Indian Ocean Dipole (IOD) is an atmosphere-ocean coupled phenomenon in the Indian Ocean, characterised by a difference in sea-surface temperatures. IOD is the difference between the temperature of eastern (Bay of Bengal) and the western Indian Ocean (Arabian Sea). Indian monsoon depends upon not only El Nino La Nina but also IOD and other such ocean phenomena.

1. Indian Ocean Dipole

2.  An atmosphere-ocean coupled phenomenon
in the Indian Ocean, characterized by a
difference in sea-surface temperatures.
 It is the difference between the temperature
of eastern (Bay of Bengal) and the
western Indian Ocean (Arabian Sea).
 Indian monsoon depends upon not only El
Nino La Nina but also IOD.

3. Characteristics of IOD
1. Temperature difference: IOD occurs because
of temperature difference which results into
pressure difference which results in flowing of
winds between eastern and western parts of
Indian Ocean.
2. Development: IOD develops in the equatorial
region of Indian Ocean from April to May,
peaking in October.
3. Three Phases: The IOD has three phases such as
Neutral, Positive and Negative IOD.

5. Neutral Phase of IOD
Water flows from the Pacific
between Indonesia’s islands,
keeping seas warm to the
northwest of Australia.
Air rises above this area and falls
across the western half of the
Indian Ocean basin, blowing
westerly winds along the equator.

7. Positive Phase of IOD:
 Westerly winds weaken along the equator,
allowing warm water to move to Africa.
 Changes in the winds also allow a rise of cool
water from the deep ocean in the east.
 This creates a temperature difference across the
tropical Indian Ocean with cooler than normal
water in the east and warmer than normal water
in the west.
 This event has been found to be beneficial
for the monsoon.

9. Negative Phase of IOD:
 westerly winds intensify along the equator,
allowing the concentration of warmer
waters near Australia.
 This creates a temperature difference across
the tropical Indian Ocean, with warmer
than normal water in the east and cooler
than normal water in the west.
 This event obstructs the progression of
monsoon over India.

11. Impact on Southwest Monsoon
 Increased rainfall due to positive IOD: positive
IOD year sees more than normal rainfall over
central India. positive IOD index often negated the
effect of El Nino Southern Oscillation (ENSO),
resulting in increased Monsoon rains in several
ENSO years.
 Droughts Due to negative IOD: complements El
NiNo leading to severe drought.
 Cyclones: positive IOD results in cyclones than
usual in Arabian Sea. Negative IOD results in
stronger than usual cyclogenesis in the Bay of
Bengal.

13. Thank You
Bibliography
•https://blog.forumias.com/answeredwhat-is-the-indian-ocean-
dipole-what-are-its-characteristic-features-discuss-its-impact-on-
indian-monsoon/
• www.Climate.gov
•www.climatekelpie.com.au