Master theses

The moisture origin of extreme event "Hans"

Atmospheric moisture transport is a major factor in extreme floods. In this thesis project, you will use different numerical methods to identify the sources which provided the large amounts of water that lead to the flood caused by storm event "Hans". Moisture source calculations from backward trajectory analysis will be compared to a set up with moisture source diagnostics. The event-based results will be placed into the context of a climatological study. While identifying the factors that made "Hans" so extreme, it is also expected to quantify the probability with which such an extreme event can happen.

Relevant literature: The moisture source diagnostic of Sodemann et al. (2008). Application of the moisture source perspective to Central Europe (Sodemann and Zubler, 2010). Moisture sources for Atmospheric Rivers (Sodemann and Stohl., 2013)

Contact: Harald Sodemann (Numerical Modeling, Atmospheric Water Cycle)

Moisture source variability during periods of low predictability

The aim of this thesis is to investigate what role moist processes play during periods of low predictability. A moisture source identification is applied to data from the ECMWF 51-member ensemble to examine the variability of moisture sources and transport in each member. A keen interest in learing and applying ensemble methods as well as advanced atmospheric diagnostics based on backward trajectories are needed for this project.

Relevant literature: The moisture source diagnostic of Sodemann et al. (2008). Application of the moisture source perspective to Central Europe (Sodemann and Zubler, 2010). Measuring uncertainty in the ECMWF ensemble prediction system (Buizza et al, 1999). 

Contact: Harald Sodemann (Numerical Modeling, Atmospheric Water Cycle)

Drying of airmasses during the passage over the Norwegian coastal mountain range

The steep orography along the west coast of Norway is a key contributor to the annual rainfall total. Microphysical processes are triggered by the orographic lifting that ultimately remove water vapour during the passage of airmasses. This thesis aims to explore relation of changes in total column water to the efficiency of cloud processes in high-resolution model simulations and observations. In particular, one will explore the hypothesis that the total condensation in an airmass is reflected in gradients of the water vapour isotope composition across the mountain range. Measurements of total column water from GPS stations (in collaboration with Kartverket) will be compared to operational forecasts from MEPS and AROME Arctic, and water vapour isotope measurements from the SNOWPACE and ISLAS projects.

Relevant literature: The AROME forecast model (Seity et al., 2011).

Contact: Harald Sodemann (Numerical Modeling, Atmospheric Water Cycle)

Evaporation "hot spots" and the Deuterium excess signature in high-resolution climate models

The atmospheric water cycle is a key component of weather forecasting and climate models. This work is about identifying the regions where strong latent heat flux, or evaporation occurs, and how this affects the Deuterium excess, a stable isotope indicator of evaporation conditions. We have 6-hourly data from several current climate models which allow to compare how the evaporation process is simulated in each of them. A possible outcome of the work is to better understand where uncertainties in the water cycle of models are located, and how we can use additional measurements to improve them.

Relevant literature: Deuterium excess in the global water cycle (Pfahl and Sodemann, 2014). The NorESM climate model's water cycle (Bentsen et al., 2012).

Contact: Harald Sodemann (Numerical Modeling, Atmospheric Water Cycle)

Re-Analysis of data from Controlled Meteorological Balloons in Antarctica

Controlled Meteorological (CMET) Balloons (Voss et al., 2013) have been applied in several experiments in Antarctica since the first balloons were launched from the Troll station in Dronning Maud Land in 2012 (Stenmark et al., 2014). The balloons are used to sample basic meteorological parameters such as air temperature, humidity and wind speed and direction. They typically sample an order of magnitude more data than standard weather balloons. In most cases, the balloons have been controlled remotely from the USA and Norway via the Iridium system. In November 2017, boundary layer observations were made over the Ross Sea and compared with Antarctic Mesoscale prediction System (AMPS) forecasts (Dale et al., 2020). This flight performed 31 repeated soundings of the atmospheric boundary layer over a period of 70 hr. During the flight the balloon made close passes of the open Terra Nova Bay and Ross Sea polynyas. Since 2013, several CMET balloons have also been launched by the crew at the Finnish Aboa station. In January 2017, a balloon performed a trans-Antarctic flight from the Weddell to the Ross Sea and was airborne for 157 hours. In another experiment, two balloons were airborne for 60 and 106 hours with trajectory lengths of 885.8 km and 2367.4 km, respectively (Hole et al., 2016). The balloons carried out multiple controlled soundings from the surface up to 3.3 km. The most interesting feature detected by the CMET balloons was a mesoscale anticyclone over the Weddell Sea and the coastal zone, which was reproduced by the WRF model with reduced intensity. WRF results generally agreed with the observations. The results suggested here that CMET balloons could be an interesting supplement to Antarctic atmospheric observations, particularly in the free troposphere. The data from the balloons will be compared primarily with the Antarctic Mesoscale Modelling System (AMPS) model archive and ERA5. Interesting phenomena can be studied in detail for example using the WRF model. Exchange visits to the US or NZ can be arranged. 

