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.

Outlines

00:00

🌊 Understanding ENSO: El Nino and Southern Oscillation

This paragraph introduces the El Nino-Southern Oscillation (ENSO) phenomenon, explaining that 'El Nino' refers to the warm phase of the Pacific Ocean's surface temperature oscillations, predominantly occurring in the southern hemisphere. The term 'oscillation' indicates a back-and-forth movement, in this case, of the ocean's temperature between warm and cool phases. The focus is on the Pacific Ocean, the largest and most affected by these temperature changes due to its location at the equator and the intense sun exposure it receives. The paragraph sets the stage for a deeper exploration of ENSO by breaking it down into three phases: neutral, El Nino, and La Nina, starting with the neutral phase where the Central Pacific Ocean is warm, influenced by trade winds that push warm water towards the western Pacific, creating a cycle known as Walker circulation.

05:02

🌍 El Nino Phase: Warm Currents and Global Impacts

The second paragraph delves into the El Nino phase of ENSO, characterized by a weakening of the trade winds, allowing the warm pool of water in the western Pacific to shift towards the central and eastern Pacific. This movement signifies the oscillation referred to in the phenomenon's name. The displacement of the cold water by the warm current results in the upwelling of deep, cold water, altering weather patterns globally. The El Nino phase disrupts the Walker circulation, leading to droughts in Australia and heavy rainfall and flooding on the American continent, particularly around the Peruvian coast. The paragraph emphasizes the significant climatic effects of El Nino, urging viewers to associate the term with these weather changes.

🌧️ La Nina Phase: The Cold Counterpart to El Nino

The final paragraph discusses the La Nina phase, which is the cold phase of ENSO. Similar to the neutral phase, La Nina is marked by strong trade winds that push the warm surface current westward, allowing cold water from the deep ocean to rise to the surface, a process known as upwelling. This phase is characterized by a thermocline, the boundary between the warm surface water and the colder water below. The effect of La Nina is pronounced in the western Pacific regions, such as Australia, Indonesia, and New Zealand, where it brings heavy rains, contrasting with the droughts experienced during El Nino. The paragraph concludes by reinforcing the oscillating nature of ENSO, with El Nino and La Nina representing the warm and cold phases, respectively, that alternate across the Pacific Ocean.

Keywords

💡El Nino

El Nino refers to a climate pattern characterized by unusually warm ocean temperatures in the Equatorial Pacific. It is a significant component of the ENSO (El Nino-Southern Oscillation) cycle and has global impacts on weather patterns. In the video, El Nino is described as a phase where the warm ocean current moves towards the central and eastern Pacific, causing shifts in rainfall patterns and potentially leading to droughts or floods.

💡Southern Oscillation

Southern Oscillation is the atmospheric component of the ENSO cycle, which involves fluctuations in atmospheric pressure between the eastern and western Pacific. It is closely related to El Nino, as changes in wind patterns (trade winds) contribute to the oscillation between warm and cool phases in the ocean. The term is used in the script to explain the 'O' in ENSO, emphasizing the back-and-forth movement of atmospheric conditions.

💡Pacific Ocean

The Pacific Ocean is the largest and deepest ocean on Earth, playing a central role in the ENSO cycle. In the video, it is highlighted as the 'pool' of water that warms up due to the equatorial sun and influences global weather through the movement of warm and cold currents. The script describes how the Pacific Ocean's temperature oscillations are crucial to understanding El Nino and La Nina events.

💡Trade Winds

Trade Winds are steady, easterly winds that blow from the southeast toward the northwest in the tropics. They are pivotal in the ENSO cycle, as they influence the movement of warm ocean currents. In the script, the Trade Winds are described as pushing the warm water towards the western Pacific during the neutral phase, and their weakening during El Nino allows the warm water to shift eastward.

💡Walker Circulation

Walker Circulation is a large-scale atmospheric circulation pattern that involves the rising of warm, moist air over the warm ocean waters of the western Pacific and the sinking of dry air over the cooler waters of the eastern Pacific. The video script explains how this circulation pattern is disrupted during El Nino, leading to changes in rainfall distribution.

