The dynamical link between surface cyclones, upper-tropospheric Rossby wave breaking and the life cycle of the Scandinavian blocking
Michel, Clio ; Rivière, Gwendal ; Terray, L. ; Joly, Bruno
The Scandinavian blocking (SB) is a well-known quasi-stationary state of the atmospheric flow and one of the four main weather regimes over the Euro-Atlantic domain in winter. The aim of our study is to analyze the link between surface cyclones, upper-tropospheric Rossby wave breakings and the life cycle of SB using ERA-40 reanalysis. The onset and decay of SB are studied by considering the preferential transitions from the zonal regime to SB and from SB to the Greenland anticyclone regime. During the SB onset, Atlantic cyclones have straight trajectories that extend toward the north of Scandinavia. These surface cyclones are associated with anticyclonic wave breakings in the upper troposphere over Europe. During the SB decay, cyclones are much less present in the eastern part of the Atlantic and most of them present curved trajectories in mid-Atlantic. They are shown to be linked to cyclonic wave breakings to the south of Greenland.
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