Relevant literature:

Stenmark, A., Hole, L. R., Voss, P., Reuder, J., & Jonassen, M. O. (2014). The influence of nunataks on atmospheric boundary layer convection during summer in Dronning Maud Land, Antarctica. Journal of Geophysical Research: Atmospheres, 119(11), 6537-6548.

Voss, P. B., Hole, L. R., Helbling, E. F., & Roberts, T. J. (2013). Continuous in-situ soundings in the Arctic boundary layer: A new atmospheric measurement technique using controlled meteorological balloons. Journal of Intelligent & Robotic Systems, 70(1), 609-617.

Dale, E. R., Katurji, M., McDonald, A. J., Voss, P., Rack, W., & Seto, D. (2020). A Comparison of AMPS Forecasts Near the Ross Sea Polynya With Controlled Meteorological Balloon Observations. Journal of Geophysical Research: Atmospheres, 125(20). https://doi.org/10.1029/2019jd030591

Hole, L. R., Bello, A. P., Roberts, T. J., Voss, P. B., & Vihma, T. (2016). Measurements by controlled meteorological balloons in coastal areas of Antarctica. Antarctic Science, 28(5), 387-394.

Contact and Supervision: Lars R. Hole (Norwegian Meteorological Institute), Paul B. Voss (Smith College, MA, USA), and Harald Sodemann

Validation of remotely sensed wind profiles against radiosoundings

The marine atmospheric boundary layer is in the altitudes relevant for state-of-the-art and future expected wind turbines (0-300 m) not yet well understood. To improve our understanding of the complex interaction between wind shear, atmospheric stability and turbulence characteristics offshore, the offshore measurement campaign OBLEX-F1 (Offshore Boundary Layer Experiment at FINO1) has been initiated. It is an intensive observational campaign within the German Bight and is carried out by NORCOWE and several international partner institutions. The data from the experiment allows for an intensive and detailed study of the marine atmospheric boundary layer under various synoptic conditions.
Within this master project, wind profiles from a scanning lidar system (Leosphere WindCube 100S) should be validated against radiosoundings from two sites in the vicinity, Schleswig and Norderney. It will include a  statistical analysis of the observed differences as function of the synoptic situation, in particular wind speed, wind direction, and atmospheric stability.
More information on the project can be found here.

Contact: Joachim Reuder (Boundary layer meteorology, Energy meteorology)

The importance of longwave radiation flux divergence on stable boundary layer development

Radiation divergence is often assumed negligible in investigations of the atmospheric boundary layer. While this assumption might be applicable for many typical conditions, e.g. convective or near-neutral boundary layers, it might be often violated in the case of the stable boundary layer (SBL). Based on radiation measurements at two levels (1 m and 7 m) and eddy covariance measurements at 3 levels of a 10 m mast during a field campaign in February 2018 (Hailuoto, Finland) as part of the ISOBAR project (https://isobar2018campaign.w.uib.no/) the proposed master thesis will investigate the effect of radiative flux divergence close to the ground on turbulence and thus on structure and dynamics of the SBL.   

Advisors: Joachim Reuder, Stephan Kral

What are the Atmospheric Ingredients for large-scale Sea-Ice Break-Up Events?

