Master Thesis defense by Simon Peter Heselschwerdt

Title: "An analysis of the consistency between observed atmospheric winter variability and weather anomalies in the North Atlantic region"

Abstract: The complex spatial and temporal evolution of large-scale atmospheric circulation in the North Atlantic region is simplified by modes of climate variability. Those modes of variability present a pronounced teleconnection with weather conditions in the area, posing a high significance for resent climate science. Hence, this thesis aims to analyze the relationship between observed atmospheric winter climate variability and temperature and precipitation anomalies. Therefore, an empirical orthogonal function analysis of mean sea level pressure in the North Atlantic region for the period 1950-2021 has been conducted. In doing so, the ERA5 reanalysis dataset has been used to analyze atmospheric modes of variability during the extended boreal winter season (NDJFM).
Additionally, a principal component regression analysis has been performed to examine the importance of the different climatic modes on weather conditions, with a particular focus on more extreme anomalous winter conditions.
The empirical evidence in this dissertation confirms a strong influence of the climatic modes on the weather conditions in the North Atlantic domain. Although the NAO is generally identified as the governing variability mode, the findings of this paper outline an unexpected asymmetry of the NAO pattern with respect to the temperature segregated analyses.
Besides, this study demonstrates characteristic teleconnection patterns of the four leading variability modes. The stated findings may be considered a promising aspect of reconstruction approaches, particularly in the scope of the GreenPlanning project.

Keywords: ERA5 reanalysis, atmospheric modes of variability, NAO, climate variability, NAO reconstructions, empirical orthogonal function analysis, principal component regression analysis, GreenPlanning project