Datensatz

Zusammenfassung

Despite the potentially severe impact of atmospheric blocks on surface weather, the correct prediction of blocking lifecycles remains a key challenge in current numerical weather prediction models. Increasing evidence suggests that latent heat release in cyclones, the advection of cold air from the Arctic over the North Atlantic, and associated air-sea interactions over the Gulf Stream are key processes responsible for the onset and persistence of such flow regimes. In order to establish how air mass transformations over the Gulf Stream affect the large-scale flow we focus on an episode between 20 and 27 of February 2019, when an upper-level ridge established over western Europe - accompanied by an intensified storm track in the North Atlantic. To explore the mechanistic linkage between the formation of this block and air-sea interactions over the Gulf Stream, we adopt a Lagrangian perspective, using backward and forward kinematic trajectories. The detailed investigation of the evolution of potential temperature, moisture, and other variables along the trajectories, as well as of surface fluxes, SST, and SST gradient is carried out to examine the nature of the processes involved in the upper-tropospheric flow variability. Determining the exact geographical location of moisture uptakes as well as their environment allows us to link air-sea interaction processes and the dynamical evolution of the flow. Thereby, we address the hypothesis that air-sea interaction processes over the Gulf Stream, in particular during CAOs, are of fundamental importance for the maintenance of favorable conditions for cyclone intensification and the formation of European blocking.