Indian Ocean Dipole Mechanism, Positive & Negative IOD, Impacts

Indian Ocean Dipole

The Indian Ocean Dipole (IOD), which affects the climate of Australia and other countries in the Indian Ocean Basin, is defined as the difference in sea surface temperature between the western pole of the Arabian Sea (western Indian Ocean) and an eastern pole south of Indonesia. Rainfall variability in the neighbouring Indian Oceanic region is greatly influenced by the Indian Ocean Dipole.

What is Indian Ocean Dipole?

The term “Indian Ocean dipole” refers to a phenomenon when two poles of the same substance have opposite qualities. As a result, this geographical occurrence takes place in the Indian Ocean and is related to the sea surface temperatures on two of its sides, each of which has a different temperature profile.

The western Indian Ocean grows warmer (positive phase) and then gets colder (negative phase) than the eastern Indian Ocean during the periodic oscillation of sea surface temperatures known as the Indian Ocean Dipole (IOD), also known as the Indian Nino. The tropical region includes the Indian Ocean.

The ocean’s eastern side has a colder temperature if the western side is warmer. Conversely, if the ocean’s eastern side is warmer, the western side will be cooler. The Indian Ocean Dipole is the name given to this erratic movement in temperature. The Indian Ocean Dipole is the name given to this erratic movement in temperature. It is comparable to the Pacific Ocean’s El Nino and La Nina events.

Indian Ocean Dipole Mechanism

The Indian Ocean, the warmest of the planet’s five oceans, is surrounded by land on three sides. Tropical easterlies impact the water from the Pacific that enters the Indonesian Ocean from the islands of Australia and Indonesia on the eastern side.

Tropical Easterlies move from the northeastern of the northern hemisphere to the southeast of the southern hemisphere. They are found between 0 and 30 degrees latitude. The Indian Ocean is landlocked from the north by the Eurasian Landmass; therefore the arctic seas do not mix with it.

As water from the Pacific Ocean mixes with water from the Indian Ocean, the temperature of the Indian Ocean changes. Variations in the Indian Ocean determine the various IOD phases. The temperature of the surface water is as follows:

• Neutral Indian Ocean Dipole
• Positive Indian Ocean Dipole
• Negative Indian Ocean Dipole

Neutral Indian Ocean Dipole

In the spring, when the sun’s rays are evenly distributed throughout the northern and southern hemispheres, the Neutral Indian Ocean Dipole phase starts. This causes easterlies to flow between 0 and 30 degrees North and South of the equator. These Easterlies/Trade winds have an impact on the ocean’s surface temperature. The temperature is uniformly spread in both the eastern and western Indian Oceans when warm water from the Pacific Ocean interacts with water from the Indian Ocean. This phase is known as the Indian Ocean Dipole’s Neutral Period (IOD).

Positive Indian Ocean Dipole

Because the westerly winds above the equator lessen during this period, warm water might flow to Africa. Changes in the winds also allow for a surge of cold water to move from the deep ocean to the east. This causes temperature disparities in the tropical Indian Ocean, with the east experiencing colder than usual water and the west enjoying warmer than usual water. It has been concluded that this occurrence will be advantageous to the monsoon. A positive dipole in the Indian Ocean is the result.

Negative Indian Ocean Dipole

During this phase, warmer water gathers towards Australia as the westerly winds along the equatorial line intensify. This causes temperature variations in the tropical Indian Ocean, with warmer-than-average water in the east and cooler-than-average water in the west. The monsoon’s progress through India is hampered by this phenomenon.

Indian Ocean Dipole Effects on Indian Monsoon

According to studies, central India receives more rain than typical in an IOD year. It has been demonstrated that in different ENSO years, such as 1983, 1994, and 1997, a high IOD index typically cancels out the influence of ENSO, increasing monsoon rainfall. The eastern pole of the IOD, which is near Indonesia, and the western pole, which is off the coast of Africa, were also found to have independent and cumulative effects on the amount of rain that fell on the Indian subcontinent during the Monsoon..

There is a connection between below-normal SST in the eastern Indian Ocean and higher-than-normal rainfall in the centre of India. On the other side, a negative IOD causes a severe drought when it interacts with El Nino. The Arabian Sea has more cyclones than usual as a result of Positive IOD. Negative IOD results in stronger than usual cyclogenesis (the production of tropical storms) in the Bay of Bengal. In the Arabian Sea, cyclogenesis is lessened during this period. The IOD and Monsoon phenomenon, however, has an oddity.

Indian Ocean Dipole Impacts on India

Strong IOD effects in 1997 and 1998 led to exceptionally heavy monsoons in the Indian Subcontinent. Due to a large positive IOD, this happened. A similar thing occurred in 2006. There have been about 12 positive IODs since 1980, however, only one big negative IOD since 1980 occurred in 2010. Positive IOD tests occurring repeatedly are unusual and extremely concerning because they contributed to the Black Saturday bushfires.

When a positive IOD with La Nina was built in 2007, it was a highly exceptional occurrence. Given that it had only occurred once before, in 1967, this was important (as per the historical records after discovery). Catastrophic flooding in Queensland in 2010–2011 and in Victoria in 2011 was caused by a severe negative IOD that built up and was exacerbated by a potent La Nina.

These trails of succeeding positive IODs are anticipated to occur at least twice every 1000 years, according to forecasting and modelling. The twentieth century also reveals a rise in the strength, frequency, and prevalence of positive IODs.

Indian Ocean Dipole FAQs

Q) What is the Indian Ocean Dipole?

Ans. The difference in sea surface temperature between two regions (or poles, hence a dipole) – a western pole in the Arabian Sea (western Indian Ocean) and an eastern pole in the eastern Indian Ocean south of Indonesia – is what is known as the Indian Ocean Dipole (IOD).

Q) What’s the Indian Ocean Dipole and why is it important?

Ans. The Indian Ocean Dipole, or IOD, refers to long-term variations in the disparity between the tropical western and eastern Indian Ocean’s sea surface temperatures. One of the major factors influencing Australia’s climate is the IOD, which can have a big impact on agriculture.

Q) What is Indian Ocean Dipole 2022?

Ans. The Indian Ocean Dipole (IOD) is defined by the difference in sea surface temperatures between the eastern and western tropical Indian oceans. A negative phase typically sees above-average winter-spring rainfall in Australia, while a positive phase brings drier-than-average seasons.

Q) Which Indian Ocean Dipole is good?

Ans. The negative phase of the IOD is driven by cooler-than-normal SSTs off the coast of Africa and warmer-than-normal SSTs to the west of Indonesia. This configuration of surface sea temperatures gives normal circulation a boost.

Q) Why is IOD important?

Ans. A positive IOD leads to greater monsoon rainfall and more active (above normal rainfall) monsoon days in the Indian sub-continent while a negative IOD leads to less rainfall and more monsoon break days (no rainfall).

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