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Why has the Northeast monsoon remained subdued this year?

Topics Covered: Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc.

Why has the Northeast monsoon remained subdued this year?


Context:

Rainfall over the Southern peninsular region has been deficient so far.

The reason is:

  1. Prevalent La Niña condition, along with a low pressure belt that is currently lying to the north of its normal position.
  2. The current position of the Inter Tropical Convective Zone (ITCZ).

What is La Nina?

La Niña (Spanish for ‘little girl’) is an abnormal cooling of eastern and central regions of the Pacific Ocean surface waters.

  • Together, the El Niño and La Niña phenomena are termed as El Niño Southern Oscillation (ENSO).
  • These are large-scale ocean phenomena which inflence the global weather — winds, temperature and rainfall.
  • They have the ability to trigger extreme weather events like droughts, floods, hot and cold conditions, globally.

Each cycle can last anywhere between 9 to 12 months, at times extendable to 18 months — and re-occur after every three to five years.

What is the Northeast monsoon?

  • Occurs during October to December, and is a small-scale monsoon compared to South- West Monsoon.
  • It is confined to the Southern peninsula.
  • The rainfall associated with the Northeast monsoon is important for Tamil Nadu, Puducherry, Karaikal, Yanam, coastal Andhra Pradesh, Kerala, north interior Karnataka, Mahe and Lakshadweep.
  • Some South Asian countries such as Maldives, Sri Lanka and Myanmar, too, record rainfall during October to December.

But how is La Niña linked with the Northeast monsoon?

While La Niña conditions enhance the rainfall associated with the Southwest monsoon, it has a negative impact on rainfall associated with the Northeast monsoon.

During La Niña years, the synoptic systems — low pressure or cyclones — formed in the Bay of Bengal remain significantly to the north of their normal position.

  • Besides, instead of moving westwards, these systems recurve. As they lie to the north of their normal position, not much rainfall occurs over southern regions like Tamil Nadu.

la_nina

InstaLinks:

Prelims Link:

  1. What is El Nino?
  2. What is La Nina?
  3. What is ENSO?
  4. When do these events occur?
  5. Impact of ENSO on Asia, Africa and Australia.

Mains Link:

Discuss the impact of La Nina weather phenomenon on India.

Sources: Indian Express.