Azores/Iceland NAO Dataset Advantages

This dataset produces very realistic estimates of the magnitude of the NAO dipole during non-winter seasons. This is because the subtropical center at the Azores lies in the eastern Atlantic Ocean, the region actually occupied by the subtropical anticyclone during the northern warm season. The Azores center of action produces an NAO index better representative of the strength of the Atlantic westerlies in these seasons than is accomplished using European land-based station-pressure centers. The better performance of an Azores-based NAO index in showing the NAO dipole characteristics in non-winter seasons is demonstrated in Table 1 of Hurrell and van Loon (1997).