La Niña is a climate phenomenon that can have a significant impact on India’s weather patterns. It occurs when sea surface temperatures in the central and eastern Pacific Ocean are cooler than normal, which in turn affects global weather conditions. For India, La Niña often brings heavier monsoons, leading to above-average rainfall. While this can be beneficial for agriculture, it may also cause flooding in certain regions. Additionally, La Niña tends to lower temperatures across the country, particularly during the winter months. Understanding La Niña is essential for preparing for its varied effects on India’s climate and economy.
Tags: GS-1, Geography-Physical Geography- Geographical Phenomena – Weather & Climate
Context:
- This year’s La Niña, characterised by cooler-than-average sea surface temperatures in the central Pacific, significantly influences India’s climate by enhancing monsoon activity, often resulting in above-average rainfall.
- During this year’s 2024 La Niña event, India will experience a 12% excess in monsoon rainfall and It also contributes to colder winters, particularly in northern India, where temperatures may drop by 1-2°C below normal.
- Furthermore, La Niña reduces the frequency of cyclonic disturbances over the Bay of Bengal, redirecting moisture-laden winds towards northern and central India.
About the El Niño Southern Oscillation (ENSO):
- About:
- ENSO is a climate pattern characterised by variations in ocean temperatures and atmospheric conditions across the central and eastern tropical Pacific Ocean.
- Phases:
- El Niño: Warmer-than-average sea surface temperatures in the central and eastern Pacific Ocean. It often leads to altered weather patterns globally, such as increased rainfall in the southern U.S. and drought in Australia.
- La Niña: Cooler-than-average sea surface temperatures in the central and eastern Pacific Ocean. It typically results in opposite weather effects compared to El Niño, such as wetter conditions in Australia and drier conditions in the southwestern U.S.
- Neutral: Neither El Niño nor La Niña conditions; sea surface temperatures and atmospheric conditions are near average.
- Cycle:
- ENSO events occur irregularly, typically every 2 to 7 years, and last for about 9 to 12 months. They can sometimes persist for longer.
What is El Nino and La Nina?
El Niño
- About:
- El Niño refers to the unusual warming of surface waters in the eastern tropical Pacific Ocean.
- It is the “warm phase” of the ENSO cycle and occurs more frequently than La Niña.
- Initially recognized by Peruvian fishermen as warm water along the coast, it was named “El Niño,” meaning “the little boy” in Spanish.
- Over time, El Niño has come to denote irregular and intense climate changes rather than just warming of coastal waters.
- Occurrence and Characteristics
- El Niño events are irregular and occur at intervals of two to seven years.
- These events are linked with the Southern Oscillation, which involves changes in air pressure over the tropical Pacific Ocean.
- During El Niño, warmer waters in the eastern tropical Pacific lead to decreased atmospheric pressure above the ocean.
- The combined phenomena of El Niño and the Southern Oscillation are referred to as the El Niño-Southern Oscillation (ENSO).
Monitoring El Niño and La Niña
- Technologies and Methods
- Data collection involves scientific buoys, which float on water and are typically bright in colour for visibility.
- These buoys measure ocean and air temperatures, currents, winds, and humidity.
- Data from these buoys is transmitted daily to researchers and forecasters worldwide.
- The Oceanic Niño Index (ONI) measures deviations from normal sea surface temperatures.
- El Niño intensity ranges from weak temperature increases (4-5°F) with moderate effects to very strong increases (14-18°F) with significant global climatic impacts.
Impact of El Niño
- General Effects
- El Niño impacts ocean temperatures, currents, coastal fisheries, and local weather from Australia to South America.
- Increased rainfall due to convection above warmer waters results in significant precipitation in South America.
- This leads to flooding and erosion.
- Conversely, El Niño causes droughts in Indonesia and Australia, threatening water supplies and agriculture.
- El Niño can reduce hurricane occurrences in the Atlantic and causes upwelling of cold, nutrient-rich water in the eastern Pacific.
Previous El Niño Events
- Notable Instances
- The 1982-83 event saw sea surface temperatures in the eastern tropical Pacific rise by 9-18°F above normal.
- The 1997-98 event, the first scientifically monitored El Niño, resulted in droughts in Indonesia, Malaysia, and the Philippines.
- Peru and California experienced severe flooding.
- The Midwest saw record-breaking warm temperatures during “the year without a winter.”
La Niña:
About:
- La Niña, meaning “The Little Girl” in Spanish, is sometimes referred to as El Viejo, anti-El Niño, or simply “a cold event.”
- It represents periods of below-average sea surface temperatures across the east-central Equatorial Pacific.
- La Niña is indicated by a sea-surface temperature decrease of more than 0.9°F over at least five successive three-month seasons.
Conditions of La Niña
- La Niña occurs when water temperatures in the Eastern Pacific become colder than usual.
- This leads to strong high pressure over the eastern equatorial Pacific.
- Lower-than-normal air pressure over the western Pacific contributes to increased rainfall.
