# Current students

On this page, the current GeoSim students present their projects.

## RA I, Solid Earth

### Felix Hoffmann (formerly Eckelmann)

**Education**

MSc in GeoScience (2013) at the University of Potsdam. Thesis title: 'Recent crustal deformation in the orogenic pateau interior: InSAR observations from the Salar de Pocitos, NW Argentina'.

**Current project with GeoSim (since 01.10.13) **

The preliminary title of my PhD thesis is ‘Deformation patterns related to the seismic cycle in the Central Andes using geodetic data.’ I am working at the GFZ Potsdam, section 3.1 Lithosphere Dynamics.

Supervisor: Prof. Dr. Onno Oncken (GFZ)

The western coast of the South American continent is dominated by the subduction of the Nazca plate. This special tectonic regime causes a high seismic and also volcanic activity with huge megathrust earthquake events of magnitudes of Mw=8 and even larger. In order to improve the knowledge about the tectonic mechanisms behind these events my goal is to apply different geodetic methods as GPS and InSAR in the northern part of Chile and northern Argentina. I will investigate regions at different stages of the seismic cycle and analyze especially the inter- and post-seismic behaviour of the crustal deformation.

### Stefan Rüdrich

**Education**

MSc in Mathematics (2012) at Freie Universität Berlin. Majors: Discrete Mathematics, Stochastic Dynamics. Thesis title: 'Identification of clusters in graphs - non-spectral methods, the random walk approach and their generalization to directed graphs'

**Current project with GeoSim (since 15.01.2013)**

'Metastability in Time Series Analysis' at the Department of Mathematics and Computer Science, Freie Universität Berlin.

Supervisors: Christof Schütte (FU Mathematics) and Sebastian Hainzl (GFZ 2.1).

To analyze and forecast geoscientific processes, methods of network analyses are widely used, exploiting the relation between metastable substructures of a recurrence network and the topology of the modeled system. Usually it is assumed that the future behavior of these processes does not depend on past behavior, but only on their current state. That might not be justified for many cases in question, e.g., there is no evidence that the occurrence of earthquakes was unrelated to former events and observation rather suggests the opposite.

In this context, processes with memory and memory-coupled networks were not yet thoroughly explored. Abandoning the above assumption, Time Series Analysis tools need to be adapted for analyzing non-reversible processes. Consequently, it would be obvious to ask for the interpretation of clusters and other network substructures with regard to the original processes.

### Tobias Willenbockel

**Education**

Diploma in Mathematics (2011)at Freie Universität Berlin. Diploma Thesis Title: 'Clusteranalyse in Netzwerken – Am Beispiel des Variational Bayesian Expectation Maximization Algorithmus'.

**Current project with GeoSim (since 01.10.11)**

‘Modelling of Seismic Activity via Network and Time Series Analysis’ at Freie Universität Berlin, Department of Mathematics and Computer Science, Institute of Mathematics.

Supervisors: Christof Schütte (FU Mathematics) and Frank Scherbaum (UP Geophysics).

The aim of my work is to achieve a better understanding of the dynamics of seismic activity by using a scalefree modelation of earthquakes via a network approach. For capturing the dynamics of seismic activity in such a network, it has to be coarse grained and analyzed mathematically for introducing, in a second step, fitting methods from time series analysis.

With this approach, a mathematical model which will allow probability based short term predictions of seismic activity is to be developed.

**1st author publications**

Willenbockel, Christian Tobias, and Christof Schütte. A variational bayesian algorithm for clustering of large and complex networks. Tech. Rep. 15-25, ZIB, (2015).

Willenbockel, Christian Tobias, and Christof Schütte. "Variational Bayesian Inference and Model Selection for the Stochastic Block Model with Irrelevant Vertices." (2016).

## RA II, Solid Earth

### Jorge Bernales

**Education**

M.Sc. in Geophysics (2013), University of Concepción, Chile. Thesis title: 'De-aliasing of short-term non-tidal atmospheric and oceanic mass variations for GRACE data processing'.

