El Nino Occurrences of over 400 Years

  • A study has tracked El Niño occurrences of over 400 years.
  • The El Niño trends of the past have been studied on the basis of coral cores spanning the Pacific Ocean.
  • Coral cores — like tree rings and ice cores — have centuries-long growth patterns and contain isotopes that can tell us a lot about the climate of the past.
  • El Niños are linked to extreme weather across the globe, with particularly profound effects on precipitation and temperature extremes in Australia, South East Asia and the Americas.
  • Hence, the study is expected to strengthen the science of predicting extreme weathers and plan better.

Finding of the Study

  • El Niños have become stronger and their pattern too has been changing.
  • The trend of El Niño in the last four centuries shows a variation in El Niño types.
  • There has been an increase in central Pacific events (El Niño Modoki) lately.
  • The most recent 30-year period includes fewer, but more intense, eastern Pacific El Niño events.

Madden-Julian Oscillation (MJO)

  • MJO is an eastward moving pulse of cloud & rainfall in the tropics that recurs every 30 to 60 days.
  • Unlike ENSO, which is stationary (in Pacific Ocean), the MJO is an eastward moving disturbance.
  • ENSO is associated with persistent features that last several seasons over the Pacific Ocean basin.
  • On the other hand, multiple MJO events occur within a season (i.e. weather varies on a week-to-week basis).
  • The MJO consists of enhanced rainfall convective phase and suppressed rainfall convective phase.
  • These two phases produce opposite changes in rainfall and this entire dipole propagates eastward.

Madden-Julian Oscillation impact on Weather

  • The MJO can modulate the timing and strength of monsoons.
  • The MJO can influence tropical cyclone numbers and strength in nearly all ocean basins.

The MJO can result in jet stream changes that can lead to cold air outbreaks, extreme heat events, and flooding rains over North America