Context: The rainfall over the Southern peninsular of India - region receiving the majority of its rainfall as a result of Northeast monsoon has been deficient so far.
More on the news: 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.
About the Northeast monsoon:
Source: JV IAS
- Two seasons of rainfall in India:
- Southwest monsoon (about 75 percent of the country’s annual rainfall) between June and September and
- Northeast monsoon during October to December.
- Affected region: Also called the winter monsoon, it is a comparatively small-scale monsoon, which is confined to the Southern peninsula - Tamil Nadu, Puducherry, Karaikal, Yanam, coastal Andhra Pradesh, Kerala, north interior Karnataka, Mahe and Lakshadweep.
- Tamil Nadu records about 48 percent of its annual rainfall during these months.
- Withdrawal of the Southwest monsoon: After this, by mid-October the wind pattern rapidly changes from the south-westerly to the north-easterly direction.
- Peak time for cyclonic activity: From October to December is the peak time for cyclonic activity in the North Indian Ocean region - covering the Arabian Sea and the Bay of Bengal.
- Low pressure system: The winds associated with the formation of low pressure systems, depressions, or cyclones influence this monsoon, and cause rainfall.
La Niña and El Nino:
Source: Public Citizen
- El Niño (Spanish for ‘little boy’):
- It is the abnormal surface warming observed along the eastern and central regions of the Pacific Ocean - region between Peru and Papua New Guinea.
- The expression is heard more commonly in India.
- La Niña (Spanish for ‘little girl’): It is an abnormal cooling of these surface waters.
- ENSO: Together 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.
- Connection between La Niña and the Northeast monsoon:
- Negative impact on 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.
- Reason: During La Niña years, the low pressure or cyclones formed in the Bay of Bengal remain significantly to the north of their normal position.
- Position of the Inter Tropical Convective Zone (ITCZ): Its current position 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.
Image Source: The Financial Express