Non-stationarity of teleconnections in the climate system

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6During my PhD. I will be researching teleconnections and their non-stationarity in our climate system. The connections of different climate modes like the El Nino Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), or the North Atlantic Oscillation (NAO) to each other and to other processes are large areas of active research (e.g. Rodriguez-Fonseca et al., 2016). These teleconnections are of high importance as the interaction between climate modes can directly change the local climate of large regions (e.g. Europe for changes in the NAO). In addition the existence of teleconnections between tropics and extra tropics can have large impacts on our ability to forecast the extratropical climate as O'Reilly (2018) has shown. O'Reilly et al. (2019) have shown that these teleconnection changed in the past and will also very likely change in the future in a warming world again. The changes and non-stationarities of teleconnections are also highly influenced by small changes in internal atmospheric dynamics and there is still large uncertainties why these teleconnections changed in the past. Therefore it is of high importance to investigate these changes in the past to understand how teleconnections will change in the future. As a first test case, the extremely warm and well predictable winter in northern Europe of 2019/2020 will be investigated. The anomalous winter was driven by a positive NAO. This positive NAO likely had some unusual teleconnection patterns active. Identifying the teleconnection pattern of this winter is therefore a useful first step in understanding why teleconnections can differ from year to year.