Er zijn 40 events geanalyseerd, waarvan 19 splits. Het patroon boven Europa wat T2m betreft is niet zo sterk, en ook niet significant. Wat interessanter is, is dat bij displacements blokkades vooral vormen boven Canada, terwijl die bij splits boven Groeland en N-Europa vormen.
Over displacements:
Preceding these events are often anomalously low pressure systems over North America and high pressure systems over western Europe and the Pacific. Associated with this are warm temperature anomalies over Northern America and an increase in blocking over northern Eurasia.
While the stratospheric NAM anomaly is large for these events, with a potential for predictability up to a month before hand, the anomaly is not seen to descend through the troposphere. At the surface the AO trend is similar around the onset date for both splits and displacements, although the AO anomaly persists for ~15 days less during displacements.
The largest surface impact from displacement is observed over the month following an event and shows anomalously cold temperatures of magnitude −1.5 K over North America, a feature that is not observed for the splitting case. Associated with this, increased blocking activity is observed over Canada.
Over splits:
Preceding splitting events are anomalously low temperatures over Eurasia, with a wave-2-like pattern observed in MSLP.
The midstratospheric NAM signal following splitting events is weaker than that which follows displacements events, but importantly anomalies can descend from the midstratosphere to the surface, unlike displacement events. The evolution of the anomalies are also far more barotropic than during displacement events.
For 60 days following a splitting event a coherent negative AO anomaly is observed. Consistent with this, high-latitude blocking in both the Atlantic and Pacific basins increases while blocking in the mid-Atlantic, Europe, and western Eurasia decreases. Ultimately the largest effect from these events is observed over northern Eurasia with low temperature anomalies of up to −3 K.