Bachelor/Masterarbeit
Characterization of Cirrus Clouds over Cabo Verde by means of Polarization Lidar Measurements
Ausschreibungsdatum: 25.08.2025
Zirruswolken bestehen aus Eiskristallen, welche homogen (aus Lösungströpfchen) oder heterogen (auf einem Aerosolpartikel) gebildet werden können. Die spezielle Form der Eiskristalle führt dazu, dass sie Licht depolarisieren. Diese Eigenschaft nutzt man mit einem Polarisationslidar aus, um Zirruswolken zu detektieren. Seit Juni 2021 betreibt das TROPOS ein solches Lidargerät in Mindelo auf den Kapverden (siehe Foto), welches das Depolarisationsverhältnis bei 3 Wellenlängen misst. Das Ziel der Masterarbeit ist es, diese Polarisationsmessungen auszunutzen, um so mehr Informationen über die Form, vertikale Struktur und den Bildungsmechanismus der tropischen Zirren zu erforschen.
Kontakt: Moritz Haarig, haarig[at]tropos.de
Eis-Multiplikation – Welche Mechanismen in Wolken können potentiell zur sekundären Erhöhung der Eiskristallanzahl beitragen?
Ausscheibungsdatum: 21.05.2024
In Mischphasenwolken (bestehend aus Eiskristallen und unterkühlten flüssigen Tröpfchen) können mehr Eiskristalle vorhanden sein als durch das bloße Gefrieren flüssiger Tröpfchen erwartbar wäre. In den letzten Jahren wurden verschiedene Mechanismen zur Erklärung des Phänomens vorgeschlagen. Die Gesamtheit dieser Prozesse wird als Eismultiplikation (engl. ‚ice multiplication‘ oder auch ‚secondary ice production’) bezeichnet. Vorstellbar sind zum Beispiel Kollisionen zwischen zwei Eiskristallen oder das Zerbrechen gefrierender Tropfen, bei denen kleinere Eissplitter entstehen und somit mehr Eispartikel vorhanden sind als vorher.
Das Ziel der angebotenen Arbeit ist, die Bedeutung der Eismultiplikation auf Wolkeneigenschaften abzuschätzen. Dafür soll zunächst ein kurzer Überblick über die in der Fachliteratur vorgeschlagenen Prozesse der Eismultiplikation erstellt werden. Basierend darauf sollen diese Prozesse dann auf bestehende simulierte Wolkeneigenschaften (Wolkentropfen- und Eiskristallgrößenverteilungen) eines Wolkenmikrophysikmodells angewendet werden. Dem können auch eigene Simulationen mit einer idealisierten Version dieses Modells hinzugefügt werden. Die Arbeit bietet einen Einstieg in mikrophysikalische Prozesse in Wolken und deren Beschreibung für z. B. Wettermodelle. Kenntnisse von Python, R, o.Ä. sind für die Datenanalyse notwendig.
Kontakt:
Dr. Roland Schrödner, Tel.: +49 (0)341 2717 7388, eMail: roland.schroedner[at]tropos.de
Masterarbeiten
How Clouds and Aerosols Modulate the Radiation Balance over Cape Verde
Date of announcement: 07 October 2025
What influences the radiation balance in Mindelo (e.g. Island effects, desert dust, cloud regime)? This question will be addressed by analyzing broadband and spectral aerosol and cloud radiative effects with a focus on radiation closure
studies at Mindelo (Cape Verde) ACTRIS station, using new geostationary satellite (MTG) and reference surface observations.
The study includes:
• Cloud and aerosol cases selected from the novel Flexible Combined Imager (FCI) onboard MTG.
• Use of radiation transfer forward model for spectral and broadband simulations with input from surface observations (e.g., Cloudnet including cloud radar, lidar and microwave radiometer)
• Radiative closure with model simulation, and satellite and surface observations for validation.
• First comparisons with new EarthCARE radiation products.
Contact: Prof. Dr. Andreas Macke, macke[at]tropos.de or Jonas Witthuhn (witthuhn@tropos.de), Sebastian Bley (bley@tropos.de), Anja Hünerbein (anjah@tropos.de)
Investigating the optical properties of marine aerosol using the
EarthCARE satellite
Date of announcement: 07 October 2025
With the recently
launched EarthCARE satellite mission, having a high-spectralresolution lidar on board, the optical properties of marine aerosol can be studies for the first time based on backscatter, extinction,
and depolarization measurements even in very remote locations, like for example the Southern oceans.
