Themen für Bachelor/Masterarbeiten
Die Gruppe Atmosphärische Dynamik bietet ein breites Spektrum an Bachelor- und Masterthemen in den Bereichen Dynamik der Atmosphäre, numerische Analysen und Vorhersage auf vielen Zeitskalen. Die Themen leiten sich aus den aktuellen Forschungsinteressen der Gruppe ab, die folgende miteinander verbundene Themen umfassen, die für die moderne Meteorologie von zentraler Bedeutung sind:
- Wellen in der Atmosphäre und ihre Rolle bei der Klimadynamik
- Klimamodellierung und Klimawandel
- Extreme Wetterereignisse
- Energiekreislauf der Erde und Energietransporte in der Atmosphäre
- Strukturen der großräumigen Zirkulation
- Vorhersagbarkeit, Modellfehler und systematische Fehler
- Mathematische Aspekte der atmosphärischen Dynamik
In unserer Arbeit kombinieren wir statistische Methoden und neuartige diagnostische Ansätze. Typischerweise basiert die MS / Ba-Forschung auf Beobachtungs- und Analysedaten und einer Hierarchie numerischer Modelle, deren Komplexität von Spielzeugmodellen bis zu vollständigen Klimamodellen reicht. Für mathematisch interessierte Studenten gibt es eine Reihe von Problemen, die Meteorologie mit Geometrie, Analyse und Statistik verbinden. Nachfolgend finden Sie eine unvollständige Liste der vorgeschlagenen Themen für Masterarbeiten. Andere Themenvorschläge und Ihre Ideen sind willkommen.
Bachelor topics/Bachelor-Arbeiten (Richard Blender):
Extremereignisse in Daten und Modellen
Das öffentliche Interesse an meteorologischen Ereignissen konzentriert sich größtenteils auf besonders extreme Phänomene, die mit entsprechenden Schäden verbunden sind. Statistisch gesehen sind dies sehr große Abweichungen vom Normalzustand, wie zum Beispiel starke Winde, hohe oder niedrige Temperaturen und intensive Niederschläge. Werden zusätzlich Zeitskalen berücksichtigt ergibt sich eine Fülle von möglichen Schadensursachen. Angeboten werden Bachelor-Arbeiten, in denen die statistischen Eigenschaften von Extremen berechnet werden und eventuell Zusammenhänge mit externen Einflussgrößen abgeschätzt werden.
Zyklonenzugbahnen in den mittleren Breiten
Die Zyklonen in den mittleren Breiten sind zum Teil mit sehr starken Niederschlägen und Stürmen verbunden. Gleichzeitig sind ihre Schwankungen für die natürliche Klimavariabilität in den mittleren Breiten verantwortlich. Die Zugbahnen werden durch großskalige Bedingungen beeinflusst und ändern sich unter Umständen in einem wärmeren Klima. In den Bachelor-Arbeiten werden Zugbahnen in vorhandenen Daten bestimmt und statistische Eigenschaften wie räumliche Verteilungen, zeitliche Korrelationen und großräumige Zusammenhänge.
Klimavariabilität auf langen Zeitskalen
Klimaschwankungen werden auf Zeitskalen von Jahrzehnten bis zu vielen Jahrtausenden gefunden. Ursachen dieser Schwankungen sind in der Regel in Kompartments zu suchen, die Prozesse auf den entsprechenden Zeitskalen aufweisen. Die Kenntnis dieser Variabilitäten ist entscheidend zur Beurteilung von anthropogenen Klimaänderungen. Klimamodelle sollten beobachtete Schwankungen wiedergeben können.
Master topics/Master-Arbeiten
1. Interaction of inertia-gravity waves and the balanced flow on the sphere
Inertia-gravity waves appear at many scales in the atmosphere and ocean. In the extratropics, inertia-gravity waves (IG) are important ingredient of subsynoptic dynamics and they are generated by the interaction of the flow with orography, by surface and boundary layer processes, by tropospheric moist convection and by imbalance of synoptic jets. In the tropics, the primary source of IG waves is the convective heating and tropical IG waves appear at all spatial scales. In this project, we shall employ a new numerical model to study interactions between the propagating IG waves and the background balanced flow. The model solves global nonlinear shallow-water equations on the sphere for the IG and Rossby wave amplitudes.
Supervisors: Sergyiy Vasylkevych and Nedjeljka Žagar
2. Equatorial waves and the Rossby wave source
Two wave solutions exist near the equator that are absent in the extratropical atmosphere: the Kelvin wave (KW) and mixed Rossby-gravity (MRG) waves. These waves fill the frequency gap between the Rossby and inertia-gravity waves that is present in the midlatitudes. Depending on their vertical scale and the zonal wavenumber, the MRG and Kelvin waves have characteristics similar to either equatorial Rossby or inertia-gravity waves. Excited by latent heat release in deep tropical convection, they propagate through the equatorial waveguide, communicate effects of the heat sources far away along the equator and through their vertical energy and momentum transport they play an important role for the general circulation. In this project, we shall perform numerical simulations to quantify the contributions of these waves to the anomalous vorticity sources in the subtropics.
Supervisors: Nedjeljka Žagar and Frank Lunkeit
3. Where is the central latitude of ITCZ?
The Glossary of the American Meteorological Society defines the intertropical convergence zone (ITCZ) as “an axis, or a portion thereof, of the broad trade wind current of the Tropics. The axis is the dividing line between the southeast trades and the northeast trades and it is collocated with the ascending branch of the Hadley cell.” In research practice the ITCZ has usually been defined by the narrow belt of (proxy) observations of deep tropical convection, i.e., by the location of precipitation maxima above a certain threshold, by the surface wind convergence or by the zero crossing of the average meridional wind in the boundary layer. In this master thesis we will estimate the central latitude of ITCZ by evaluating the vertical velocity associated with the horizontal wind convergence in reanalysis data and its comparison with the precipitation maxima. Collocation properties of precipitation maxima and the latitude of strongest vertical motions will be discussed for different land and ocean regions.
