Indian Ocean Dipole (IOD)

August 24, 2023

GS Paper I Geography

Context:

Recently, Australian Bureau of Meteorology has reported a shift in the Indian Ocean Dipole (IOD) index in recent days.
- The IOD index has increased from +0.34°C to +0.79°C, surpassing the positive IOD threshold of +0.4°C.
- Last Positive IOD event occurred in 2019.

24.4

About Indian Ocean Dipole (IOD):

IOD signifies the fluctuation in sea-surface temperatures from warm to cool in the Indian Ocean area south of Sri Lanka.
The IOD is defined by the difference in sea surface temperature between western Indian Ocean and eastern Indian Ocean south of Indonesia.
The IOD affects the climate of Australia and other countries that surround the Indian Ocean Basin, and is a significant contributor to rainfall variability in this region.

About IOD index:

IOD index is defined as the difference between the mean sea surface temperature in the western Indian Ocean and mean sea surface temperature in the eastern Indian Ocean.
When the IOD index is positive, the phenomenon is referred to as the positive IOD and when it is negative, it is referred to as the negative IOD.

Positive IOD

Negative IOD

Warmer sea surface temperatures in the western Indian Ocean relative to the east.
Indonesia and Australia tend to be drier than normal, which increases the chances of bushfires, while eastern Africa tends to be wetter than normal, increasing the likelihood of floods.
It helps rainfall along the African coastline and also over the Indian subcontinent.
Positive IOD event is known to help the South-West monsoon.

Cooler sea surface temperatures in the western Indian Ocean relative to the east.
Winds become more westerly, bringing increased cloudiness to Australia’s northwest.
Indonesia and Australia tend to be wetter than normal, while eastern Africa tends to be drier than normal.

News Source: Hindu BL

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