Extratropical cyclones moving from the mid-latitudes into the Arctic Ocean sometimes have a devastating effect on the sea-ice cover. They bring warm and moist air masses into the Central Arctic and are typically associated with strong winds that can fracture the ice-cover over large regions. Although these events typically only last a few days, they likely play a climatological role. It is known that intense cyclones receive an important amount of their energy from diabatic processes, such as latent heat release during cloud and rain formation. For arctic cyclones the importance of this process is still unknown but might be of particular relevance as fractures in sea-ice expose the comparatively warm Arctic Ocean to the atmosphere, leading to extreme heat fluxes that can fuel the cyclone. This Master thesis project will look at the importance of these diabatic effects for a cyclone leading to a large-scale sea-ice break-up using a mesoscale atmospheric model and sea-ice boundary conditions from a state-of-the art sea-ice model, which is developed locally in Bergen at the Nansen Environmental and Remote Sensing Center. By systematically varying the initial humidity as well as heat fluxes, this Master’s project will find the importance of both the local fluxes as well as the transported moisture in the evolution of the cyclone and its feedback on the sea-ice break-up.

Advisors: Thomas Spengler (Atmospheric Dynamics) and Clemens Spensberger

Characteristics of Extreme Storms impacting Norway

The most intense cyclones hitting Norway during winter in the period 1979-2017 will be identified using a cyclone track database as well as land-based wind and precipitation observations. The tracks of the cyclones will then be used to assess what kind of development these cyclones underwent during their genesis and intensification, pinpointing the pertinent and most dominant processes contributing to the cyclone intensity. Particular focus will be on the role the jet stream as well as the sea surface temperature along the path of the cyclone, as well as the contribution of moist diabatic processes and surface fluxes. The overall goal is to identify possible development pathways and conducive conditions for these extreme cyclones to occur. Additional focus will be on the interannual variability of these storms and its association with large-scale weather patterns such as the North Atlantic Oscillation. The results will help us understand the necessary ingredients for extreme cyclone development affecting Norway in the current climate. Depending on the findings, it might be possible to make inferences about the future occurrence of these extreme storms in the vicinity of Norway.

Advisors: Thomas Spengler (Atmospheric Dynamics) and Clemens Spensberger

Response of Extratropical Cyclones to an Environment in a Changed Climate

Recent studies investigated the development of extratropical cyclones, where the authors varied environmental variables, such as temperature, stratification and humidity. The motivation for these sensitivity experiments is to improve our understanding of the development of extratropical cyclones in a future climate, where we know that the temperature, stratification and humidity will be altered. Several of these studies, however, had some pitfalls in their experimental setup. Here, we propose idealized simulations with a model tool developed at GFI, where we will study the response of differently initialized extratropical cyclones to variations in the aforementioned environmental parameters. Particular focus will be on understanding the role of latent heat release on the dynamic and thermodynamic development and nature of these cyclones. Special focus will on the response with respect to cyclones of different size, as cyclones are expected differently to changes in their environment dependent on their size. The study will lead to a better understanding of how mid-latitude cyclones might respond to a changing environment associated with climate change.

Advisors: Thomas Spengler (Atmospheric Dynamics)

Influence of Sea Surface Temperature on Storm Tracks

The effect of the sea surface temperature (SST), in particular SST fronts along the midlatitude western boundary current, on storm tracks is a matter on ongoing debate. Climatologically, storm tracks are collocated with the SST fronts in the western Atlantic and western Pacific and genesis of strong storms often occurs along these SST fronts. However, it is still unclear if the strength of the SST front or the absolute value of the SST itself has the primary influence on the strength and development of extratropical cyclones. Here, we propose to address this controversy using three different runs with a climate model: one control simulation, and two simulations where the SST front over respectively the Gulf Stream region and the Kuroshio region has been smoothed. Preliminary results using the smoothed Gulf Stream simulation show that the baroclinicity is increased (decreased) at location where the SST gradient is increased (decreased). These findings will be supported by data from idealised cyclone development simulations with different configurations for both the strength SST front and the absolute value of the SST. Different measures of baroclinicity will be compared with storm intensity and storm track measures for both the climate and idealized simulations.

Advisors: Thomas Spengler (Atmospheric Dynamics)

Sensitivity of Midlatitude Cyclone Development to Future Climate Environments

Our current understanding of how midlatitude cyclones and their intensity will change in a future climate remains limited. Parameters like static stability, tropopause height, and horizontal temperature gradients will all be affected by climate change. In this master project, we will use a conceptual model where the aforementioned parameters can be modified to represent future changes in climate. From different model runs, we will test how the growth rate, the horizontal scale, and the structure of midlatitude cyclones will change. The model is modified from the classical Eady model and is highly idealised, making it easier to understand the response to modified parameters. Focus will be on understanding the concept of the impacts from a changing climate, rather than representing the future climates in a complex and more realistic model.

