North Atlantic Oscillation (RPCA daily)

CPC-method rotated-PCA North Atlantic Oscillation pattern rebuilt from ERA5 500-hPa height, daily least-squares fit on patterns interpolated to the day. Positive: low heights over Greenland, high over the central North Atlantic (35–40°N), eastern US and western Europe. — Barnston & Livezey 1987; NOAA CPC