strait as part of the MOSAiC Airborne observations in the Central Arctic (MOSAiC-ACA) campaign. The temporal evolution of the air mass is traced using reanalysis output, while reanalysis-derived temperature and humidity tendencies are utilized to explore the air mass transformations along the pathway. Contrary to expectations, the air mass transformations are not solely driven by surface changes from sea ice to open ocean, but also impacted by differential advection of clouds and water vapor across the near-surface flow. The relevance of wind shear and vertical interactions is therefore highlighted.
Paper III (Kirbus et al., 2024a) investigates a strong Arctic CAO observed during the HALO-(AC)³ campaign in spring 2022. For the first time, airborne observations gathered using a dedicated quasi-Lagrangian flight strategy enable a quantification of diabatic heating, moisture uptake, and concurrent cloud evolution along a CAO. By confronting two reanalysis products with the observations, their challenges with representing the marginal sea-ice zone, surface turbulent heat fluxes, clouds, and precipitation are revealed.
Finally, the quasi-Lagrangian analysis is extended to the whole HALO-(AC)³ campaign, resulting in a large dataset of matching air masses (Kirbus et al., 2024b,c). Paper IV (Wendisch et al., 2024) provides a statistical overview of these quasi-Lagrangian matches, as well as of diabatic heating/cooling and moisture changes within Arctic WAIs and CAOs.:Overview of Research Articles by Benjamin Kirbus
Contributions of Benjamin Kirbus to Papers I-IV
Supervision Statement
1 Air Mass Transformations in a Changing Arctic Climate System
1.1 Arctic Amplification
1.1.1 Arctic Climate Changes
1.1.2 Feedback Mechanisms
1.1.3 Role of Meridional Transport
1.2 Warm and Moist Air Intrusions
1.3 Marine Cold Air Outbreaks
1.4 Research Questions
2 Methods
2.1 Observations
2.1.1 Shipborne Measurements
2.1.2 Airborne Measurements
2.2 Trajectory Calculations
2.2.1 Eulerian versus Lagrangian Viewpoints
2.2.2 Trajectory Models
2.2.3 Challenges and Mitigation Strategies
2.3 Reanalysis Data
2.3.1 ERA5
2.3.2 CARRA
3 Results
3.1 Paper I – Pathways and Governing Processes of an Arctic WAI Observed
During MOSAiC
3.1.1 Motivation and Methods
3.1.2 Impacts at the MOSAiC Site
3.1.3 Investigation of Air Mass Pathways
3.2 Paper II – An Autumn CAO Forced by Surface Changes and Vertical Interactions
Through Advection in Higher Altitudes
3.2.1 Motivation and Methods
3.2.2 Thermodynamic and Cloud Evolution
3.2.3 Investigation of the Transformation Processes and Vertical Interactions
3.3 Paper III – Quasi-Lagrangian Thermodynamic and Cloud Evolution From Observations
Compared to Reanalyses
3.3.1 Motivation and Methods
3.3.2 Spatial Overview and Thermodynamic Profiles
3.3.3 Diabatic Heating and Moistening
3.4 Paper IV – Observed Diabatic Heating/Cooling and Moisture Changes During
All WAIs and CAOs of HALO-(AC)³
3.4.1 Motivation and Methods
3.4.2 Statistics on Matching Trajectories
3.4.3 Diabatic Heating/Cooling and Moisture Changes in WAIs and CAOs
4 Summary and Outlook
References
List of Abbreviations
List of Symbols
List of Figures
List of Tables
Acknowledgments
Curriculum Vitae
Appendix A: Paper I
Appendix B: Paper II
Appendix C: Paper III
Appendix D: Paper I
Lagrangian Studies of Arctic Air Mass Transformations During Warm Air Intrusions and Cold Air Outbreaks
No full textIn den letzten 30-40 Jahren hat sich das arktische Klimasystem dramatisch verändert. Phänomene wie der schnelle Rückgang des arktischen Meereises und die beschleunigte Zunahme der oberflächennahen Lufttemperaturen sind wesentliche Kennzeichen der arktischen Verstärkung des Klimawandels, verursacht durch verschiedene Rückkopplungsmechanismen. Der polwärts gerichtete Transport latenter Wärme, hauptsächlich durch Warmlufteinschübe (WLE), hat deutlich zugenommen. In entgegengesetzter Richtung bezeichnen marine Kaltluftausbrüche (KLA) den südwärts gerichteten Transport kalter und trockener arktischer Luftmassen. Sowohl WLE als auch KLA haben große Auswirkungen auf das arktische Klimasystem, doch ihre begleitenden Luftmassentransformationen sind noch nicht vollständig verstanden und quantifiziert. Um diese Lücke zu schließen, kombiniert diese kumulative Dissertation neuartige Lagrange’sche (Luftmassen-folgende) Trajektoranalysen mit atmosphärischen Reanalysen und Beobachtungen von drei kürzlich durchgeführten arktischen Expeditionen.
