Full Answer
What is El Nino and the Southern Oscillation?
El Nino and the Southern Oscillation (ENSO) is a climate phenomenon that occurs every two to seven years. Sir Gilbert Walker discovered “the Southern Oscillation” or large-scale changes in sea level pressure from Indonesia and the tropical Pacific Ocean. He didn’t realize that it was related to changes in the Pacific Ocean or El Niño.
What is the Southern Oscillation?
Sir Gilbert Walker discovered the “Southern Oscillation,” or large-scale changes in sea level pressure across Indonesia and the tropical Pacific. However, he did not recognize that it was linked to changes in the Pacific Ocean or El Niño.
What is El Niño and ENSO?
Further research found that El Niño is actually part of a much larger global variation in the atmosphere called ENSO (El Niño/Southern Oscillation). The Southern Oscillation refers to changes in sea level air pressure patterns in the Southern Pacific Ocean between Tahiti and Darwin, Australia.
What are the two phases of ENSO?
Though ENSO is a single climate phenomenon, it has three states, or phases, it can be in. The two opposite phases, “El Niño” and “La Niña,” require certain changes in both the ocean and the atmosphere because ENSO is a coupled climate phenomenon.
What is the timescale of a typical El Nino Southern Oscillation?
El Niño events typically occur every three to seven years and start when the trade winds blowing from the northeast, near the equator in the Northern Hemisphere, weaken. In a strong event, the winds can actually reverse and flow from the west.
How long does El Nino Southern Oscillation last?
How long does ENSO last? El Niño typically lasts 9–12 months, and La Niña typically lasts 1–3 years. Both tend to develop during March–June, reach peak intensity during December–April, and then weaken during May–July. However, prolonged El Niño episodes have lasted 2 years, and even as long as 3-4 years.
What is the El Niño Southern Oscillation cycle?
El Niño and La Niña are the warm and cool phases of a recurring climate pattern across the tropical Pacific—the El Niño-Southern Oscillation, or “ENSO” for short. The pattern shifts back and forth irregularly every two to seven years, and each phase triggers predictable disruptions of temperature, precipitation.
Does El Niño occur every 2 7 years?
Episodes of El Niño and La Niña typically last nine to 12 months, but can sometimes last for years. El Niño and La Niña events occur every two to seven years, on average, but they don't occur on a regular schedule. Generally, El Niño occurs more frequently than La Niña.
How long does El Niño last?
9-12 moñthsHow long do El Niño and La Niña typically last? El Niñ o typically lasts 9-12 moñths while La Niñ a typically lasts 1-3 years.
Is 2022 an El Niño year?
Numbers-wise, there's about a 60% chance of La Niña through the summer, ticking up a bit to the mid 60%s around 66% by October–December 2022. The second most likely outcome is ENSO-neutral conditions. El Niño is a distant third, with chances only in the low single digits through the early winter.
Why is El Niño called Southern Oscillation?
El Niño and the Southern Oscillation, also known as ENSO is a periodic fluctuation in sea surface temperature (El Niño) and the air pressure of the overlying atmosphere (Southern Oscillation) across the equatorial Pacific Ocean.
How does El Nino Southern Oscillation work?
El Niño–Southern Oscillation (ENSO) is an irregular periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean, affecting the climate of much of the tropics and subtropics. The warming phase of the sea temperature is known as El Niño and the cooling phase as La Niña.
What are the 3 stages of ENSO?
We can use surface-water temperatures in the eastern equatorial Pacific to designate conditions as one of three phases of the El Nino-Southern Oscillation (ENSO) system — neutral (or “normal”), warm (El Nino), and cold (La Nina).
What happens to the pattern of the trade winds every 3 to 7 years?
El Niño and La Niña are opposite phases of a natural climate pattern across the tropical Pacific Ocean that swings back and forth every 3-7 years on average. Together, they are called ENSO (pronounced “en-so”), which is short for El Niño-Southern Oscillation.
How long does La Niña last?
"Normally, La Niñas dissolve at the end of summer or early autumn," Dr Ridder said. "This one is dissolving very slowly. The forecast at the moment is that it will be May or June before it will be back to neutral conditions.
Are we in a La Niña year?
The current La Niña started around September 2020 and has been mild-to-moderate most of the time since then. As of April 2022, it intensified, leading to a cold snap over the eastern equatorial Pacific Ocean not seen at that time of year since 1950.
What are the 3 stages of ENSO?
We can use surface-water temperatures in the eastern equatorial Pacific to designate conditions as one of three phases of the El Nino-Southern Oscillation (ENSO) system — neutral (or “normal”), warm (El Nino), and cold (La Nina).
What is the difference between El Niño and Southern Oscillation?
El Niño and the Southern Oscillation, also known as ENSO is a periodic fluctuation in sea surface temperature (El Niño) and the air pressure of the overlying atmosphere (Southern Oscillation) across the equatorial Pacific Ocean.