**Current project with GeoSim (since 15.10.2013)**

'Interactions between ice dynamics in Antarctica and regional sea level' at Section 1.3, Earth System Modelling, GFZ.

Supervisors: Maik Thomas (GFZ 1.3), Rupert Klein (FU Berlin) and Irina Rogozhina (GFZ 1.3).

The project aims to assess the complexity of the interaction between ice mass variation in Antarctica due to ice melt and ice calving processes, and variation in regional sea level due to both solid-earth response and global sea level change, providing a quantification of these processes. This requires a self-consistent treatment of short- and long-term dynamic responses of the Antarctic ice sheet to regional variations in climate and ocean, and long-term processes associated with glacial isostatic adjustment, both of which exert a strong influence on the ongoing local changes in sea level. Such approach will also lead to a better understanding of the impacts of the past and present changes in global and regional sea level on the dynamics of the Antarctic ice sheet, which have not been fully understood until now. The goal of this study shall be achieved by a complementary use of a coupled model of the climate-driven ice sheet and a viscoelastic lithosphere-mantle system together with a wide range of observations, in-situ measurements and palaeo-reconstructions.

**1st author publications**

Bernales J, Rogozhina I, Greve R, and Thomas M (2017) Comparison of hybrid schemes for the combination of Shallow Approximations in numerical simulations of the Antarctic Ice Sheet. The Cryosphere, 11, 247-265, doi:10.5194/tc-11-247-2017

## RA II, Atmosphere-Hydrosphere

### Annette Müller

**Education**

Diplom in Mathematics (2011) at TU Berlin. Thesis title: 'Das konforme Modul eines Knotens am Beispiel des symmetrischen Kleeblattknoten'.

**Current project with GeoSim (since 01.04.2012)**

'A transition scenario from three to two-dimensional regimes of turbulence based on the energy-vorticity theory of fluid mechanics using an infinite cascade of helicity related constraints' at the Institute of Meteorology, FU Berlin.

Supervisors: Peter Nevir (FU Meteorology)and Sebastian Reich (UP Mathematics).

Especially from the meteorological point of view, the challenge is to combine the different 2D-and 3D-turbulence models. A tornado is an example of a meteorological event appearing in the 3D convective scale. Those events are characteristic for three-dimensional turbulence and can be modelled as vortex filaments. Two-dimensional turbulence theory contains larger-scale processes. For example low-pressure and high-pressure areas. These synoptic processes can be described by point vortices. The energy-vorticity theory will be applied to combine these different models.

**1st author publications**

Müller, A., and P. Névir. "A geometric application of Nambu mechanics: the motion of three point vortices in the plane." Journal of Physics A: Mathematical and Theoretical 47.10 (2014): 105201.

Müller, Annette et al. Applications of point vortex equilibria: blocking events and the stability of the polar vortex. Tellus A (2015), 67, 29184, dx.doi.org/10.3402/tellusa.v67.29184

### Ariane Papke

**Education**

M.Sc. in physics (2013) at the Georg-August-Universität Göttingen and Max Planck Institute of Dynamics and Self-Organization. Thesis title: 'On Self-Similarity of Turbulent Flows over Porous Media'.

**Current project****with GeoSim (since 01.05.2013)**

'Multi-scale Models and Asymptotics of Atmospheric Flows'.

Supervisors: Rupert Klein (FU Mathematics) and Peter Nevir (FU Meteorology).

The dynamics of atmospheric vortices play a great role in many environmental flow phenomena. We utilize matched asymptotic analysis to describe vortex motion and structure. In some events moisture is an important factor, i.e. for hurricanes and tropical storms, and to account for these we specifically include diabatic heating in our model. We find that the theory is consistent with established models as regards precession frequencies of tilted vortices. The theory also provides new insight into tilt-induced mechanisms of vortex amplification/attenuation.

**1st author publications**

A. Papke and I. Battiato (2013) A reduced complexity model for dynamic similarity in obstructed shear flows. *Geophysical Research Letters*, 40 (15). pp. 3888-3892.

