Context: As per the World Meteorological Organisation (WMO), La-Nina weather, which brings heavy rain and floods to India, may develop in the next three months but it is expected to be relatively weak and short-lived.
Relevance of the Topic:Prelims: La-Nina; Impact of La Nina (India & Globally)
La Nina
- It basically refers to an abnormal cooling of the central and eastern Pacific Ocean waters off the coasts of Ecuador and Peru.
- Such cooling (sea surface temperatures i.e. SSTs falling) is a result of strong trade winds blowing west along the equator, taking warm water from South America towards Asia.
- The warming of the western equatorial Pacific, then, leads to increased evaporation and concentrated cloud-formation activity around that region, whose effects may spread to India as well.
Normal Condition:
- Winds along the equator push warm water westward (from South America to Indonesia). As the warm water moves west, cold water from the deep rises up to the surface (on the coast of South America).
La Niña year:
- Stronger than usual winds makes the water in the Pacific Ocean near the equator a few degrees colder. La Niña blows warm water to the western Pacific. This means that places like Indonesia and Australia can get much more rain than usual.
Impact of La Nina in India:
- La Nina events usually lead to warming of the Indian Ocean, particularly the Western Indian Ocean region due to changes in wind patterns. This also leads to reduced upwelling in the region leading to reduced fisheries catch.
- Monsoon Enhancement: Usually La Niña events lead to strengthening of monsoons in India leading to more rainfalls.
- Boost for Agriculture: An enhanced monsoon can benefit agriculture, especially in regions where rainfed agriculture is practiced.
- Flood Risks: Increased rainfall can also result in flooding events in low-lying areas leading to damage to life & property.
- Winter Temperatures: During La Niña years, northern India may experience colder winters. This is due to a stronger high-pressure system over Central Asia, which can bring cold winds down into the northern plains of India.
- Drought Mitigation: La Niña conditions can help alleviate drought situations in regions experiencing water scarcity, as the increased rainfall can replenish reservoirs, rivers, and groundwater levels.
Impact of La Nina (Globally)
Global Variations:
- Regions lying in western pacific (Australia, Indonesia, Philippines etc) experiences wetter than average conditions, leading to increased rainfall and sometimes flooding in parts of the country.
- La Niña can bring variable impacts to different parts of South America. In countries like Argentina and Brazil, it can lead to wetter conditions in some regions, benefiting agriculture with increased crop yields. However, in other areas such as parts of Bolivia and Paraguay, drought conditions may prevail, negatively impacting crop production.
- In North America it often results in a more active winter storm track across the northern United States and Canada, leading to increased snowfall and colder temperatures. Conversely, the southern United States tends to experience warmer and drier conditions, which can increase droughts risks in already arid regions like the southwestern states.
Economic Impact:
- Energy Sector: La Niña can influence energy markets globally. For instance, in regions where La Niña results in increased hurricane activity, such as the Gulf of Mexico and the Caribbean, disruptions to oil and gas production can occur, leading to fluctuations in energy prices.
- Upwelling along the Pacific Coast of South America during La Nina brings cold deep nutrient rich water to the surface, promoting phytoplankton growth leading to boom in fish population in eastern Pacific.
- Commodities: Agricultural commodities such as grains (corn, soybeans) and soft commodities (coffee, cocoa) can see price volatility due to changes in production caused by La Nina induced weather patterns.
Social and Environmental consequence:
- Small island nations in the Pacific can be particularly vulnerable to the impacts of La Niña, including increased storm surges, coastal erosion, and damage to infrastructure due to Intensified tropical cyclones.
Ecological Effects:
- La Niña alters ocean temperatures and currents, affecting marine life distribution and productivity
Health Implications:
- La Niña can influence the spread of vector-borne diseases such as malaria and dengue fever. Increased rainfall can create breeding grounds for mosquitoes, potentially leading to outbreaks in affected regions.