Supervisor: Gustav Strandberg, SMHI (Gustav.Strandberg@smhi.se)

Rossby Centre, SMHI has produced a large data set of projections of climate change (until year 2100) in Scandinavia together with gridded observations for the recent past (1961-present). This data makes it possible to analyse different aspects of climate change. For example observed change compared to projected future change, or variability in climate. It is also possible to study the different parts of the model chain, such as the choice of global model, regional model or emissions scenario; or how bias adjustment affects simulated climate change. Another line of study could be to look at specific events such as heat waves, cold spells or extreme precipitation events.

This project is to a large extent about analysing large data amounts. It is required to have knowledge about Unix systems. It is also required with knowledge about bash, CDO, Python or the like, to be able to work with the data at the super computer at NSC.

Contact: Anna Helena Hultberg, Gale Force (annahelena.hultberg@galeforcesweden.com)

Gale Force AB, with office in Norrköping, was established 2020 with the main purpose to offer weather routing services within the global shipping industry.

Ocean currents have an noticeable impact to vessels performance and the strength of the current varies significantly in some areas.

In this project Gale Force would like to evaluate different ocean current models to see how accurate they are, how these could be combined to get the best out of it and how it affect the coastal areas.

Contact: Anna Helena Hultberg, Gale Force (annahelena.hultberg@galeforcesweden.com)

Gale Force AB, with office in Norrköping, was established 2020 with the main purpose to offer weather routing services within the global shipping industry.

Tidal areas are well known, but how should it be forecasted in the most optimal way and how do it affect the forecasts in the areas where their effect is strongest?

In this project Gale Force would like an in-depth analyse on the impact of tidewater and how it affect the forecast in these areas.

Contact: Anna Helena Hultberg, Gale Force (annahelena.hultberg@galeforcesweden.com)

Gale Force AB, with office in Norrköping, was established 2020 with the main purpose to offer weather routing services within the global shipping industry.

Global forecast models, such as ECMWF, are very good for the oceans. However, when getting in to coastal areas the global models can be less accurate and it is a probability that it could be beneficial to combine with use of regional forecast models.

In this project Gale Force would like to perform an evaluation of selected regional models against the global forecast model from the ECMWF.

Supervisor: Gunilla Svensson (gunilla@misu.su.se)

As part of the WWRP Polar Prediction Project, observational and model data are collected and organized in a database to facilitate model evolution with focus on processes within the YOPPsiteMIP framework. In this project, suitable diagnostics will be developed and applied to analyse biases or misrepresentation of processes relevant in Arctic conditions. More information can be found here: https://www.polarprediction.net/ and https://www.polarprediction.net/key-yopp-activities/yoppsitemip/

Supervisors: Léon Chafik (leon.chafik@misu.su.se) and Ezra Eisbrenner (ezra.eisbrenner@misu.su.se)

Wind forcing over the North Atlantic can cause regional and local sea level variations acting from months to decades. In this project, the student will use a new sea level dataset made specifically for the Baltic Sea to understand how atmospheric circulation patterns in the North Atlantic impact sea-level variability, following the approach used in Chafik et al. (2017). The student will focus on the monthly-to-interannual variability of sea level  (Chafik et al., 2019, Mangini et al. 2021; Dangendorf et al., 2021) and how it is tied to atmospheric circulation. A set of python routines exist already and will be used to construct the gridded sea level data. The student will in this project learn more about atmospheric circulations patterns and how they influence sea level and surface ocean circulation.