Advisors: Thomas Spengler (Atmospheric Dynamics) and Kristine Flacké Haualand (PhD student)

Limits of Predictability of Extratropical Cyclone Development associated with the Structure of the Tropopause

Several recent studies on the predictability of extratropical cyclone development point to the sensitivity of the forecasts to the accurate representation of the tropopause. In particular, the sharpness of the vertical shear and stratification is often underestimated in operational weather forecasting models due to vertical model resolution or poor initial conditions based on insufficient observations to constrain the analysis. While it has been pointed out that there is an effect of this misrepresentation of the tropopause, it has not been sufficiently quantified how large the effect of certain deficiencies in representation of the wind or vertical stratification really is. In this Master thesis, we will use an idealized model based on the Eady problem, where we can modify the stratification and vertical wind shear to mimic different structures of the tropopause. The goal is to assess sensitivities of extratropical cyclone growth with respect to varying wind shear and stratification in the tropopause region. Results from this study will indicate how sensitive forecasts might be given certain deficiencies in the representation of the tropopause and thereby indicate associated predictability issues.

Advisors: Thomas Spengler (Atmospheric Dynamics) and Kristine Flacké Haualand (PhD student)

Role of Cold Air Outbreaks in Atmosphere-Ocean-Ice Interactions in a coupled mixed layer Model

Cold air outbreaks play a crucial role in the air-sea heat exchange in the higher latitudes. However, we still lack some basic understanding about the sensitivities of these phenomena to latent heating and the role of coupling to the ocean. To further explore these sensitivities, we coupled a moist convective atmospheric boundary layer model with an ocean mixed layer model to investigate the response of moist convection as well as ocean mixing during cold air outbreaks. The model yields a two-dimensional steady state for a cold air outbreak downstream of an ice edge. The atmospheric model is based on the equations for liquid water potential temperature and total water mixing ratio, the oceanic model on those for temperature and salinity.

Using this model, a variety of coupled and uncoupled solutions with different resolutions and sea ice concentrations can be assessed. Varying sea ice concentration and resolution alters the distribution and intensity of the air-sea heat exchange with ramifications for mixed layer depths in both the atmosphere and ocean. The obtained results will have implications for numerical weather prediction and climate models, in particular regarding model resolution and the degree of coupling for the representation of air-sea interaction during cold air outbreaks. Furthermore, the model can be used to assess the hydrological cycle in cold air outbreaks, yielding important insights into the role of evaporation and precipitation in cold air outbreaks.

Advisors: Thomas Spengler (Atmospheric Dynamics) and Clemens Spensberger (Researcher)

Atmospheric convection - building a model for vertical motion using observations and theory

Atmospheric convection is ubiquitous in the atmosphere, yet we still struggle to understand certain aspects of it. Convection leads to overturnig in the atmosphere and vertical transport and can initiate clouds and severe precipitation. In this study, we will develop and extend a theoretical model to predict the vertical motion in convection. The model has several free parameters and needs to be provided with an environmental profile of atmospheric conditions.

The topic of the thesis will explore the parameter space of the model and at the same time use observations obtained from motor and glider airplaines equipped with a recently in-house developed measuring device. The overall goal is to predict the vertical motion obsered in convection, as experienced by gliders flying through the atmosphere. The model will thereby yield a more detailed insight into the workings of convection and at the same time might lead to an improved understanding that could contribute to new parameterisations of convection and convective transport.

Advisors: Thomas Spengler (Atmospheric Dynamics)

Modeling the energy balance of the snowpack in the non-melt zone of the Greenland Ice Sheet.

The objective of this research project is to close the energy budget for the snow pack and be able to simulate the snow temperatures of the Greenland Ice Sheet. This is important for our ability to predict when melting occurs on the ice sheet and hence our ability to accurately simulate the mass balance of the Greenland Ice Sheet. More information can be found here https://steenlarsen.w.uib.no/student_opportunities/ or in the pdf-file. This project is related to field work in Greenland.