A. Papke (2009) Mindestens 17 müssen es sein. *Junge Wissenschaft*, 84 . pp. 24-31.

2008

A. Papke (2008) Wie viele Zahlen müssen es sein? *Die Junge Wissenschaft*, 79 . pp. 46-51.

### Isabel Urrutia

**Education**

Geology specialization (2014) at University of Concepcion, Chile. Thesis title: ‘Mega-thrust seismic cycle at Isla Santa María from numerical modelling of crustal deformation before, during and after the Mw8.8 Maule 2010 earthquake’.

**Current project with GeoSim (since 01.04.2014)**

‘Linking deformation patterns at various spatiotemporal scales along the South-American subduction zone’.

Supervisors: Onno Oncken (GFZ 3.1) and Ralf Kornhuber (FU Mathematics).

I will compile published GPS displacements and use time-series of the IPOC database to characterize the inter-seismic deformation and construct a realistic 3D FE-Model of the South American subduction zone incorporating all the available geometrical and rheological information to estimate the locking degree and its variation along the margin using a single consistent model allowing direct comparison of result.

I will analyze deformation patterns of the force-arc, manifested in the geology and geomorphology in a millennial time scale. I must choose a segment(s) along South American subduction margin that is best suited to this study. Suitable segments should have sufficient geo-chronological data and geological features for geomorphological analysis, e.g. drainage basins, marine terraces, peninsulas, etc. I will compile existing gradients in uplift rates complemented with detailed study of morphometric indices of drainage basins to postulate gradients of uplift rates and to distinguish different seismotectonic segments.

By comparing results of two analysis I will estimate the main parameters controlling the expression of the short-term inter-seismic deformation in the differential terrace uplift and margin segmentation.

## RA II, Hydrological Flow

### Matthias Munz

**Education**

Geoecology (2011) at Potsdam University. Majors: Modelling in Geoecology und Hydrology. Thesis title: 'Sand box experiments to evaluate the influence of subsurface temperature probe installation on temperature based water flux calculation'.

**Current project with GeoSim (since 01.04.2011)**

'Coupled water and heat transport modelling at the surface water-groundwater interface - from a highly instrumented stream stretch to the entire stream' at the Research Group “Water and Matter Transport in Complex Landscapes”at Institute of Earth and Environmental Science, Potsdam University.

Supervisors: Sascha Oswald (UP Hydrology) and Ralf Kornhuber (FU Mathematics).

Surface waters (SFW) and groundwater (GW) are the interconnected parts of stream catchments. They are coupled by variable water, solute and heat exchange processes through streambed sediments affecting water discharges as well as water quality. The goal of this research project will be to highlight, analyse and quantify the spatial and temporal variability of SFW-GW fluxes and heat exchange along a lowland river reach of the Selke River. This will be a sound basis for investigating quantitatively variations of sediment properties, boundary conditions and streambed morphology and also for subsequent generalization of SFW-GW exchange on reach scale river stretches and beyond.

**1st author publications**

M. Munz, S. Krause, C. Tecklenburg, A. Binley (2011). Reducing monitoring gaps at the aquifer–river interface by modelling groundwater–surface water exchange flow patterns. Hydrological Processes. Published online: 12 May 2011. DOI: 10.1002/hyp.8080.

Munz, M., Oswald, S. E., & Schmidt, C. (2016). Analysis of riverbed temperatures to determine the geometry of subsurface water flow around in-stream geomorphological structures. Journal of Hydrology, 539, 74-87.

Munz, M., & Schmidt, C. (2017). Estimation of vertical water fluxes from temperature time series by the inverse numerical computer program FLUX‐BOT. Hydrological Processes.

### Weishi Wang

**Education**

Msc in Water Resource Engineering （2011） at Katholieke Universiteit Leuven, Belgium.Thesis title: 'The detention area and the concave green space study in the city of Turnhout, Belgium'.

**Current project with GeoSim (since 01.04.2014)**

'Surface water and shallow groundwater exchange modelling'.