Supervisor: Nedjeljka Zagar
4. Growth of forecast errors in the tropics
Many studies of the growth of errors in forecasts have focused on the quasi-geostrophic dynamics and often considered the error-free large-scale initial state. In contrast, the global operational numerical weather prediction and ensemble prediction systems are characterized by significant analysis uncertainties at large scales, especially in the tropics. In fact, data suggests that the larger the scale, the greater the initial uncertainties. In this project, we shall employ a simplified numerical model to study how initial state errors in inertia-gravity wave component of the tropical circulation affect the growth of forecast errors.
Supervisors: Nedjeljka Žagar and Sergiy Vasylkevych
5. Rossby wave variability
General circulation models (GCMs) simulate the spectrum of variability from weather to decadal time scales across many spatial scales. Temporal variability can be split among various time scales, variables and regions whereas details of the spatial spectrum associated with certain temporal frequency can be described as a combination of “preferred” patterns. Using the MODES (https://modes.cen.uni-hamburg.de) decomposition of reanalyses and climate model simulations into many scales, we shall investigate horizontal and vertical shifts in weather patterns - Rossby wave variability in midlatitudes.
Supervisor: Nedjeljka Žagar
6. Modelling the climate of Amasia
On very long time scales, continental drift effects the Earth and its climate system together with changes in the orbital parameters, etc. Recently it has been speculated that a supercontinent (Amasia) will form
over the North Pole in about 50 to 200 million years (Nature 482, 208-211, 2012). This project will use a climate model of intermediate complexity (PlaSim) to analyse the climate system of this future planet
Earth. The work will focus on particular aspects depending on the
interest of the student.
Supervisor: Frank Lunkeit
7. Sensitivity of tropical wave circulation to cumulus parameterization
Atmospheric circulation, tropical waves, cumulus parameterizations
The parameterization of moist (cumulus) convection is a crucial part of climate models. Various schemes have been proposed based on assumptions made about the dominant mechanisms. The particular choice of the parameterization scheme may have a significant effect on the simulated climate, in particular on the characteristics of tropical waves. This project will use a climate model of intermediate complexity (PlaSim) in an idealized setup to compare the effect of different cumulus parameterization schemes on tropical waves. A diagnostic Tool (MODES, https://modes.cen.uni-hamburg.de) will be applied to decompose the circulation, and to analyse the contribution of different wave types.
Supervisors: Frank Lunkeit and Nedjeljka Žagar
8. Understanding North Atlantic midwinter suppression in state-of-the-art climate simulations
We propose here a model study of the midwinter suppression in the Northern Atlantic, analysing an ensemble of CMIP model simulations over the historical period. We will first verify the existence of the relatively well understood Pacific midwinter suppression, comparing several indices of baroclinic activity in the mid-latitudinal storm track belt and studying the relation with the seasonality of Arctic and subptropical tropospheric temperatures. With this knowledge, we will focus on the North Atlantic sector, to assess whether the suppression exists in models and if the mechanisms of suppression are comparable with the Northern Pacific. We will then adopt a similar analysis on the study of future climate projections, after carefully selecting the models that better sample this mode of variability.
Supervisors: Richard Blender
9. Wie verbessern Aeolus-Beobachtungen die globalen Wettervorhersagen?
Masterthemen werden in Bezug auf den Aeolus-Satelliten angeboten, die erste Satellitenmission, die die globalen Windprofile misst, https://www.esa.int/Applications/Observing_the_Earth/Aeolus.
Der Satellit wurde am 22. August 2018 gestartet und seine Beobachtungen tragen bereits zu globalen Wettervorhersagen bei. DWD und EZMW verwenden Daten operativ und haben einen positiven Einfluss von Aeolus auf die Ausgangsbedingungen für Wettervorhersagen (Analysen) und auf die Vorhersagen gezeigt. Der Effekt war in den letzten Monaten besonders wichtig, da die Windbeobachtungen von Flugzeugen stark eingeschränkt wurden.
Wir laden die Studenten ein, sich an der laufenden Arbeit zu beteiligen, um zu verstehen, wie Aeolus die Darstellung verschiedener Prozesse in Wetteranalysen und -vorhersagen verbessert.
Betreuerin: Nedjeljka Žagar
10. Stratospheric gravity waves in ICON
Compared to the troposphere, the midlatitude stratosphere may appear almost boring; it is statically stable i.e. instability processes are hardly known, and water vapour is present only in traces. Yet, a large body of evidence shows that stratospheric dynamics affect the surface weather within a few weeks, though exact mechanisms are poorly understood.
The troposphere and stratosphere communicate through both Rossby and gravity waves. This master thesis proposal focuses on the propagation of resolved stratospheric gravity waves in ICON simulations. Recent research has shown that stratospheric gravity waves may be excited within the stratosphere due to the lateral shear of the horizontal wind within the polar vortex.
The student will compare gravity wave propagation in simulations initialised with and without tropospheric gravity wave sources and compare their vertical and horizontal propagation. The research question is the origin of gravity waves and the effect of the background flow on the wave propagation.
Work Location: MPI-M
Supervisors: Claudia Stephan( claudia.stephan"AT"mpimet.mpg.de) (MPI-M), Nedjeljka Žagar