Other Large-Scale Oscillations: NAO and PDO

• Besides ENSO, scientists have discovered other large-scale oscillations of common meteorological variables (such as pressure) in other parts of the world.
• Two well-known oscillations are the North Atlantic Oscillation (NAO) and the Pacific Decadal Oscillation (PDO)

NAO:

• refers to pressure variations associated with the Icelandic low and subtropical high pressure near the Azores
  • If the Icelandic low and Azores subtropical high are stronger than normal, then the NAO is positive
    • results in more and stronger storms crossing the Atlantic on a more northerly track
    • eastern US will experience mild and wet winter conditions
  • If the Icelandic low and Azores subtropical high are weaker than normal, then the NAO is negative
    • results in fewer and weaker storms crossing the Atlantic
    • eastern US experiences more cold-air outbreaks and snowy weather conditions
• Here is a map of the NAO index since 1950.