Supervisors: Sascha Oswald (UP Hydrology)

My research is try to use some method to increase the modelling accuracy and have a better understanding about the surface water and shallow groundwater interaction.

### Ulrich Wilbrandt

**Education**

MSc in mathemathics / scientific computing (2011) at FU Berlin. Thesis title: 'A posteriori Optimierung von Parametern in stabilisierten Finite-Elemente-Methoden für Konvektions-Diffusions-Gleichungen'.

**Current project with GeoSim (since 01.10.2011)**

We study coupled Stokes and Darcy equations which for example model surface water / ground water interactions. We will particularly focus on implementation, analysis, inf-sup stable versus stabilized discretizations. Furthermore we will apply these methods to real world problems from geophysics. This includes simulations in three space dimensions and time dependencies. We hope to compare our results to existing commercial codes available.

Supervisors: Volker John (WIAS) and Sascha Oswald (UP Meteorology).

**1st author publications**

Wilbrandt, U., Bartsch, C., Ahmed, N., Alia, N., Anker, F., Blank, L., ... & Meesala, R. (2017). ParMooN-A modernized program package based on mapped finite elements. Computers & Mathematics with Applications.

## RA III, Solid Earth

### Annabel Händel

**Education**

Diploma in Geophysics (2012) at the Institute of Earth- and Environmental Sciences of the University of Potsdam. Thesis title:'Data driven selection and ranking of ground-motion prediction equations for subduction zones'.

**Current project with GeoSim (since 01.04.2012)**

'Determination of attenuation properties from ambient vibrations' at the Institute of Earth- and Environmental Sciences, University of Potsdam.

Supervisors: Matthias Ohrnberger (UP Geophysics & Seismology), Frank Scherbaum (UP Geophysics & Seismology), Volker John (WIAS).

Understanding how earthquake waves are attenuated in the ground is crucial for any seismic hazard analysis. Especially the high-frequency filtering effect of the uppermost layers (described by the parameter kappa) can have a considerably influence on the proper prediction of future ground motions and needs to be assessed.

The main goal of this reserch project is the evolution of a non-destructive method to determine attenuation from noise data. We will invesitgate how seismic interferometry can be used to extract amplitude and attenuation information from ambient vibrations. We will further simulate a homogeneous scattering medium using finite differences to validate the obtained results and to better understand the mechanisms of seismic wave attenuation in the ground.

**1st author publications**

Haendel, A., Specht, S., Kuehn, N. M., and Scherbaum, F. (2015). Mixtures of ground-motion prediction equations as backbone models for a logic tree: an application to the subduction zone in Northern Chile. Bulletin of Earthquake Engineering, 13(2), 483-501.

Haendel, A., Ohrnberger, M., and Krüger, F. (2016). Extracting near-surface QL between 1-4 Hz from higher-order noise correlations in the Euroseistest area, Greece. Geophysical Journal International, 207(2), 655-666.

### Stefan Mauerberger

**Education**

Diploma in physics (2011) at Ludwig-Maximilians-Universität, Munich with a minor in Electronics and Geophysics. Thesis title: 'Investigation of Deep Earth Wave Propagation with the Spectral-Element Method in Spherical'.

**Current project with GeoSim (since 01.10.13)**

'Combining homogenization and Bayesian statistics by incorporating apriori information for downscaling results in full waveform inversion'.

Supervisor: Matthias Holschneider (UP Mathematics) and Serge Shapiro (FU Geophysics).

In my current project I investigate how to incorporate a-prioryinformation into the framework of full waveform inversion.

A-priory information can be taken from other disciplines, experiments or approaches.

As an example each, this might be limits for the elastic parameters from rock physicist, actual data given by a well-log or well known features obtained through high frequency approximations.

To introduce these information into the 'blurred' model obtained through full waveform inversion homogenization theory and Bayesian statistics are promising approaches.

### Anthony Osei Tutu

**Education**

MSc. Environmental and Geomatic Engineering (2013) at Politecnico Di Milano. Thesis title: 'Local gravity data (geoids) alignment using global models; satellite-only GOCE model and EGM2008'.

