| dc.description.abstract | Cyclones are frequently found in the Arctic and can have wide-ranging impacts on the region. Nevertheless, few studies have focused on the development of cyclones originating in the Arctic, in contrast to the extensively studied midlatitude cyclones. Thus, in this thesis we study the genesis and development of cyclones originating in the Arctic. As these cyclones exhibit large variability in temperature and moisture content, we separate them into two groups - warm and moist cyclones versus cold and dry cyclones. This separation is based on the equivalent potential temperature θe, a quantity which is a function of temperature and humidity and is conserved for moist-adiabatic motion. The cyclones are tracked using the Melbourne tracking scheme on ERA5 reanalysis data, and we apply an isentropic framework to study the overturning circulation of the two groups. Cyclones in both groups show a thermally direct circulation, with higher θe (warm, moist) air rising and lower θe (cold, dry) air sinking. The high-θe cyclones have deeper but less vigorous overturning circulation compared to the low-θe cyclones. The circulations are most different at and just after cyclogenesis, and become more similar over time. Prior to cyclogenesis, the two groups show opposite atmospheric anomalies in the Arctic up to several days before the genesis event, suggesting that the environment is preconditioned. These atmospheric anomalies also exhibit a dipole pattern over the study region and North Atlantic, suggesting that the cyclones are related to large-scale systems such as jet and weather regimes. Further research on the connection between the two groups and the regimes is proposed. Different characteristics and genesis locations suggest that low-θe cyclones arise from baroclinicity from the sea ice edge while high-θe cyclones arise from other processes such as secondary genesis or orographic processes. Our results contribute to a better understanding of how thermodynamic characteristics of cyclones are connected to cyclone development and impacts on the Arctic region. Cyclones affect the local weather and can result in extreme warming, storm surges and flooding. Hence, knowing more about the development and impacts of cyclones can give more insight into how extreme cyclone events evolve. | |
