Spatially and temporally large-scale anomalies that influence the variability of the atmospheric circulation
  • Arctic Oscillation (AO)
    Information on the Arctic Oscillation (AO), a large scale mode of climate variability, also referred to as the Northern Hemisphere annular mode.
  • El Niño/Southern Oscillation (ENSO)
    Information on the El Nino Southern Oscillation (ENSO), a periodic fluctuation in sea surface temperature and air pressure in the equatorial Pacific Ocean.
  • North Atlantic Oscillation (NAO)
    Information on the North Atlantic Oscillation (NAO) index, which is based on the surface sea-level pressure difference between the Subtropical (Azores) High and the Subpolar Low.
  • Pacific Decadal Oscillation (PDO)
    Information on the Pacific Decadal Oscillation (PDO), often described as a long-lived El Nino-like pattern of Pacific climate variability.
  • Pacific-North America Index (PNA)
    Information the Pacific-North America (PNA) pattern, one of the most prominent modes of low-frequency variability in the Northern Hemisphere extratropics, appearing in all months except June and July.