References

Chafik, L., Nilsen, J. E. Ø. and Dangendorf, S. 2021. Impact of North Atlantic teleconnection patterns on northern European sea level. JMSE. 5, 43, DOI:10.3390/jmse5030043. Article link here

Chafik, L., Nilsen, J.E.Ø., Dangendorf, S. et al. North Atlantic Ocean Circulation and Decadal Sea Level Change During the Altimetry Era. Sci Rep 9, 1041 (2019), DOI:10.1038/s41598-018-37603-6. Article link here

Mangini, F., Chafik, L., et al. 2021. The relationship between the eddy-driven jet stream and northern European sea level variability. Tellus A: Dynamic Meteorology and Oceanography. 73, 1886419, DOI:10.1080/16000870.2021.1886419. Article link here

Dangendorf, S., Frederikse, T., Chafik, L. et al. 2021. Data-driven reconstruction reveals large-scale ocean circulation control on coastal sea level. Nat. Clim. Chang. 11, 514–520, DOI:10.1038/s41558-021-01046-1. Article link here

Supervisors: Léon Chafik (leon.chafik@misu.su.se) and Ezra Eisbrenner (ezra.eisbrenner@misu.su.se)

Extreme warm events over the ocean or Marine heat waves (Hobday et al., 2016) have seen a tremendous increase in frequency over the past decades. These events can have devastating effects on the marine climate and ecosystems (Smale et al. 2019). The physical drivers of marine heat waves include changes in air-sea fluxes that coincide with specific atmospheric patterns or heat advection due to changes in the ocean circulation (Holbrook et al., 2019; Oliver et al. 2020). In this project, the student will use sea-surface temperature data to analyze the intensity, variability and trends of Marine heat waves at higher latitudes in the Nordic Seas and Arctic Ocean (a python package already exists). In extension, the student will make an attempt to understand the main processes behind the extreme marine heat waves in the region. The student will in this project learn more about extreme heat waves in the ocean, how to statistically analyze these events and their associated ocean-atmosphere coupling.

References:

Hobday, A. et al. 2019 A hierarchical approach to defining marine heatwaves. Progress in Oceanography, 141, 227–238, DOI:10.1016/j.pocean.2015.12.014. Article link here

Smale, D.A., Wernberg, T., Oliver, E.C.J. et al. Marine heatwaves threaten global biodiversity and the provision of ecosystem services. Nat. Clim. Chang. 9, 306–312 (2019), DOI:10.1038/s41558-019-0412-1. Article link here

Holbrook, N.J., Scannell, H.A., Sen Gupta, A. et al. A global assessment of marine heatwaves and their drivers. Nat Commun 10, 2624 (2019), DOI:10.1038/s41467-019-10206-z. Article link here

Oliver, E. C. J., Benthuysen, J. A., et al. 2021. Annual Review of Marine Science. 13:1, 313-342, DOI:10.1146/annurev-marine-032720-095144. Article link here

Supervisor: Inga Monika Koszalka (inga.koszalka@misu.su.se)

This project is about analysis of the Acoustic Doppler Current Profiler (ADCP) velocity data collected during several expeditions with R/V ELECTRA in the Baltic Proper/Western/Central Gotland Basin. We will analyze this data set as well as "synthetic" ADCP data extracted from an ocean model using structure functions and related diagnostics in order to quantify the dominant space and time scales of variability of the turbulent and wind-driven currents. We will also compare the results from ADCP data to those derived from spectral analysis of the model data and interpret them in terms of theoretical predictions. Depending on student interests and scope of the thesis (45p or 60p), the project can be expanded to include: analysis of decadal model output to quantify time variability on seasonal-to-interannual scales, assessment of impact of the wind forcing, or application of machine learning techniques to analysis of the ADCP data. Good programming skills (preferably Python, possibly MATLAB) and a burning interest in statistics and data analysis are a requirement.

The student will learn about the salient features of the Baltic Sea circulation, underpinnings of the ADCP measurement techniques, spectral theories for turbulent flows, structure functions and spectral analysis techniques as well as uncertainty measures.

The project will be conducted in collaboration with the Baltic Sea Centre.

Supervisors: John Prytherch (john.prytherch@misu.su.se), Michael Tjernström (michaelt@misu.su.se)

The Arctic is warming rapidly relative to the rest of the world, and an accurate description of the physical feedbacks responsible for this warming requires knowledge of the atmospheric structure in the Arctic.

