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Current Affairs

Weak north-east monsoon

Date: 25 November 2020 Tags: Geography & Environment

Issue

Rainfall over the Southern peninsular region due to north-eastern region has been subdued so far. The reason is a prevalent La Niña condition, along with a low pressure belt that is currently lying to the north of its normal position.

 

 

Background

Also called the winter monsoon, the rainfall associated with the Northeast monsoon is important for Tamil Nadu, Puducherry, coastal Andhra Pradesh, Kerala, north interior Karnataka and Lakshadweep.

 

Details

  • India receives rainfall during two seasons. About 75 percent of the country’s annual rainfall is received from the Southwest monsoon between June and September.

  • The Northeast monsoon, on the other hand, occurs during October to December, and is a comparatively small-scale monsoon, which is confined to the Southern peninsula.

  • Tamil Nadu records about 48 percent during these months, making it the key factor for undertaking agricultural activities and reservoir management in the state.

  • The India Meteorological Department (IMD) had forecast below normal rainfall over Tamil Nadu and normal rainfall over the southern peninsula for the current season.

 

North-east monsoon

  • After the complete withdrawal of the Southwest monsoon from the country takes place by mid-October, the wind pattern rapidly changes from the south-westerly to the north-easterly direction. 

  • The winds associated with the formation of low pressure systems, depressions, or cyclones influence this monsoon, and therefore, the rainfall.

 

La Nina

  • La Niña refers to the large-scale cooling of the ocean surface temperatures in the central and eastern equatorial Pacific Ocean, coupled with changes in the tropical atmospheric circulation.

  • Together, the El Niño and La Niña phenomena are termed as El Niño Southern Oscillation (ENSO). These are large-scale ocean phenomena which influence the global weather — winds, temperature, and rainfall.

  • They have the ability to trigger extreme weather events like droughts, floods, hot and cold conditions, globally.

 

La Nina and north-east 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 low pressure or cyclones formed in the Bay of Bengal remain significantly to the north of their normal position.

  • 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.

  • The current position of the Inter Tropical Convective Zone (ITCZ) has also contributed to the poor rainfall during the ongoing monsoon season.

  • The ITCZ is a low-pressure belt, whose northward and southward movements along the equator determine the precipitation in the tropics. Currently, the ITCZ is located to the north of its normal position.