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Global warming alters rainfall rhythm {Environment}

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Global warming has altered a key weather system and that may be whetting cyclones in the Bay of Bengal, decreasing winter rain in north India and altering global rainfall patterns, a study by a team of Indian and U.S. researchers has found.
How it is affecting the rainfall pattern?

  • The Madden–Julian Oscillation (MJO), as it’s called, is a moving band of rain clouds that travels around the globe spanning 12,000–20,000 km across the tropical oceans.
  • In its journey, it interacts with surface waters of the Indo-Pacific Ocean, the largest pool of warm water in the globe, and due to this the lifecycle of the MJO gets affected.
  • The MJO clouds on average are spending only 15 days, instead of 19, over the Indian Ocean.
Madden–Julian Oscillation
  • The Madden-Julian Oscillation (MJO) is a global-scale feature of the tropical atmosphere.
  • The MJO is the major fluctuation in tropical weather on weekly to monthly timescales. The MJO can be characterized as an eastward moving "pulse" of cloud and rainfall near the equator that typically recurs every 30 to 60 days. However, the signal of the MJO in the tropical atmosphere is not always present.
  • MJO effects are most evident over the Indian Ocean and western equatorial Pacific. It influences the timing, development and strength of the major global monsoon patterns, including the Indian and Australian monsoons.
  • Tropical cyclones are also more likely to develop in association with certain phases of a strong MJO event.
Image result for Madden–Julian Oscillation
How Does MJO Affect Indian Monsoon?
  • The Indian Ocean Dipole (IOD), El Nino and MJO are all oceanic and atmospheric phenomena, which affect weather on a large scale. IOD only pertains to the Indian Ocean, but the other two affect weather on a global scale-up to the mid-latitudes.
  • IOD and El Nino remain over their respective positions, while MJO is a traversing phenomenon.
  • The journey of MJO goes through eight phases.
    • When it is over the Indian Ocean during the Monsoon season, it brings good rainfall over the Indian subcontinent.
    • On the other hand, when it witnesses a longer cycle and stays over the Pacific Ocean, MJO brings bad news for the Indian Monsoon.
  • It is linked with enhanced and suppressed rainfall activity in the tropics and is very important for the Indian monsoonal rainfall.

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