**Current Geosim Project (since 01.04.2014)**

'Linking global mantle dynamics with lithosphere dynamics using the geoid as a major constraint'.

Supervisors: Bernhard Steinberger (GFZ ), Irina Rogozhina (GFZ) and Volker John (WIAS).

The Earth's surface is broken into "tectonic plates" that move in different directions and at different rates.The interior (mantle), on which plates rest, also undergoes convection motion that in turn causes plate motion. Surface signatures of mantle convection can be observed as; plate motions with GPS permanent stations, dynamic geoid and topography, reflecting heterogeneity in the Earth's interior. The research seek to establish a link between surface observations (e.g., geoid, plate motion, stress field) and the evolution of the mantle, to resolve the uncertainties in the mantle and lithospheric structures using available observables, and to study the effect of complex rheology and structure of the lithosphere on the dynamic topography and geoid. This is to be achieved through coupling of a global mantle model with the model of lithosphere dynamics using the observed geoid as a major constraint and seismic data as a major input.

**Conference abstracts**

**A. Osei Tutu**, E. Rogozhin (2014), Strong paleoseismic manifestations in the south Baltic Sea basin, Kaliningrad city area, related to the retreat of the Fennoscandian Ice Sheet, *EGU 2014*, Vienna, Austria.

**A. Osei Tutu**, C. Gruber (2014), High resolution global gravity field modeling in spherical harmonics with regard to the constituents, *EGU 2014*, Vienna, Austria.

**A. Osei Tutu**, E. Rogozhin and B. Steinberger (2014), Linking global mantle dynamics with lithosphere dynamics - ILP LABPAX (2014), Hainburg, Austria.

## RA III, Atmosphere-Hydrosphere

### Forough Marzban

**Education**

MSc. in Computer Engineering -Artificial Intelligent- (2009) at Islamic Azad University Science and Research branch, Tehran, Iran. Thesis title: 'Identification and Predication of Chaotic time series by using Dynamic Neural Network Discrete time'.

**Project with GeoSim (will starts on 01.06.2014)**

'Estimation of high resolution 2m Temperature in Urban areas using Artificail intellegence methods: case study Berlin'

Supervisors: Sahar Sodoudi (FU Meteorology) and Lutz Prechelt (FU Computer Science).

It is necessary to develop a method for the estimation of air temperature with reasonable accuracy and spatial and temporal resolution in the urban areas with low temperature gauge density. For this reason, we should develop an appropriate machine learning techniques. Thus, in my research, first of all, different machine learning techniques including Neural networks (Dynamic Neural unit , Multilayer perceptrons (by using Back Propagation algorithm)), Bayesian Network, Fuzzy System, Support vector machine are considered and then, by applying each technique, a predicator model of air temperature will be generated. The comparison between these methods will be done, finally we evaluate the accuracy of each model and choose the best one for the high resolution temperature prediction.

### Edoardo Mazza

**Education**

B.Sc with Honours in 'Geophysics and Meteorology' (2013) at the University of Edinburgh. Thesis title: 'An investigation of the influence of different climate variability modes on the Atlantic tropical cyclone activity using a multiple linear regression model'.

**Current Project with GeoSim (since 1.10.2013)**

'Dynamic and thermodynamic control on medicane activity' at the Institute of Meteorology, FU Berlin.

Supervisors: Uwe Ulbrich (FU meteorology) and Rupert Klein (FU Mathematics).

The Mediterranean Sea, under specific circumstances, is an area prone to the development of intense sub-synoptic scale, axisymmetric cyclones, often referred to as “Medicanes”.

Although they share some visual and physical similarities with tropical cyclones, several aspects of their genesis and evolution remain unknown. My research is aimed at untangling the importance of different dynamical and thermodynamical factors throughout the lifecycle of medicanes using high- resolution numerical model simulations.The research may provide useful information to improve the forecasting of such cyclones and hence reduce the associated risk sin highly-vulnerable areas.

