What is ENSO, El nino, La nina, Southern Oscillation, Walker Circulation | UPSC / IAS

Summary

This video script explains the El Niño-Southern Oscillation (ENSO) phenomenon, focusing on its occurrence in the Pacific Ocean. It describes the oscillation of ocean temperatures between warm and cool states, affecting global weather patterns. The script outlines three phases: the neutral phase with typical Walker circulation, El Niño with weakened trade winds causing a warm current shift, and La Niña with strong trade winds pushing warm currents westward, leading to contrasting weather effects in different regions.

Takeaways

• 🌊 El Niño and La Niña are part of the ENSO (El Niño-Southern Oscillation) phenomenon, which mainly occurs in the southern hemisphere, particularly in the Pacific Ocean.
• 🌡 The term 'oscillation' refers to the back-and-forth fluctuation of ocean temperatures, from warm to cool and vice versa.
• 🌍 The Pacific Ocean, being the largest ocean, is the key area where these temperature fluctuations occur due to its location at the equator and the intense sun rays it receives.
• 🔄 The 'neutral phase' of ENSO is a conceptual state for understanding, where the Central Pacific Ocean is warm, and trade winds push warm water towards the western Pacific.
• 🌀 Trade winds, also known as tropical easterlies, play a crucial role in the distribution of warm water in the Pacific Ocean.
• 🌧️ The western Pacific, known as the 'western Pacific pool,' becomes warm due to trade winds, affecting the atmosphere with increased temperature and moisture, leading to cloud formation and rainfall.
• 🌀 The Walker circulation is the pattern of rising air in the West and falling in the East, which is a key part of the neutral phase of ENSO.
• 🌊 El Niño occurs when trade winds weaken, allowing the warm pool to move towards the central and eastern Pacific, disrupting the Walker circulation and causing drought in Australia and heavy rain in South America.
• 🌧️ La Niña is the opposite of El Niño, with strong trade winds pushing the warm ocean current westward, leading to heavy rains in Australia and a cooling effect in the eastern Pacific.
• 🌡 Thermocline is the term used for the rising path of water temperature from the deep ocean to the surface, which is a significant feature during La Niña.
• 🔄 The oscillation between El Niño and La Niña is a continuous process, with each phase impacting weather patterns across the globe.

Q & A

What does ENSO stand for?

ENSO stands for El Niño-Southern Oscillation, which refers to the periodic warming and cooling of the Pacific Ocean's surface temperature.

Why is the term 'oscillation' used in the context of ENSO?

The term 'oscillation' is used because it describes the back and forth movement of the ocean temperature from warm to cool and vice versa.

Which ocean is primarily affected by ENSO?

The Pacific Ocean is the primary ocean affected by ENSO, being the largest and located at the equatorial region.

What is the role of trade winds in the ENSO cycle?

Trade winds, also known as tropical easterlies, play a crucial role in the ENSO cycle by pushing the warm ocean current towards the western Pacific during the neutral phase.

What is the 'neutral phase' of ENSO?

The neutral phase is a conceptual state where no significant El Niño or La Niña conditions are present, and the Central Pacific Ocean is warm, serving as a baseline to understand the onset of ENSO phenomena.

How does the Walker circulation affect the weather patterns during the neutral phase of ENSO?

During the neutral phase, the Walker circulation causes rising air in the western Pacific, leading to cloud formation and rainfall, while sinking dry air in the eastern Pacific results in clear skies and less rainfall near the South American coast.

What happens during the El Niño phase of ENSO?

During El Niño, the trade winds weaken, allowing the warm ocean current to move towards the central and eastern Pacific, leading to a shift in weather patterns with heavy rainfall near the Peruvian coast and drought in Australia.

What is the significance of the thermocline during the La Niña phase?

In the La Niña phase, the strong trade winds push the warm surface water towards the western Pacific, causing the cold water from the deep ocean (thermocline) to rise to the surface, affecting the temperature and weather patterns.

How does La Niña impact the weather differently from El Niño?

La Niña, characterized by a cold ocean current, brings heavy rains to the western Pacific regions like Australia, Indonesia, and New Zealand, contrasting with El Niño's impact on the eastern Pacific.

What is the relationship between El Niño and La Niña in terms of their geographical locations?

El Niño and La Niña are opposite phases of ENSO, with El Niño affecting the eastern Pacific and La Niña affecting the western Pacific, oscillating back and forth between these regions.

Why is the Pacific Ocean particularly susceptible to ENSO phenomena?

The Pacific Ocean is susceptible to ENSO phenomena due to its size, location at the equator, and the presence of trade winds, which facilitate the movement of warm and cold currents.