In this project, the student will use temperature, humidity and wind profiles measured by weather balloon soundings and a (remotely sensing) microwave radiometer to determine the atmospheric structure in the Arctic during the recent Synoptic Arctic Survey 2021 (SAS2021) expedition to the central Arctic.

The student will use data collected during SAS2021 to study the vertical structure of the Arctic atmosphere to, for example, calculate mean profiles and distinguish periods that deviate much from that mean profile, diagnose inversions etc. Following the approach of Tjernström et al. (2019) they will also use the 6-hourly soundings to bias correct the higher-frequency radiometer data to estimate systematic and random deviations and finally generate a continuous description of the atmospheric structure. Code (MATLAB) to begin this approach is available. Some experience with coding (MATLAB, Python, or R etc) and data analysis would be helpful.

In this project the student will learn about:

• how the atmosphere’s vertical structure can be measure using different techniques, as well as corresponding errors and caveats
• Arctic meteorology and the vertical structure of the Arctic atmosphere
• how to generate useful temperature products from a complex dataset

Possible extensions to the project could be:

• How the vertical structure of the atmosphere affects the surface energy budget (also measured during SAS2021)
• The accuracy of numerical forecasts in the Arctic, by comparing soundings to ECMWF forecast profiles

References:

More information about the Synoptic Arctic Survey 2021

Tjernström, Michael, Matthew D. Shupe, Ian M. Brooks, Peggy Achtert, John Prytherch, and Joseph Sedlar. "Arctic Summer Airmass Transformation, Surface Inversions, and the Surface Energy Budget", Journal of Climate 32, 3 (2019): 769-789, DOI:10.1175/JCLI-D-18-0216.1, Article link here

Supervisors: Kathrin Finke (kathrin.finke@misu.su.se) and Abdel Hannachi (a.hannachi@misu.su.se)

The stratosphere is known for its large-scale dynamic variability during winter. So called sudden stratospheric warmings (SSWs) during which the stratospheric polar vortex is strongly disrupted may influence the troposphere and surface weather for up to two months after their initial signal in the stratosphere (Baldwin and Dunkerton 1999, 2001) and have thus been found to enhance midlatitude and extratropical predictability.

Among other ways, SSWs may be divided into reflecting and absorbing events, during which the stratosphere either reflects or absorbs upward propagating planetary waves (Kodera et al. 2015). Kodera et al. (2015) find the absorbing type to project onto the northern annular mode (NAM) whereas the reflecting type is associated with strong westerlies over the North Atlantic and blocking over the North Pacific sector.

The objective of this thesis is to identify, based on catalogued events, reflecting and absorbing SSWs in reanalysis data and analyse the differences of the two categories in terms of stratospheric evolution and their tropospheric impacts, e.g. surface climate.

References:

Baldwin, M. P., and T. J. Dunkerton (1999), Propagation of the Arctic oscillation from the stratosphere to the troposphere, J. Geophys. Res., 104, 30,937–30,946, DOI:10.1029/1999JD900445, Article link here

Baldwin, M. P., and T. J. Dunkerton (2001), Stratospheric harbingers of anomalous weather regimes, Science, 294, 581–584, DOI:10.1126/science.1063315, Article link here

Kodera, K., H. Mukougawa, P. Maury, M. Ueda, and C. Claud (2016), Absorbing and reflecting sudden stratospheric warming events and their relationship with tropospheric circulation, J. Geophys.Res. Atmos., 121,80–94, DOI:10.1002/2015JD023359, Article link here

Supervisors: Aiden Jönsson (aiden.jonsson@misu.su.se) and Frida Bender (frida.bender@misu.su.se)

Introduction:

Climate change is projected to increase the frequency of hydrometeorological extremes in the near future; these extremes can lead to natural disasters which can impact society in a number of ways, not the least of which being loss of life and livelihoods. Natural disasters also disproportionately impact developing countries, displace people and threaten peace. In order to enhance preparedness where natural disasters will most likely become more frequent with global warming and to ensure that the global community is prepared to allocate resources towards where they are needed most, detailed information about extreme weather in the future is needed.