- Rainier-than-normal conditions are observed over southeastern Africa and northern Brazil.
- Strong La Niña events can lead to catastrophic floods in northern Australia.
- Higher-than-normal pressure over the central and eastern Pacific results in decreased cloud cover and rainfall in that region.
- Drier-than-normal conditions are observed along the west coast of tropical South America, the Gulf Coast of the United States, and the pampas region of southern South America.
Impact of La Niña
Regional Effects
- Europe
- La Niña leads to milder winters in Northern Europe (e.g., the UK) and colder winters in Southern/Western Europe.
- This can result in snow in the Mediterranean region.
- North America
- La Niña results in stronger winds along the equatorial Pacific and favourable conditions for hurricanes in the Caribbean and central Atlantic.
- Increased tornado activity is observed in various US states.
- South America
- La Niña causes drought in Peru and Ecuador.
- It generally benefits the fishing industry of western South America.
- Western Pacific
- La Niña increases the potential for landfall of storms, leading to heavy floods in Australia and rising temperatures in the Western Pacific, Indian Ocean, and off the Somali coast.
La Niña in 2010
- Significant Event
- The 2010 La Niña event was linked to severe flooding in Queensland, Australia.
- Over 10,000 people were evacuated.
- The damage was estimated at over $2 billion.
Comparing El Nino, La Nina with Normal Conditions:
Latest Predictions of La Niña and Impact of Delayed Onset
- Latest Predictions of La Niña:
- The most prolonged La Niña event lasted from 2020 to 2023.
- The preceding El Niño episode occurred between June 2023 and May 2024, followed by a transition to the neutral ENSO phase.
- Current predictions indicate that initial signs of La Niña may appear by the end of September or early October 2024, with the peak expected in November and continuation through the northern hemisphere winter.
- Initial forecasts had suggested a La Niña onset around July. Prediction errors are attributed to weather models being more adept at detecting strong El Niño or La Niña phases rather than weaker ones.
Impact of Delayed Onset on the Indian Climate:
- Southwest Monsoon (June – September):
- A delayed La Niña onset does not necessarily equate to poor monsoon performance.
- For instance, the IMD predicted a 109% above-normal rainfall this monsoon season.
- However, regional disparities exist, with several states in the east and northeastern regions experiencing deficient rainfall.
- Northeast Monsoon (October – December):
- Known as the winter monsoon, it affects Tamil Nadu, coastal Andhra Pradesh, Rayalaseema, southern interior Karnataka, and Kerala.
- Although La Niña typically does not favour northeast monsoon rainfall, there have been exceptions in the past.
- Cyclogenesis:
- The north Indian Ocean basin, encompassing the Bay of Bengal and the Arabian Sea, experiences peak cyclone activity in May and November.
- La Niña years are associated with increased cyclogenesis, with storms often exhibiting above-average intensity and extended duration.
UPSC Civil Services Examination Previous Year Question (PYQ)
Prelims
Q:1 With reference to ‘Indian Ocean Dipole (IOD)’ sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct? (2017)
- IOD phenomenon is characterised by a difference in sea surface temperature between tropical Western Indian Ocean and tropical Eastern Pacific Ocean.
- An IOD phenomenon can influence an El Nino’s impact on the monsoon.
Select the correct answer using the code given below:
- 1 only
- 2 only
- Both 1 and 2
- Neither 1 nor 2
Ans: (b)
Mains
Q:1 Drought has been recognized as a disaster in view of its spatial expanse, temporal duration, slow onset and lasting effects on vulnerable sections. With a focus on the September 2010 guidelines from the National Disaster Management Authority (NDMA), discuss the mechanisms for preparedness to deal with likely El Nino and La Nina fallouts in India (2014)
Q:2 Most of the unusual climatic happenings are explained as an outcome of the El-Nino effect. Do you agree? (2014)
Source: IE
FAQs
Q: What is La Niña?
- Answer: La Niña is a climate pattern where sea surface temperatures in the Pacific Ocean are cooler than usual. This phenomenon affects weather patterns around the world, including in India.
Q: How does La Niña impact the Indian climate?
- Answer: In India, La Niña usually leads to stronger monsoon rains, which can result in above-average rainfall. While this can be beneficial for agriculture, it may also cause flooding in certain regions.
Q: Does La Niña affect winters in India?
- Answer: Yes, La Niña can make winters colder in northern parts of India. The cooler Pacific waters influence wind patterns, leading to a drop in temperatures, especially in northern states.
Q: Is La Niña beneficial for Indian agriculture?
- Answer: La Niña can be beneficial for agriculture by bringing more rain, which helps in crop irrigation. However, excessive rainfall during La Niña years may lead to floods, damaging crops and affecting farming communities.
Q: How long does La Niña last, and how often does it occur?
- Answer: La Niña typically lasts for 9 to 12 months but can extend up to two years. It occurs every 2 to 7 years and alternates with El Niño, which has opposite effects on global climate.
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