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In the equatorial Pacific Ocean, La Niña is thought to be the opposite of El Niño, which is marked by abnormally warm ocean temperatures. Together, La Niña and El Niño are the El Nino-Southern Oscillation's (ENSO) "cold" (La Niña) and "warm" (El Niño) phases. ENSO is a group of connected ocean and meteorological phenomena. Changes in air pressure are another characteristic of ENSO, in addition to abnormally warm or cool sea surface temperatures.

The accumulation of cooler-than-normal waters in the tropical Pacific, which is the region of the Pacific Ocean between the Tropics of Cancer and Capricorn, is what causes La Niña. Upwelling is the process by which this cold water rises to the surface due to unusually powerful, eastward-moving ocean currents and trade winds. The sea surface temperature can drop sharply as a result of upwelling.

During the 1988-89 La Niña period, coastal sea-surface temperatures near Ecuador and Peru decreased by almost 4 degrees Celsius (7 degrees Fahrenheit). Western South America's fishing industry typically benefits from La Niña. Cold, nutrient-rich waters rise to the top due to upwelling. Plankton, which fish and crabs eat, is a source of nutrients. The crustaceans are eaten by higher-ranking predators, such as valuable fish species like sea bass.

Unlike El Niño, which typically lasts no more than a year, La Niña occurrences can last anywhere from one to three years. Winter in the Northern Hemisphere is often when both phenomena peak.

Several tools are used by scientists to gather information regarding El Niño and La Niña. For example, the National Oceanic and Atmospheric Administration (NOAA) has a network of buoys that measure humidity, winds, currents, air temperature, and sea surface temperature. The buoys can be found in roughly 70 places, ranging from Australia to the Galapagos Islands. Every day, these buoys provide data to meteorologists and researchers.

Scientists can more precisely forecast ENSO and see its evolution and effects globally by combining buoy data with visual information they get from satellites.

A cooler-than-normal Pacific Ocean region between Indonesia and South America is known as La Niña, a phase of the El Niño Southern Oscillation (ENSO). El Niño, its opposite, is a warming of the same area. These two stages have a major impact on weather patterns and atmospheric circulation worldwide. India experiences normal or above-average rainfall during the monsoon season in La Niña years. However, the same mechanism exacerbates hurricanes across the Atlantic Ocean and produces droughts in Africa.

El Niño, on the other hand, increases rainfall in the southern United States while bringing severe summers and droughts to India. La Niña was supposed to appear by July of this year, but it hasn't. Due to this delay, the India Meteorological Department now predicts a milder winter along with the arrival of a La Niña by late 2024 or early 2025. An El Niño occurred in 2023 after this decade started with three consecutive La Niña occurrences (2020–2022), a unique phenomenon known as Triple Dip La Niña. Because rising sea and land temperatures upset the balance of the Pacific, climate change may make both La Niña and El Niño occurrences more frequent and intense. Additionally, this can intensify severe La Niña episodes, which typically cause India to have harsh winters.

WHAT IS LA NINA?

• In Spanish, it means "Little Girl." Other names for La Niña include El Viejo, anti-El Niño, or just "a cold event."

•The eastern Pacific Ocean gets colder than usual as a result of the trade winds getting stronger than usual and pushing warmer waters towards the Indonesian coast.

EMERGENCE OF LA NINA

• La Niña has only developed twice between October and December since 1950, and it often forms during the monsoon or pre-monsoon season.

• In order to forecast La Nina, the Oceanic Niño Index (ONI) compares the East-Central Tropical Pacific's three-month average sea surface temperatures to the 30-year average. An El Niño occurs when the difference between the two is 0.5º C or more and it is a La Niña when it is -0.5º C or lower. At the moment, it is at -0.3º C. For ONI readings to be considered a true La Niña or El Niño, they must surpass the criteria at least five times in a row.

IMPACT ON WEATHER PATTERN

• North America: La Niña is frequently linked to warmer, drier weather in the southern U.S. (such as the southwestern states) and colder winters in the northern U.S. and Canada.

• South America: La Niña frequently brings more rain to Brazil while causing droughts in places like Ecuador and Peru.

• Asia and Oceania: Countries like Indonesia, Australia, and portions of Southeast Asia are more likely to experience flooding and greater rainfall during La Niña.

IMPACT ON INDIA

  • Stronger monsoons are due to more rainfall in most areas.
  • A higher chance of waterlogging and flooding in several areas of the nation.
  • Lower temperatures in the winter and post-monsoon seasons.
  • The Indian Ocean is seeing more cyclones, which puts coastal regions in greater danger.
  • Potential agricultural interruptions brought on by floods, heavy rains, and postponed harvesting
  • Winter Effects: Colder Winters: Northern India experiences somewhat warmer daytime temperatures during La Niña winters, but colder nights.
  • Higher wind speeds contribute to better air quality by dispersing air pollutants.
  • Pollution may worsen if contaminants are trapped closer to the ground by a lower planetary boundary layer height (PBLH).Present Situation: Although there is a 57% chance that La Niña will form later in 2024, it has not yet materialized as anticipated.
  • Summers and Monsoons: Enhanced Monsoons: La Niña years, such as 2020–2022, have brought below-average to normal rainfall.
  • Relief from Heat: La Niña provides relief from heatwaves that occur during El Niño years by lowering the intensity of the summer.
  • El Niño Impact: El Niño causes droughts because its hotter summers frequently interfere with the monsoon season. For instance, rainfall was lower than usual in 2023, an El Niño year.

WHY IS LA NINA DELAYED IN 2024?

But in 2024, it has been abnormally delayed, with the Oceanic Niño Index (ONI) lingering at -0.3°C (the threshold for La Niña is -0.5°C or lower). Normally, La Niña arises during the pre-monsoon or monsoon season. The following would occur if La Niña formed:

  • Northern India experiences milder winters.
  • The summer of 2025 will see stronger monsoons.

CONCLUSION

Because rising sea and land temperatures upset the balance of the Pacific, climate change may make both La Niña and El Niño occurrences more frequent and intense. Therefore, if a La Niña arises now or early next year and lasts until the monsoon season, it would be a pleasant event. India would see more rain and a milder summer as a result.

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