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Indian Ocean Dipole

Date: 24 January 2020 Tags: Geography & Environment

Issue

Australia is facing raging bushfires across its vast grasslands, which it terms to be an effect of severe drought caused due to alterations in Indian Ocean Dipole(IOD). In this context it is necessary to understand the phenomenon of IOD.

 

Details

  • The Indian Ocean Dipole (IOD), also known as the Indian Niño, is an irregular oscillation of sea surface temperatures in which the western Indian Ocean becomes alternately warmer (positive phase) and then colder (negative phase) than the eastern part of the ocean.

  • The IOD involves an aperiodic oscillation of sea-surface temperatures (SST), between "positive", "neutral" and "negative" phases.

  • A positive phase sees greater-than-average sea-surface temperatures and greater precipitation in the western Indian Ocean region, with a corresponding cooling of waters in the eastern Indian Ocean, which tends to cause droughts in adjacent land areas of Indonesia and Australia.

  • The negative phase of the IOD brings about the opposite conditions, with warmer water and greater precipitation in the eastern Indian Ocean, and cooler and drier conditions in the west.

  • The IOD also affects the strength of monsoons over the Indian subcontinent.

  • The research shows that when the IOD is in its negative phase, with cool western Indian Ocean water and warm water off northwest Australia (Timor Sea), winds are generated that pick up moisture from the ocean and then sweep down towards southern Australia to deliver higher rainfall.

  • In the IOD-positive phase, the pattern of ocean temperatures is reversed, weakening the winds and reducing the amount of moisture picked up and transported across Australia.

  • The consequence is that rainfall in the south-east is well below average during periods of a positive IOD.

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