💡Thermocline

Thermocline refers to a transition layer between the warmer mixed surface waters and the colder deep waters in the ocean. In the context of the video, the thermocline is mentioned when explaining how during La Nina, the trade winds push the warm surface water westward, allowing cold water from the deep ocean to rise to the surface in the eastern Pacific.

💡La Nina

La Nina is the cold phase of the ENSO cycle, characterized by cooler-than-average sea surface temperatures in the central and eastern Pacific. The video script contrasts La Nina with El Nino, describing it as a phase where strong trade winds push the warm water westward, causing the upwelling of cold water in the eastern Pacific and affecting weather patterns, particularly increasing rainfall in Australia and the western Pacific islands.

💡Convection

Convection is the process by which heat is transferred in fluids (like air or water) due to the movement of mass resulting from temperature differences. In the video, convection is explained as the process that leads to cloud formation and rainfall when warm air rises and cools at the top of the troposphere, particularly in the western Pacific during the neutral phase of ENSO.

💡Troposphere

The troposphere is the lowest layer of Earth's atmosphere, where weather occurs and where the majority of air and water vapor reside. The video script mentions the troposphere in the context of how warm air rises and cools at its top, leading to the drying of air and the formation of descending dry air currents over the eastern Pacific during El Nino.

💡Neutral Phase

The neutral phase in the ENSO cycle is a period when neither El Nino nor La Nina conditions are present, and the climate patterns are relatively stable. The video script describes the neutral phase as a starting point for understanding the oscillation between El Nino and La Nina, with the central Pacific Ocean being warm and the trade winds pushing warm water towards the western Pacific.

💡Oscillation

Oscillation, in the context of the video, refers to the back-and-forth movement or fluctuation between different states, specifically the warm and cool phases of the Pacific Ocean's surface temperature. It is a key concept in understanding the dynamic nature of the ENSO cycle, as the script illustrates the oscillation between El Nino's warm phase and La Nina's cool phase.

Highlights

El Nino and Southern Oscillation (ENSO) is a climate phenomenon primarily occurring in the Southern Hemisphere.

The term 'oscillation' implies a back and forth movement, in this case, of ocean temperatures.

ENSO involves the oscillation of ocean temperatures between warm and cool in the Pacific Ocean.

The Pacific Ocean, being the largest and located at the equator, plays a central role in ENSO.

The neutral phase of ENSO is a theoretical baseline for understanding the cycle.

Trade winds, blowing from east to west, push warm water towards the western Pacific.

The western Pacific, known as the pool, is warmed by the trade winds and solar radiation.

Warm ocean currents affect the atmosphere, leading to convection and cloud formation.

Walker circulation is the pattern of rising air in the West and falling in the East.

El Nino phase is characterized by weak trade winds allowing the warm pool to move eastward.

During El Nino, the eastern Pacific experiences heavy rain and flooding due to the warm current.

La Nina is the opposite phase of El Nino, with strong trade winds pushing warm water westward.

La Nina results in a cold ocean current, affecting regions like Australia, Indonesia, and New Zealand with heavy rains.

Thermocline is the term for the rising path of water temperature from the deep ocean to the surface.

ENSO's oscillation is a continuous process with El Nino and La Nina phases alternating.

ENSO has significant global impacts on weather patterns and climate conditions.

Understanding ENSO is crucial for predicting climate changes and their effects on ecosystems and agriculture.

