Tropical plumes (TPs) are elongated upper-level cloud bands that stretch from the Tropics pole- and eastward, accompanied by a strong subtropical jet streak and an upper-level extratropical disturbance. They are a visible sign of interactions between the tropical and the extratropical circulations and have been studied with respect to their climatology, dynamics and precipitation. Relying on ECMWF re-analysis and satellite data, this project deals with an analysis of the role of TPs in the hemispheric energy and momentum budget of the northern hemisphere. This includes an examination of the implications for subseasonal variability (weather-climate connection), the North Atlantic Oscillation and extreme sensible weather events.

The penetration of an upper-level potential vorticity (PV) anomaly to low latitudes is an important ingredient in many situations of tropical-extratropical interactions. Various statistical studies have related this process to linear Rossby wave propagation. Observational case studies have presented evidence for an additional crucial role of diabatic processes related to upstream explosive baroclinic developments in amplifying and eventually breaking the PV wave. Focusing on the North Atlantic, this project aims at quantifying the influence of the latter process through numerical sensitivity experiments with the Lokalmodell (LM) of the German Weather Service (DWD).