Characterization of Cirrus Clouds over Cabo Verde by means of Polarization Lidar Measurements
Date of announcement: 09.01.2024
Cirrus clouds consist of ice crystals, which can be formed homogeneously (from solution droplets) or heterogeneously (on an aerosol particle). The special shape of the ice crystals causes them to depolarize light. This property is exploited with a polarization lidar to detect cirrus clouds.
Since June 2021, TROPOS has been operating such a lidar device in Mindelo on Cape Verde (see picture), which measures the depolarization ratio at 3 wavelengths. The aim of the master's thesis is to exploit the polarization measurements to obtain more information about the shape, vertical structure and formation mechanism of tropical cirrus clouds.
Contact: Moritz Haarig, haarig[at]tropos.de
Ice Multiplication - What processes in clouds can potentially contribute to the secondary increase in ice crystal number?
Date of Announcement: 09.01.2024
In mixed-phase clouds (consisting of ice crystals and supercooled liquid droplets), more ice crystals may be present than would be expected from the primary freezing of liquid droplets. In recent years, several processes have been proposed to explain the phenomenon. These processes together are called ice multiplication or secondary ice production. Possible mechanisms are for example collisions between two ice crystals or the breaking of freezing drops, where smaller ice splinters are produced and thus more ice particles are present than before.
The aim of the offered thesis is to assess the significance of ice multiplication on cloud properties. First, a brief overview of the ice multiplication processes proposed in the literature needs to be provided. Based on this, these processes will then be applied to existing simulated cloud properties (cloud droplet and ice crystal size distributions) of a cloud microphysics model. Own simulations with an idealized version of this model can (Bachelor thesis) or will (Master thesis) be be added. The work provides an introduction to microphysical processes in clouds and their description for e.g. weather models. Knowledge of Python, R, etc. is necessary for data analysis.
Contact:
Dr. Roland Schrödner, Tel.: +49 (0)341 2717 7388, eMail: roland.schroedner[at]tropos.de
Analyse von Extremwerten in der UV-Strahlung auf Basis von Beobachtungen in Melpitz
Ausschreibungsdatum 10.01.2024
Die solare UV-Strahlung ist der energiereichste Teil im Spektrum der Sonnenstrahlung und hat einen starken Einfluss auf den Menschen und die Umwelt. Die am Boden einfallende UV-Strahlung wird in Deutschland seit einigen Jahren in einem Messnetz erfasst, zu dem TROPOS durch Messungen an seiner Forschungsstation Melpitz beiträgt. Das Ziel der Arbeit ist es, die zeitlich hochaufgelösten Messungen zu analysieren und statistische Kenngrößen zur Beschreibung der Messungen abzuleiten. Ein möglicher Schwerpunkt der Arbeit kann die Untersuchung von Extremwerten in der Strahlung in Situationen mit durchbrochener Bewölkung sein. Es sollen Kenngrößen identifiziert und genutzt werden, um vergleichbare Situationen zu klassifizieren (z.B. wolkenfreie Fälle, durchbrochene Bewölkung). Die Beobachtungen sollen auch mit Prognosen des UV-Index vom DWD verglichen werden.
Kontakt:
Dr. Rico Hengst, TROPOS, E-Mail: hengst[at]tropos.de, Telefon: 0341-2717-7168
Sensitivity of Tropical Cyclones to Cloud Microphysics
Date of announcement: 05.01.2024
Tropical cyclones potentially intensity in future as the climate warms, however, significant uncertainties remain. In the proposed work, the development of tropical cyclones is investigated using convection-permitting simulations with the ICON model combined together with satellite observations. The choice of the cloud microphysics scheme plays an important role for the simulation of tropical cyclones because it controls the phase partitioning within the cloud bands and thus the pathways for precipitation formation. Some indications exist that more sophisticated cloud microphysical descriptions can also lead to better topical cyclone forecasts.
Contact: Dr. Fabian Senf, TROPOS, senf@tropos.de, phone: 0341 2717 7170