In Paper I (Kirbus et al., 2023a) wird ein WLE Mitte April 2020 analysiert. Messungen der Expedition Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) zeigen einen raschen Anstieg der 2-m Lufttemperatur um etwa 30K in zwei Tagen und einen anomalen Erwärmungseffekt auf das Energiebudget der Oberfläche. In einem neuen methodischen Ansatz wird die Entwicklung nahezu aller Luftmassen, welche über MOSAiC enden, sowie die relevanten Prozesse und Luftmassentransformationen ausgewertet.
Für Paper II (Kirbus et al., 2023b) wird ein komplexer KLA im Herbst 2020 erforscht. Die gleiche Luftmasse wurde zuerst in der Zentralarktis durch MOSAiC und zwei Tage später in der eisfreien Framstraße durch die Kampagne MOSAiC Airborne observations in the Central Arctic (MOSAiC-ACA) beobachtet. Eine atmosphärische Reanalyse wird genutzt, um die zeitliche Entwicklung der Luftmasse nachzuvollziehen. Darüber hinaus werden Temperatur- und Feuchtetendenzen genutzt, um die Luftmassentransformationen während des Drifts zu untersuchen. Entgegen der Erwartung werden diese Transformationen nicht nur durch Oberflächenveränderungen (Meereis zu offenem Ozean) beeinflusst, sondern auch durch differentielle Advektion von Wolken und Wasserdampf. Die Bedeutung von Windscherung und vertikaler Interaktionen wird hervorgehoben.
Paper III (Kirbus et al., 2024a) untersucht einen intensiven KLA während der HALO-(AC)³-Kampagne im Frühjahr 2022. Die praktizierte quasi-Lagrange’sche Flugstrategie erlaubt die Quantifizierung der diabatischen Erwärmung, Feuchteaufnahme und gleichzeitigen Wolkenentwicklung entlang des KLA. Durch den Vergleich von zwei Reanalysenprodukten mit den Beobachtungen werden Herausforderungen bei der Darstellung der Randeiszone, des turbulenten Wärmeflusses, sowie von Wolken- und Niederschlagsbildung aufgedeckt.
Abschließend wird die quasi-Lagrange’sche Auswertung auf die gesamte HALO-(AC)³-Kampagne ausgedehnt, was zu einem umfangreichen Datensatz von mehrfach beobachteten Luftmassen führt (Kirbus et al., 2024b,c). Ergebnisse aus Paper IV (Wendisch et al., 2024) geben einen statistischen Überblick über diese quasi-Lagrange’schen matches, sowie über diabatische Erwärmung/Abkühlung und Feuchtigkeitsänderungen innerhalb arktischer WLE und KLA.:Overview of Research Articles by Benjamin Kirbus
Contributions of Benjamin Kirbus to Papers I-IV
Supervision Statement
1 Air Mass Transformations in a Changing Arctic Climate System
1.1 Arctic Amplification
1.1.1 Arctic Climate Changes
1.1.2 Feedback Mechanisms
1.1.3 Role of Meridional Transport
1.2 Warm and Moist Air Intrusions
1.3 Marine Cold Air Outbreaks
1.4 Research Questions
2 Methods
2.1 Observations
2.1.1 Shipborne Measurements
2.1.2 Airborne Measurements
2.2 Trajectory Calculations
2.2.1 Eulerian versus Lagrangian Viewpoints
2.2.2 Trajectory Models
2.2.3 Challenges and Mitigation Strategies
2.3 Reanalysis Data
2.3.1 ERA5
2.3.2 CARRA
3 Results
3.1 Paper I – Pathways and Governing Processes of an Arctic WAI Observed
During MOSAiC
3.1.1 Motivation and Methods
3.1.2 Impacts at the MOSAiC Site
3.1.3 Investigation of Air Mass Pathways
3.2 Paper II – An Autumn CAO Forced by Surface Changes and Vertical Interactions
Through Advection in Higher Altitudes
3.2.1 Motivation and Methods
3.2.2 Thermodynamic and Cloud Evolution
3.2.3 Investigation of the Transformation Processes and Vertical Interactions
3.3 Paper III – Quasi-Lagrangian Thermodynamic and Cloud Evolution From Observations
Compared to Reanalyses
3.3.1 Motivation and Methods
3.3.2 Spatial Overview and Thermodynamic Profiles
3.3.3 Diabatic Heating and Moistening
3.4 Paper IV – Observed Diabatic Heating/Cooling and Moisture Changes During
All WAIs and CAOs of HALO-(AC)³
3.4.1 Motivation and Methods
3.4.2 Statistics on Matching Trajectories
3.4.3 Diabatic Heating/Cooling and Moisture Changes in WAIs and CAOs
4 Summary and Outlook
References
List of Abbreviations
List of Symbols
List of Figures
List of Tables
Acknowledgments
Curriculum Vitae
Appendix A: Paper I
Appendix B: Paper II
Appendix C: Paper III
Appendix D: Paper IVIn the last 30-40 years, the Arctic climate system has undergone dramatic changes. Phenomena like the rapid decline of Arctic sea ice and enhanced increase of near-surface air temperatures compared to the globe are key signatures of the Arctic amplification of climate change, caused by various local and remote feedback mechanisms. Poleward transport of latent heat, primarily through episodic warm and moist air intrusions (WAIs), has increased considerably. In opposite direction, marine cold air outbreaks (CAOs) denote the southward transport of cold and dry Arctic air masses. Both WAIs and CAOs have large impacts on the Arctic climate system, yet their accompanying air mass transformations are not fully understood and quantified. To investigate the mechanisms shaping WAIs and CAOs, this cumulative dissertation combines novel Lagrangian (air mass following) trajectory analysis with atmospheric reanalyses and observations from three recent Arctic expeditions.