Records of disasters such as the global Emergency events Database (EM-DAT) give historical information on the impacts as well as the when and where of natural disasters such as flooding and drought, but lack physical information about the magnitude of meteorological variables during the events. Recently, work on attaching geographic information to records of natural disasters made it possible to match meteorological variables from re-analysis with the events, and test them against resulting social and economic effects (Dellmuth et al., 2021). The geographic information has now been extended in order to include nearly 10,000 events in 40,000 locations between 1960 and 2018 (Rosvold and Buhaug, 2021), giving the opportunity to further investigate the why and how of natural disasters. This project aims to build off of the methods used in Dellmuth et al. (2021) and gain further insight into extreme weather and natural disasters, and how they impact society.

Project proposal:

The project’s scope and goals can be discussed and organized according to the length of the master’s degree project. The student should be skilled with statistical calculations and large data handling using e.g. Python.

The student will match the reported natural disasters in GDIS with re-analysis output for variables capable of capturing the meteorological conditions during the natural disaster (e.g. accumulated precipitation for flooding and drought events). These values will then be checked for being representative of extreme values in the entire climatological distribution of the variable in order to validate that the reported disasters can be connected to measurable meteorological conditions. This will be accomplished with a thorough comparison of statistical distributions and extreme value analysis.

A possible second moment of the project involves the application of these findings to future climate projections using simulations in the Coupled Model Intercomparison Project (CMIP). The student may begin to investigate the possibility of applying the findings of the first moment to study the evolution of extreme weather in a future climate. The distributions, extreme values and their properties retrieved in re-analysis will need to be compared against those in climate models. The end goal will be to use these distributions to model the frequency and magnitude of natural disasters in a future climate, and to compare these against other projections of natural disasters under global warming in the existing literature on the topic.

References:

Dellmuth, L. M., Bender,  F. A.-M., Jönsson A.R., Rosvold E. L., von Uexkull, N. Humanitarian need drives multilateral disaster aid. Proceedings of the National Academy of Sciences 118 (4) e2018293118 (2021), DOI:10.1073/pnas.2018293118. Article link here

Rosvold, E. L., Buhaug, H. GDIS, a global dataset of geocoded disaster locations. Sci Data 8, 61 (2021), DOI:10.1038/s41597-021-00846-6. Article link here

Supervisor: Johan Nilsson

The surface ocean salinity is closely correlated with the net evaporation (evaporation - precipitation): high (low) salinities are encountered where the net evaporation is positive (negative).

Global warming is expected to increase the hydrological cycle, but it is challenging to assess global changes in the hydrological cycle from observations over land. However, observed changes in surface salinity has been suggested to provide a more robust measure of long-term changes in the hydrological cycle. This has been tested and the method is known as the “ocean rain gauge”.  The idea is that the changes in ocean salinity are proportional to the changes in net evaporation.

This projects examines how accurate the assumption of a proportional between changes in net evaporation and surface salinity is. For this purpose observed salinity changes are analysed using some new ideas of how the data can be represented using probability distribution functions. A simple time-dependent diffusive model of the surface salinity will be used to examine if steady-state conditions can be used, which are assumed in the present ocean rain gauge method. The results can improve the ocean rain gauge method, and also reveal information on the processes which cause the surface salinity to be higher in the Atlantic than in the Pacific; a feature critical for the present-day deep-water formation in the North Atlantic. 

Literature:

Ocean Salinities Reveal Strong Global Water Cycle Intensification During 1950 to 2000

Is the surface salinity difference between the Atlantic and Indo–Pacific a signature of the Atlantic Meridional Overturning Circulation?