Atmospheric Blocking in the CMCC CMIP5 simulations

• Main Authors: Paolo Davini, Chiara Cagnazzo, Elisa Manzini, Silvio Gualdi, Enrico Scoccimarro, Antonio Navarra
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Figure 3; From left to right; Blocking Instensity index; Meridional Gradient; Greenland; Pacific; North Atlantic; North Atlantic oscillation
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.673.3871; http://conference2011.wcrp-climate.org/posters/C34/C34_Davini_W225A.pdf

The adoption of new bidimensional index allows a more detailed study of different physical featurse of blocking events: • Pacific and Greenland blocking shows similar diagnostics (Fig. 3 and 4) and can be considered as high-latitude blocking (HLB) in agreement to the definition by Berrisford et al. (2007). On the other side, European Blocking behaves differently than HLB, showing that just the European one can be considered as a “real ” blocking events and suggesting the possibility that they are governed by different dynamics. • The Euro-Atlantic winter variability, expressed via the JLI (Fig. 5 and 6), can be associated with the occurrence/absence of blocking: this is confirmed by CMCC model bias, even if the impact on the jet is more clear for Greenland blocking than for European blocking. • CMCC models (Fig. 2) show general underestimation of European blocking, even if they possess good representation of the North Atlantic Oscillation. • As European Blocking appears to be not correlated to the phase of the NAO, studying blocking events is a key element to capture the variability over the Euro-Atlantic region in climate simulations. 2. Data and Model simulations Atmospheric blocking describes a mid-latitude weather pattern where a quasi-stationary high-pressure system modifies the westerly flow, “blocking ” (or at least diverting) the eastward movement of the migratory cyclones (Rex, 1950a).