What is the El Nino phenomenon?

El Nino and La Nina are opposing phases of the El Nino-Southern Oscillation (ENSO) cycle. The ENSO is a periodic climatic trend that involves temperature fluctuations in the eastern and central tropical Pacific Oceans, as well as changes in upper and lower-level wind patterns, sea level pressure, and tropical rainfall patterns over the Pacific basin. The warm phase of ENSO is typically referred to as El Nino, whereas the cold phase is referred to as La Nina. These deviations from average surface temperatures have the potential to have a substantial impact on global weather and climate conditions. 

This article will help you to understand what the La Nina and El Nino phenomena are and how they affect Indian weather.


El Nino Meaning

In Spanish, El Nino means "small boy" or "Christ child". As it was initially seen by South American fishermen in the early 17th century, the phenomenon was given this name. Seas tended to become warm in the Pacific Ocean around December, which is why the name was picked. El Nino is a large-scale ocean-atmosphere climatic interaction associated with a recurrent increase of sea surface temperatures in the central and east-central Equatorial Pacific. It is linked to high pressure in the western Pacific. The El Nino effect has a negative influence on the Indian monsoons and, as a result, agriculture in India.

According to the work of Sir Gilbert Walker, climate scientists discovered that El Nino and the Southern Oscillation occur at the same time in the 1930s. A variation in air pressure over the tropical Pacific Ocean is known as the Southern Oscillation. The air pressure over the ocean lowers when coastal waters in the eastern tropical Pacific get warmer (El Nino). El Nino-Southern Oscillation is the name given to these two interconnected occurrences by climatologists (ENSO). The words El Nio and ENSO are now used interchangeably by most subject experts.


El Nino's Impact on India

The pressure distribution in a typical monsoon year (without El Nino) is as follows.

  • The pressure along Peru's coast in South America is higher than in the region bordering northern Australia and South East Asia. 

  • As the Indian Ocean is warmer than the surrounding oceans, it has lower pressure. As a result, moisture-laden winds blow from the western Pacific to the Indian Ocean. 

  • As the pressure on India's landmass is lower than that on the Indian Ocean, moisture-laden winds go farther from the ocean to the lands. The monsoons are disturbed if this typical pressure distribution is disrupted for any cause.

El Nino causes the chilly surface water off the Peruvian coast to warm. The regular trade winds are lost or alter their direction when the ocean is warm. As a result, moisture-laden winds from the western Pacific are steered towards Peru's coast (the region near northern Australia and South East Asia). It creates significant rainfall in Peru, during the El Nino, depriving the Indian subcontinent of its typical monsoon rains. The greater the temperature and pressure differential, the greater is the rainfall deficit in India.


La Nina Meaning

In Spanish, La Nina means "small girl", and it is also known as El Viejo, or "cold event". In the Eastern Pacific, the water temperature drops below average. As a result, a powerful high-pressure system has formed over the eastern equatorial Pacific. Low pressure is now present in the Western Pacific and off the coast of Asia. La Nina causes drought in Peru and Ecuador, major floods in Australia, high temperatures in the Western Pacific, Indian Ocean, and off the coast of Somalia, and abundant monsoon rains in India. La Nina conditions are really advantageous to the Indian monsoon. El Nino and La Nina weather patterns occur every 4–5 years on average. El Nino is more common than La Nina. Typically, the episodes last nine to twelve months.


Effects of El Nino and La Nina on Indian Climate

El Nino generates warm weather across the Indian subcontinent in the winter and dry conditions and a deficient monsoon in the summer. In contrast, La Nina causes a better-than-normal monsoon in India. During the El Nino years of 2002 and 2009, India had little rainfall, although the monsoon was typical during the El Nino years of 1994 and 1997. It signifies that India faced droughts during the monsoon for nearly half of the year due to El Nino in the summer. El Nino will harm crops such as paddy, maize, groundnut, guar, castor, tur, moong, and bajra. 


El Nino: Measuring the Effects

Scientists, governments, and non-governmental organizations (NGOs) use a variety of technology, including scientific buoys, to collect data on the El Nino effect. A buoy is a floating object that serves as a navigational aid or warning signal for ships in the middle of the ocean. They are usually brightly coloured (fluorescent). Temperatures, currents, winds, and humidity are all measured by these buoys. The buoys provide data to academics and forecasters all across the world on a regular basis, allowing scientists to more correctly anticipate El Nino and visualize its evolution and influence around the planet.

The Oceanic Nino Index (ONI) is a tool for determining how much sea surface temperatures have deviated from normal. The major tool for determining, assessing, and forecasting each El Nino event is the Oceanic Nino Index, which is a measure of the departure from normal sea surface temperature in the east-central Pacific Ocean. El Nino occurrences range in severity from mild temperature rises (about 4-5° F) with relatively little local effects on weather and climate to extremely severe increases (14-18° F) linked to global climate change.

FAQs on El Nino

1. What Causes El Nino and La Nina?

El Nio is the term used to describe the above-average sea-surface temperatures that occur on a regular basis in the east-central equatorial Pacific. It reflects the ENSO cycle's warm phase. The periodic decrease of sea-surface temperatures throughout the east-central equatorial Pacific is referred to as La Nia. It reflects the ENSO cycle's chilly phase. 


El Nino and La Nina are naturally occurring phenomena caused by interactions between the ocean surface and the atmosphere across the tropical Pacific. Changes in ocean surface temperatures have an influence on tropical rain patterns and atmospheric winds over the Pacific Ocean, which in turn have an impact on ocean temperatures and currents. These two linked patterns of tropical rainfall induce changes in weather patterns across the world.

2. What is the Average Duration of El Nino and La Nina?

El Nino is a natural phenomenon in which ocean temperatures rise, particularly in portions of the Pacific Ocean. On the other hand, the opposite phenomenon of this is termed as La Nina which causes ocean water to 'chill' in regions of the Pacific Ocean. El Nino lasts 9-12 months on average, whereas La Nina lasts 1-3 years. They both began to develop in March-June, peaking in intensity in December-April and then waning in May-July. On the other hand, prolonged El Nino episodes have lasted anywhere from two to four years. Due to the highest intensity during the winter months, weather patterns are also most observable in the winter.

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