Indian Ocean Dipole, also known as IOD, is among the most peculiar climatic events that geographically impacts the Indian Subcontinent. IOD is responsible for affecting the international climatic phenomena, as well as the southwest rainfall in India.
If we observe previous years UPSC Mains papers, the geographical characteristics and locations account for almost 7% to 14% of marks weightage. Therefore, IOD becomes one of the important topics concerning UPSC mains and prelims perspective.
The questions that come under this topic are quite forthright. It is very easy to answer such types of questions. According to the UPSC experts, one must include diagrams in all given Indian Ocean dipole questions, as it will not only impress the checker but will also help you gain full or maximum marks possible.
In this article, you can find the answers to how IOD impacts the monsoon pattern in India. Read on to know more.
What is Indian Ocean Dipole?
A phenomenon resulting due to the coupling effect between the atmosphere and ocean in the tropical region of the Indian Ocean is known as Indian Ocean Dipole or IOD. The variance in temperature between the sea and the surface is the prominent factor of this phenomenon. Other than El Nino and La Nina, the monsoon pattern in India depends on IOD to a great extent.
Phases of the Indian Ocean Dipole
The segregation of IOD includes three phases of IOD, i.e., negative IOD, neutral IOD, and positive IOD. All these phases have a distinct effect on the monsoon pattern in India. The details of each phase of IOD is as follows:
Positive Indian Ocean Dipole
In a positive IOD, the eastern region of the equatorial Indian Ocean becomes cooler than the usual temperature. On the other hand, the western part of the tropical region of the Indian Ocean becomes remarkably warmer. This kind of effect due to a positive IOD is favourable for the monsoon pattern in India.
Negative Indian Ocean Dipole
This phase is exactly the opposite phenomenon of positive IOD. The eastern region of the equatorial Indian Ocean becomes exceptionally hot. However, the western part of the tropical region of the Indian ocean becomes comparatively cooler. This influences obstacles in the rainfall pattern throughout India.
Neutral Indian Ocean Dipole
In the case of neutral IOD, the flow of water is from the Pacific, resulting in warmer seas towards the northwestern region of Australia. The air extends over this region and drops over the partial part of the western region in the Indian Ocean. This concludes in the whirling westerly winds adjacent to the equator.
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Impact of Positive IOD in 2019
The tremendous amount of rainfall from August to September 2019 broke all the records in India. In the initial parts of June, India experienced a 30% shortfall. However, till the end of the monsoon per IOD, India observed over 10% extra rainfall. This was a surprise for many of the researchers, as such an unparalleled rainfall event took place after 88 years.
In this peculiar year, the rainfall was the highest in September since the year 1917. The comprehensive annual rainfall of 2019 was the highest since the year 1994.
Strongest IOD ever
The IOD recorded in the year 2019 was one of the strongest positive IOD in India. The positive IOD in 2019 had significantly become robust in September. The researchers were therefore keen to study more about this strong and record-breaking positive IOD effect. Since 2019, the association of strong positive IOD with heavy rainfalls has been pretty prominent.
Initial Monsoon Records
Due to powerful positive IOD, 100% normal rainfall and similar series of events took place in 1997 and 2006. It’s astonishing, as the 1997 year was an El Nino year, but due to robust IOD in that peculiar year, the impact of El Nino wasn’t effective. In 2019, positive IOD was strongest in September. This effect of this IOD was experienced right from June, and is the most robust IOD ever in the Indian summer pattern of monsoon.
Points to Remember
These were some of the key points of the questions related to IOD in the Civil Service Examination. You need to be very careful while mentioning the details of the Indian Ocean dipole and Indian monsoon in UPSC. The diagrams of this phenomenon are of utmost importance; hence you should also consider practising it thoroughly.
However, the questions asked for this particular topic are quite easy and straightforward. You can easily score marks for this particular topic if you understand the concepts well. It is an easy scoring topic in mains as well as in prelims. Therefore, do not ignore the IOD topics as well as their impact on Indian Monsoon.
Despite the association of IOD with the Indian monsoon pattern, the researchers do not hold IOD as the solely responsible phenomenon. This is because IOD’s correlation with the monsoon pattern in Indian summer is quite weak, and rather questionable, since IOD is not the only phenomenon on which the Indian Monsoon pattern is dependent.
It has a lesser influence on the Indian Monsoon than that of ENSO, aka El Nino Southern Oscillation. Moreover, the study on the effect of IOD on the Indian Monsoon pattern is not yet entirely clear. However, the impact of IOD can not be completely neglected, as there are some proven facts about positive IOD influencing heavy rainfall.
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