In Paper I (Kirbus et al., 2023a), an intense WAI occurring in mid-April 2020 is analyzed. Measurements from the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition show a rapid rise of the 2-m air temperature by about 30K within two days, and an anomalous heating effect on the surface energy budget (SEB). A novel methodological approach is developed to investigate the air mass pathways during the WAI, tracing the evolution and transformation mechanisms of virtually all air masses ending above the MOSAiC site. The impact of the WAI on the SEB is investigated based on reanalysis data and observations both during the poleward drift, as well as at the MOSAiC site.
For Paper II (Kirbus et al., 2023b), a complex CAO occurring in autumn 2020 is explored, where the same air mass was first observed in the central Arctic during MOSAiC, and then two days later over the ice-free waters of Fram Strait as part of the MOSAiC Airborne observations in the Central Arctic (MOSAiC-ACA) campaign. The temporal evolution of the air mass is traced using reanalysis output, while reanalysis-derived temperature and humidity tendencies are utilized to explore the air mass transformations along the pathway. Contrary to expectations, the air mass transformations are not solely driven by surface changes from sea ice to open ocean, but also impacted by differential advection of clouds and water vapor across the near-surface flow. The relevance of wind shear and vertical interactions is therefore highlighted.
Paper III (Kirbus et al., 2024a) investigates a strong Arctic CAO observed during the HALO-(AC)³ campaign in spring 2022. For the first time, airborne observations gathered using a dedicated quasi-Lagrangian flight strategy enable a quantification of diabatic heating, moisture uptake, and concurrent cloud evolution along a CAO. By confronting two reanalysis products with the observations, their challenges with representing the marginal sea-ice zone, surface turbulent heat fluxes, clouds, and precipitation are revealed.
Finally, the quasi-Lagrangian analysis is extended to the whole HALO-(AC)³ campaign, resulting in a large dataset of matching air masses (Kirbus et al., 2024b,c). Paper IV (Wendisch et al., 2024) provides a statistical overview of these quasi-Lagrangian matches, as well as of diabatic heating/cooling and moisture changes within Arctic WAIs and CAOs.:Overview of Research Articles by Benjamin Kirbus
Contributions of Benjamin Kirbus to Papers I-IV
Supervision Statement
1 Air Mass Transformations in a Changing Arctic Climate System
1.1 Arctic Amplification
1.1.1 Arctic Climate Changes
1.1.2 Feedback Mechanisms
1.1.3 Role of Meridional Transport
1.2 Warm and Moist Air Intrusions
1.3 Marine Cold Air Outbreaks
1.4 Research Questions
2 Methods
2.1 Observations
2.1.1 Shipborne Measurements
2.1.2 Airborne Measurements
2.2 Trajectory Calculations
2.2.1 Eulerian versus Lagrangian Viewpoints
2.2.2 Trajectory Models
2.2.3 Challenges and Mitigation Strategies
2.3 Reanalysis Data
2.3.1 ERA5
2.3.2 CARRA
3 Results
3.1 Paper I – Pathways and Governing Processes of an Arctic WAI Observed
During MOSAiC
3.1.1 Motivation and Methods
3.1.2 Impacts at the MOSAiC Site
3.1.3 Investigation of Air Mass Pathways
3.2 Paper II – An Autumn CAO Forced by Surface Changes and Vertical Interactions
Through Advection in Higher Altitudes
3.2.1 Motivation and Methods
3.2.2 Thermodynamic and Cloud Evolution
3.2.3 Investigation of the Transformation Processes and Vertical Interactions
3.3 Paper III – Quasi-Lagrangian Thermodynamic and Cloud Evolution From Observations
Compared to Reanalyses
3.3.1 Motivation and Methods
3.3.2 Spatial Overview and Thermodynamic Profiles
3.3.3 Diabatic Heating and Moistening
3.4 Paper IV – Observed Diabatic Heating/Cooling and Moisture Changes During
All WAIs and CAOs of HALO-(AC)³
3.4.1 Motivation and Methods
3.4.2 Statistics on Matching Trajectories
3.4.3 Diabatic Heating/Cooling and Moisture Changes in WAIs and CAOs
4 Summary and Outlook
References
List of Abbreviations
List of Symbols
List of Figures
List of Tables
Acknowledgments
Curriculum Vitae
Appendix A: Paper I
Appendix B: Paper II
Appendix C: Paper III
Appendix D: Paper I
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