Transcripts

in this video we are going to learn

about Enzo II and ESCO if you break it

Ian stands for El Nino and s o stands

for Southern Oscillation because Enzo

phenomena mostly occurs at this southern

hemisphere just right below the equator

and when you look at the term

oscillation it gives us a hint that

something oscillates from one place to

another or back and forth if you want

you can pause the video and think about

what could be that thing well it's the

temperature that we are talking about

and not just any temperature ocean

temperature it is the ocean temperature

that oscillates back and forth from warm

temperature to cool temperature and

vice-versa now the next question that

should be in your mind is which ocean

are we talking about I'll give you a

hint it's the largest one Pacific Ocean

you see Pacific Ocean is this large pool

of water that exists on the western side

of the American continent and eastern

side of the Asian and Australian

continent this large pool of water gets

intensely warm due to the fact that it

exists right at the equator and we all

know that the equatorial region received

great amount of sun rays all throughout

the year so far we have learned what and

where ENSO takes place now it's time to

know how it all happens to understand

how ENSO occurs we will need to break it

into three phases that's how it will

make sense and step by step the concept

will get clearer the first phase is

neutral phase actually there is no such

thing as a neutral phase when it comes

to any of nature's phenomena you see

nature has a constant ongoing cycle that

has never stopped but for our own

understanding we will have to create a

neutral state where we can see how a

particular thing starts and goes on so

the first phase among the three phases

is the neutral phase in this phase this

Central Pacific Ocean is warm now let's

bring in the trade winds

trade winds are these wind that blows in

the tropical region from eastern side to

the western side they are also known as

tropical

easterlies so as we know that the

equator receives great amount of sun

rays and that's what warms the Pacific

Ocean the trade winds pushes the warm

ocean car

towards the Asian side because trade

winds blow from east to west and that

makes the western Pacific Ocean warm you

know the region around New Zealand

Australia and Indonesia this region is

called the western Pacific pool here the

ocean temperature is warm the warm ocean

current affects the surrounding

atmosphere by increasing the temperature

as well as the moisture content and we

know that warm air rises high into the

atmosphere it is through the convection

process and that's how clouds are formed

and then it rains the warm air then

travels east towards eastern Pacific

Ocean

you know the region near South America

especially countries like Ecuador and

Peru the warmer air when it goes up it

reaches the end of troposphere and if

you know the top of the troposphere is

cold when warm air meets cool air slowly

it loses its moisture content and the

air becomes dry the dry air travels

towards the eastern Pacific side and

comes down over the Peruvian coastal

region making the region cold this

pattern of rising air in the West and

falling in the East continues and it is

known as Walker circulation so this was

the neutral phase I hope you understood

this cycle it's plain and simple now

comes the second phase it's called El

Nino so in the neutral phase we saw that

the trade winds played an important role

in pushing the warm ocean current

towards the western Pacific now in this

phase the trade winds a weak yes there

are few months in a year when the trade

winds a week when the trade winds are

weak the warm ocean current do not get

any kind of push so what happens is the

warm pool of ocean water at the western

Pacific slowly moves towards the central

and eastern side of the Pacific Ocean so

this is where the oscillation term comes

in you see the warm ocean current is

replacing the cold ocean current that

exists in the central and eastern

Pacific

when I say replace what I mean is that

the cold water is dense and it settles

down in deep ocean and warm water goes

up and takes over the surface of the

ocean ok I hope you're understanding

when this warm ocean current moves

everything that is associated with it

like the convection process then the

formation of rain cloud everything moves

along with this warm ocean current what

you will notice now is that the Walker

circulation that we saw in the neutral

phase that one big looping pattern it's

now breaking into two parts just look at

this loop as a result the ocean

temperature near Australia is cool and

there is no rain though the inland parts

of Australia witness a severe drought

condition but on the other hand near the

Peruvian coast the warm pool of ocean

current brings heavy rain flood to the

American continent so whenever you hear

the word El Nino immediately think of

warm ocean current and the third phase

is La Nina this is similar to the

neutral phase in this phase the trade

winds are strong since trade winds blow

from east to west

hence it pushes the warm ocean current

from the eastern Pacific toward stay

west in Pacific now imagine this cold

water is dense and it settles down in

deep ocean so that means the temperature

of the ocean surface is warm now if the

trade wind pushes the warm surface ocean

current towards the western Pacific the

cold water from the deep ocean

immediately comes up at the surface

there's a word given to it it's called

thermocline thermocline is the rising

path of water temperature and the rest

of the process is same we saw that in

the neutral phase western Pacific region

of Australia Indonesia New Zealand gets

heavy rains strong the effect of La Nina

is more on these countries than El Nino

so El Nino is a warm ocean current and

La Nina is a cold ocean current remember

that if El Nino is at the eastern

Pacific then La Nina will be at the

opposite region that is western Pacific

and it oscillates back and forth