Séminaire
The impact of the atmospheric blocking activity over the Euro-Atlantic sector is investigated in the NCEP/NCAR Reanalysis and in the CMCC coupled atmosphere-ocean models. This is carried out through a detailed analysis of the relationships between blocking occurrence, the Atlantic eddy-driven jet stream displacements and the main teleconnection patterns variability over the region. In order to study the properties of blocking, we make use of a bidimensional blocking index based on geopotential height and a series of related diagnostics. We therefore address the relationship between the North Atlantic Oscillation (NAO) and the blocking occurrence, confirming the tight coupling seen in previous works between blocking over Greenland (Greenland Blocking) and the negative phase of the NAO. On the other side, blocking events over Europe (European Blocking) emerge as not being correlated with the NAO. Moreover, we found that Greenland Blocking is linked with the equatorward displacements of the jet streams, and that European Blocking is associated with the poleward displacements of the jet (and only in some case it leads to a split flow). Interestingly, the combination of GB and EB seems able to satisfactorily explain the majority of the low-frequency variability over the Euro-Atlantic sector.