Impact of La-Nina on Indian Monsoon
- The La Niña phase of the equatorial Pacific Ocean may persist for 6 more months - one of the longest ever La Niña events in recorded history.
- The third episode since 1950 to stretch into a third year.
- May have wide-ranging implications across the world and can potentially aggravate both floods and droughts in regions.
El-nino and La-nina
- The periodic warming and cooling of surface waters in the equatorial Pacific Ocean (El Niño Southern Oscillations/ ENSO) has a major influence on global weather patterns, including the Indian monsoon.
- La Niña - ENSO phase in which sea-surface temperatures are cooler than normal.
- Warmer phase - El Niño.
- El Niño and La Niña have almost opposite impacts on weather events.
- El Niño and La Niña episodes last for about 9 months to a year.
- Usually develop in the March-June period
- Strongest during winter (November-January in the northern hemisphere)
- Weakens by March or April of next year.
- However, sometimes they continue for much longer periods.
‘Triple dip’ La Niña
- The El Niño of 2015-16, spread over 19 months, was one of the longest on record.
- The current La Niña episode has already surpassed that in length.
- Started in September 2020
- Set to continue for another six months
- Classified as a ‘triple dip’ La Niña.
Impact of La Nina
- In the Indian context, La Niña is associated with good rainfall during the monsoon season.
- A continued spell of La Niña could lead to expectation of another year of good, or normal, rainfall during the monsoon.
- The continuance of La Niña further into 2023 is not bad news from the Indian standpoint.
- But it is not the same for many other regions where La Niña has very different impacts.
Climate change link
- The occurrences of El Niño or La Niña are not very regular.
- Sometimes they emerge every two years, at other times there has been a gap of even seven years.
- So, the natural variability of ENSO is not understood very clearly.
- Such events are also linked with global warming.
- During La Niña, the colder surfaces allow the oceans to absorb more heat from the atmosphere.
- Thus, the air temperatures decrease, producing a cooling effect.
- However, this is not enough to reverse or neutralize the impacts of global warming.
Prelims Takeaway
- El Nino
- La Nina
- ENSO