Advisors: Hans Christian Steen-Larsen and Joachim Reuder

Measuring the mass balance in the interior of the Greenland Ice Sheet.

The objective of this research project is to quantify the mass balance of the interior of the Greenland Ice Sheet where a sublimation and condensation plays significant roles. Through a combination of snow height measurements, gradient measurements, and multiple Eddy-Covariance measurements, the project will determine the magnitude and uncertainties of the different components of the mass balance. For our ability to simulate the mass balance of the Greenland Ice Sheet and its contribution to sea level rise it is important to know the relative uncertainties of the mass balance components. More information here https://steenlarsen.w.uib.no/student_opportunities/. This project is related to field work in Greenland.

Advisors: Hans Christian Steen-Larsen and Joachim Reuder

Understanding the physical processes governing the formation of precipitation.

This research project focuses on understanding the processes involved in moisture uptake and storage in the atmosphere. Using water stable isotopes the objective is to understand the physical processes between atmospheric water vapor and precipitation. We have at Bermuda the longest calibrated record of continuous atmospheric water vapor isotopes and daily precipitation isotope measurements giving us a unique opportunity to combine theoretical calculations and model simulations with observations. More information here https://steenlarsen.w.uib.no/student_opportunities/. This project is related to field work in Bermuda.

Advisor: Hans Christian Steen-Larsen

Quantifying how the climate is recorded in the ice core water isotope signal.

This research project is closely linked with the funded European Research Council project SNOWISO and H2020 project  BEOI and is focused on understanding the climatic drivers of the water isotope signal in the snow, which falls on top of the Greenland and Antarctic Ice Sheet. Through a combination of moisture tracking, climate models, and direct observations of the water isotopic composition of the precipitation and the surface snow the aim is to improve our ability to understand the paleoclimate record from the ice cores by understanding the climate fingerprint in the water isotopes. More information here https://steenlarsen.w.uib.no/student_opportunities/. This project is related to field work in Greenland.

Advisors: Hans Christian Steen-Larsen and Anne-Katrine Faber

Understanding the drivers of the hydrological cycle over the Tibetan Plateau.

The ‘third pole’ is the planet’s largest reservoir of ice and snow after the Arctic and Antarctic. Meltwater feeds ten great rivers, including the Indus, Brahmaputra, Ganges, Yellow and Yangtze, on which almost one-fifth of the world’s population depends. However, we still lack a quantitative understanding of the role of each process in the overall water budget. The research project focuses on obtaining a better understanding of the relationships between the third pole’s complex terrain and the weather patterns and processes that affect precipitation and ice-melting. As models struggle to reproduce the climate over the third pole the overall objective is improve the models to guide regional strategies for adapting to climate change, for preserving and restoring ecosystems and conserving biodiversity. More information here https://steenlarsen.w.uib.no/student_opportunities/ . This project is in collaboration with Institute of Tibetan Plateau Research and China’s Pan-TPE research program and is related to field work in Tibet.

Advisor: Hans Christian Steen-Larsen

Wind estimation by unmanned aircraft system measurements and machine learning models

The GFI research group on Boundary layer and wind energy​ meteorology lead by Joachim Reuder links research with boundary layer meteorology and unmanned aircraft systems (UAS). The subjects range from boundary layer meteorology, orographic effects to solar UV radiation. As a part of an R&D project we are offering a master's thesis.

The Innovative Strategies for Observations in the Arctic Atmospheric Boundary Layer Program (ISOBAR) is a research project investigating stable atmospheric boundary layer (SBL) processes, whose representation still poses significant challenges in state-of-the-art numerical weather prediction (NWP) models. In ISOBAR ground-based flux and profile observations are combined with boundary layer remote sensing methods and the extensive usage of different unmanned aircraft systems (UAS). During February 2017 and 2018 we carried out two major field campaigns over the sea ice of the northern Baltic Sea, close to the Finnish island of Hailuoto at 65°N.

The motivation of the Master Thesis is to apply machine learning to predict the wind direction and wind speed based on the pitch, roll and yaw angles using drone data from the ISOBAR campaign. Wind observations from a 10-m mast, lidar and sodar profiles may serve as training and validation data. You will work in an innovative interdisciplinary project and make significant contributions to the advancement in drone measurements. During your thesis you will work in close collaboration with the scientific and technical staff on the following tasks:

• Literature study on machine learning.
• Evaluate the ISOBAR data.
• Construct a machine learning model
• Writing report and presentation.