In this work, the regional and seasonal patterns of the optical properties of marine aerosol will be investigated using data from the EarthCARE satellite. The analysis can cover several predefined regions, e.g., representing all seas and oceans, which can be defined further during the course of the ongoing work.
Contact: Dr. Athena A. Floutsi, floutsi[at]tropos.de or Dr. Holger Baars, baars@tropos.de
EarthCARE observations of wildfire smoke
Date of announcement: 25 August 2025
The new satellite EarthCARE launched in May 2024 carries an advanced atmospheric lidar (ATLID) which is perfectly suited to study the elevated smoke plumes on a global scale. It provides layer heights and optical properties of the smoke plumes. We have observed that large parts of the Arctic are filled with smoke since June 2025.
The topic of the master thesis is use EarthCARE to study the occurrence, lofting and removal processes of the smoke plumes. Furthermore, the interaction of the smoke layers with cirrus clouds is of great interest.
Contact: Moritz Haarig, haarig[at]tropos.de
Characterization of the atmosphere above Antarctica by means of ground-based remote sensing
Date of announcement: 25.02.25
The Antarctic continent and its surrounding Southern Ocean are key components of the global climate system. In the framework of the field experiment, continuous Observations of Aerosol-Cloud-Interaction in Antarctica (COALA), novel observations of aerosol and clouds by means of ground-based remote sensing have been performed by TROPOS in Antarctica at the German Neumayer Station III (70.67°S, 8.27°W) from January to December 2023. The deployment of the OCEANET-Atmosphere remote-sensing observatory covers the full ACTRIS aerosol and cloud profiling capabilities additionally to meteorological, radiation, and air chemistry in-situ observations at the Antarctic station.
The master thesis shall focus on microphysical properties of (shallow) mixed-phase clouds retrieved from lidar and radar synergy. Depending on the student’s interest, the topic can be developed towards, e.g., characterizing the aerosol properties relevant for cloud formation or intercomparison with reanalysis datasets among other possibilities including sensor synergy.
Contact: Dr. Martin Radenz, TROPOS (radenz@tropos.de), Dr. Holger Baars, TROPOS (baars@tropos.de)
Assessing humidity growth effects of different aerosol types using
ground-based Raman lidar observations
Ausschreibungsdatum: 01.09.2024
Hygroscopic growth and shrinkage processes change the size, refractive
index, and partly also the shape of aerosol particles and thus also their
optical, radiative and nucleating properties (e.g., Haarig et al., 2017).
PollyXT Raman lidars (Engelmann et al., 2016) have the capability to
measure water vapor mixing ratio (e.g., Dai et al., 2018). Simultaneous
profiling of water vapor mixing ratio and particle optical properties
allow to study aerosol hygroscopicity (e.g., Althausen et al., 2020;
Navas-Guzmán et al., 2019). For calibration and calculation of relative
humidity, the use of radiosonde, model, and microwave radiometer data
can be intercompared. Data from PollyNET (Baars et al., 2016), a
network of PollyXT lidars, from contrasting stations with different
aerosol and humidity conditions like Germany, Cabo Verde, Cyprus, and
Tajikistan shall be used.
Kontakt: Julian Hofer, hofer[at]tropos.de
Profile intercomparison of CCN datasets retrieved from ground-based
lidars, aerosol model reanalysis and spaceborne lidar
Ausschreibungsdatum: 01.09.2024
Vertical profiles of microphysical and cloud-relevant aerosol properties
such as cloud condensation nuclei (CCN) concentration can be estimated
using polarization lidar techniques (e.g., Mamouri and Ansmann, 2016).
Global CCN datasets retrieved from the spaceborne lidar CALIPSOCALIOP
(Choudhury and Tesche, 2022; 2023) and the aerosol model
reanalysis CAMS (Block et al., 2024), which became available recently
and are already used for comparison studies (e.g., Choudhury et al.,
2024), can be intercompared with retrievals from PollyNET (Baars et al.,
2016), a network of ground-based PollyXT polarization Raman lidars
(Engelmann et al., 2016), at multiple, contrasting stations like Germany,
Cabo Verde, Cyprus, and Tajikistan. Identifying similarities and
differences between the ground-based and spaceborne-lidar-derived
CCN datasets may improve the underlying retrieval methods and
ultimately the understanding and quantification of aerosol-cloudinteraction.
Kontakt: Julian Hofer, hofer[at]tropos.de