### Linda Michalk

**Education**

Diplom in mathematics (2011) at Freie Universität Berlin. Thesis title: 'Numerical methods for the linear advection equation: Plateaus vs. Extrema'.

**Current project with GeoSim: (since 01.10.2011)**

'Advanced finite volume schemes numerics for advection dominated problems' at the Institute of Mathematics, Department of Mathematics and Computer Sciences, Freie Universtät Berlin.

Supervisors: Rupert Klein (FU Mathematics) and Uwe Ulbrich (FU Meteorology).

The goal of my work is to compare existing numerical methods, find improvements or develope new ones, that yield satisfying results for solving geophysical problems - in particular advection dominated problems.

### Tobias Spiegl

Education:

MSc Applied Physical Geography (2013) - Julius-Maximilians-Universität, Würzburg. Thesis title: 'Potential Triggers for a Neoproterozoic Snowball Earth: Sensitivity Experiments with Planet Simualtor'.

**Current project with GeoSim (since 01.04.2013)**

'Solar Cycle Effects on Climate and their Modulation by decreasing Solar Activity and Climate Change (SOMOSA)'.

Supervisors: Ulrike Langematz (FU Meteorology), Rupert Klein (FU Mathematics).

To separate and quantify the effects of natural variability and anthropogenic influences on Earth's climate is one of the main targets in climate science today. In the course of that knowledge about solar imprints (in particular the 11-year cycle) needs to be improved. Since the middle atmosphere is highly sensitive to changes in total solar irradiance and spectral variations, we will use EMAC-MPIOM, a high-top climate-chemistry model with coupled ocean, to study the UV effect in the stratosphere as well as the role of energy consumption within the oceans.

We will examine the consequences of a linear decrease in the 11-year cycle, assuming a future Maunder-Minimum like grand solar minum till 2100, on stratospheric and tropospheric processes. We will also focus on coupling mechanisms between the middle and lower atmosphere, and variabilities of the North Atlantic and Arctic Oscillation.

**Publications**

Spiegl, T. C., Paeth, H., & Frimmel, H. E. (2015). Evaluating key parameters for the initiation of a Neoproterozoic Snowball Earth with a single Earth System Model of intermediate complexity. Earth and Planetary Science Letters, 415, 100-110.

**Conference abstracts**

**Spiegl** and Langematz (2015), Evaluating the Impact of different Maunder Minimum Reconstructions on Surface and Middle Atmosphere Climate with a state-of-the-art Chemistry-Climate Model, *Conference on Sun-Climate Connections, *Kiel, Germany.

**Spiegl** and Langematz (2015), Effect of the chosen solar irradiance dataset on simulations of a Future Grand Minimum: Results from a state-of-the-art Chemistry-Climate Model, *AGU Fall Meeting*, San Francisco, USA.

**Spiegl** and Langematz (2016), Potential impacts of a future Grand Solar Minimum on decadal regional climate change and interannual hemispherical climate variability, *EGU General Assembly*, Vienna, Austria.

## RA III, Hydrological Flow

### Tobias Pilz

**Education**

MSc in geoecology (2014) at University of Potsdam. Thesis title: 'Influence of climate change and management on water availability and erosion in a meso-scale catchment in South Africa'.

**Current project within GeoSim (since 01.03.2014)**

'Hydrological modelling at the management scale -- improving simulation results by data assimilation'.

Supervisors: Axel Bronstert (UP Hydrology) and Sebastian Reich (UP Mathematics).

Hydrological extremes such as droughts and floods have the potential to cause heavy damages on human goods and even threat their lives. Therefore, forecasting of such extremes with adequate lead-time is important to warn people and reduce damages. However, due to highly non-linear interactions hydrological simulations and forecastings are still accompanied by a high level of uncertainty. Quantifying and reducing that uncertainty is the main focus of my dissertation. To achieve this data assimilation techniques - widely used in meteorology but yet poorly recognised for hydrological applications - shall be applied and tested to make use of available observations covering different scales (including in-situ meaurements and remote-sensed data) and improve forecasting of droughts and floods.