The candidate should have programming experience. You are a good team player, communicative and highly motivated. You enjoy taking responsibility of tasks and executing them in an autonomous and careful manner.

If you have any questions, please don’t hesitate to contact Stephan Kral (stephan.kral@uib.no) or Pirmin Philipp Ebner (pirmin.ebner@uib.no). We will be happy to answer any questions or offer further information.

Experimental Analyses of Snow Metamorphism on the Stable Water Isotope Composition in Snow/Ice and Air

Since the 1960s, stable water isotopes in polar snow and ice have been used as proxies for both local and global temperature records. The interpretation of ice core data and the comparison with atmospheric model results implicitly rely on the assumption that the snowfall precipitation signal is perfectly preserved in the snow-ice matrix ignoring snow-vapor exchanges between surface snow and atmospheric water vapor. However, a recent study carried out on top of the Greenland Ice Sheet combining continuous atmospheric water vapor isotope observations with daily snow surface sampling documented a clear day-to-day variation of surface snow isotopic composition in-between precipitation events. This effect was interpreted as being caused by uptake of the synoptic driven atmospheric water vapor isotope signal by individual snow crystals undergoing snow metamorphism. However, the impact of this process on the isotope-temperature reconstruction is not yet sufficiently understood, but crucial, compared to interstitial diffusion, and will alter the isotope mean value.

In order to fully understand and interpret the ice core proxy it is important to understand the mechanisms possibly changing the snow signal even after deposition. Therefore, the goal of this Master Thesis is to analyse how post-depositional processes like snow sublimation and snow metamorphism can affect the isotopic composition of the snow which forms later the ice. In this thesis, an experimental study on the effect of snow metamorphism and snow sublimation on the snow isotopic composition in controlled laboratory conditions has to be done in the laboratory at GFI. You will work in an innovative interdisciplinary project and make significant contributions to the advancement of stable water isotope research in snow and ice. During your thesis you will work in close collaboration with the scientific and technical staff.

Advisors: Pirmin Philipp Ebner (pirmin.ebner@uib.no) and Hans Christian Steen-Larsen (hans.christian.steen-larsen@uib.no)

Modelling the impact of Snow Metamorphism on the Distribution of Stable Water Isotope in Snow/Ice.

Since the 1960s, stable water isotopes in polar snow and ice have been used as proxies for both local and global temperature records. The interpretation of ice core data and the comparison with atmospheric model results implicitly rely on the assumption that the snowfall precipitation signal is perfectly preserved in the snow-ice matrix ignoring snow-vapor exchanges between surface snow and atmospheric water vapor. However, the isotopic profile in ice cores, from which the climate signal is extracted, is subject to alterations induced by processes occurring right after snowflake deposition and until the complete compaction of snow grains into ice. In ice sheets, the effect of these so-called post-depositional processes is reflected mainly in the diffusion of isotopes along concentration gradients, created by the succession of layers with distinct isotopic composition. On the other hand, snow metamorphism, the process of grain coarsening that transforms snow to ice, also alters the isotopic composition in the ice matrix. Transport of water vapor molecules and continuous phase changes, the two mechanisms involved in metamorphism, impact isotopes on slightly different magnitudes. This modifies the abundance of isotopes in the coexisting phases. This phenomenon of partitioning of isotopes in the different coexisting phases, called fractionation, typically leads to the enrichment of heavier isotopes in ice.

A better assessment of diffusion and fractionation occurring during metamorphism is necessary to further leverage the data gained from ice core analysis. Therefore, this thesis seeks to fill this gap by refining the existing diffusion equation, that described the transport of heavy isotopes in firn, so that fractionation occurring during metamorphism also imprints its effect on simulated isotopic profiles. The goal of this Master Thesis is to set up a numerical model to analyze the impact of snow metamorphism on the distribution of stable water isotope in snow. You will work in an innovative interdisciplinary project and make significant contributions to the advancement of stable water isotope research in snow and ice. During your thesis you will work in close collaboration with the scientific and technical staff

Advisors: Pirmin Philipp Ebner (pirmin.ebner@uib.no) and Hans Christian Steen-Larsen (hans.christian.steen-larsen@uib.no)