Summer NAO
The Summer NAO (SNAO) is defined as the first EOF of sea-level pressure over the area 40°N–70°N, 90°W–30°E over 1950–2010 (Folland et al, 2009, Bladé et al, 2011). It only is the dominant mode of variaibility in high summer (July-August) and should not be used outside of summer.