NORTHEAST MONSOON

NORTHEAST MONSOON

Subject: Geography

Context: The southern states recorded normal rainfall during the recently concluded Northeast monsoon season, the India Meteorological Department (IMD) has said.

Kerala, however, ended with a 26 per cent deficit of rainfall this season.

Concept :

• In 2020, the onset of the Northeast monsoon, also known as winter monsoon, was delayed by 10 days over Tamil Nadu and Puducherry and was realised on October 28.
• The season began on a good note but soon lost steam in November.
• The Northeast monsoon came under the influence of weak La Nina conditions along with the neutral phase of the Indian Ocean Dipole (IOD).

Northeast Monsoon

• The Northeast monsoon occurs during October to December.
• It is confined to the Southern peninsula.
• It is also called the winter monsoon.
• Northeast monsoon is important for Tamil Nadu, Puducherry, Karaikal, Yanam, coastal Andhra Pradesh, Kerala, north interior Karnataka, Mahe and Lakshadweep.
• Tamil Nadu records about 48% of its annual rainfall during these months, making it the key factor for undertaking agricultural activities.
• Some South Asian countries such as Maldives, Sri Lanka and Myanmar, too, record rainfall during October to December.

La Niña

• La Niña (Spanish for ‘little girl’) refers to the large-scale cooling of the ocean surface temperatures in the central and eastern equatorial Pacific Ocean, along with changes in the tropical atmospheric circulation.
• It usually has the opposite impacts on weather and climate as El Niño, which is the warm phase of the so-called El Niño Southern Oscillation (ENSO).

Indian Ocean Dipole

• IOD is the difference between the temperature of eastern (Bay of Bengal) and the western Indian Ocean (Arabian Sea).
• This temperature difference results into pressure difference which results in flowing of winds between eastern and western parts of Indian Ocean.
• IOD develops in the equatorial region of Indian Ocean from April to May peaking in October.
• A ‘positive IOD’ — or simply ‘IOD’ — is associated with cooler than normal sea-surface temperatures in the eastern equatorial Indian Ocean and warmer than normal sea-surface temperatures in the western tropical Indian Ocean.
• The opposite phenomenon is called a ‘negative IOD’, and is characterised by warmer than normal SSTs in the eastern equatorial Indian Ocean and cooler than normal SSTs in the western tropical Indian Ocean.