How often does ENSO occur?
every 3-7 yearsEl Niño and La Niña are opposite phases of a natural climate pattern across the tropical Pacific Ocean that swings back and forth every 3-7 years on average. Together, they are called ENSO (pronounced “en-so”), which is short for El Niño-Southern Oscillation.
Are we in an El Niño year?
An El Nino is currently more likely in late 2022 and especially during the next winter season than an extended La Nina. So it's time we look at how they actually differ from each other, both in the Ocean and in the Atmosphere.
What is El Niño-Southern Oscillation?
El Niño-Southern Oscillation is a climate pattern in the Pacific Ocean that has two phases: El Niño and La Niña. In a normal year, in the Pacific Ocean, the trade winds blow westward along the Equator and push warm surface waters near Australia and Indonesia.
What are we looking at?
The plot tracks the conditions in the Pacific Ocean, showing how El Niño-like or La Niña-like the Pacific Ocean is both right now and in the past. When the value of the time series is positive (red shading), El Niño conditions are present, and when the value is negative (blue shading), La Niña conditions are present.
Why do we care?
El Niño affect fisheries, especially in South America where warm, nutrient-poor waters disrupt fishing. Also, both El Niño and La Niña events bring severe weather events. In the Southwestern United States El Niño brings rain, but in Asia and Australia flooding is usually associated with La Nina.
When were nio 1 and nio 2 created?
These regions were created in the early 1980s. Since then, continued research has led to modifications of these original regions. The original Niño 1 and Niño 2 are now combined and is called Niño 1+2.
What is SOI in weather?
The SOI is a mathematical way of smoothing the daily fluctuations in air pressure between Tahiti and Darwin and standardizing the information. The added bonus in using the SOI is weather records are more than 100 years long which gives us over a century of ENSO history. Location of El Niño monitoring zones.
What is the name of the ocean that changes the sea level air pressure patterns?
The Southern Oscillation refers to changes in sea level air pressure patterns in the Southern Pacific Ocean between Tahiti and Darwin, Australia.
What are long timescale events?
Typically, long time-scale events are often associated with changes in atmospheric circulations that encompass vast areas. At times, these persistent circulations occur simultaneously over seemingly unrelated, parts of the hemisphere, and result in abnormal weather, temperature and rainfall patterns worldwide.
Is the air pressure higher in Darwin or Tahiti?
During El Niño conditions, the average air pressure is higher in Darwin than in Tahiti. Therefore, the change in air pressures in the South Pacific and water temperature in the East Pacific Ocean, 8,000 miles (13,000 km) away, are related.
What is the Southern Oscillation Index?
The Southern Oscillation Index (SOI) is based on the pressure data from Tahiti and Darwin, which is available back to 1866. In 1923, Sir Gilbert Thomas Walker first described the large-scale circulation which accounted for the Southern Oscillation.
Is the Walker Circulation stronger than normal?
If the trade winds are stronger than normal, cool water may reach into the western Pacific. In such an event, the Walker Circulation is stronger than normal. Where El Niño describes events with a weaker than normal circulation, a stronger circulation is in many ways its opposite.
What is the Southern Oscillation?
What is the El Niño Southern Oscillation? More conveniently known as ENSO, it is the planet’s largest source of natural climate variability on interannual time scales.
Which ocean is linked to the Southern Oscillation?
Bjerknes: Linking the Pacific Ocean and the Southern Oscillation
What is the name of the loop that Bjerknes called?
Bjerknes called this atmospheric circulation loop the Walker Circulation, in honor of Gilbert Walker. Changes in the strength and position of the Walker Circulation explained fluctuations in Walker’s Southern Oscillation, and thus Bjerknes linked the Pacific Ocean with the Southern Oscillation.
How did ENSO begin?
Scientific understanding of ENSO began somewhat by chance with meteorological observations thousands of miles from the Pacific. Today, thanks to the existence of these very same teleconnections, our understanding of the current state and likely evolution of ENSO can be used as a tool to forecast distant climate conditions and inform decision making, several weeks or even months in advance.
What is the process of wind blowing from the east to the west?
Here, the air is heated, picks up moisture and rises, forming deep thunderstorms as the water vapor condenses. Once the air reaches the top of the troposphere, it spreads outwards back towards the east Pacific, where it cools and sinks back down over the colder water (Figure 2). Bjerknes called this atmospheric circulation loop the Walker Circulation, in honor of Gilbert Walker. Changes in the strength and position of the Walker Circulation explained fluctuations in Walker’s Southern Oscillation, and thus Bjerknes linked the Pacific Ocean with the Southern Oscillation.
Who developed the regression equations for the Asian monsoon?
These links can be formalized statistically, and in the 1920s, mathematician Gilbert Walker was tasked with using them to predict fluctuations in the Asian monsoon. To do this, Walker developed regression equations between Indian rainfall and other remote surface observations, such as Himalayan snowfall accumulation. Walker also came up with an index describing the long-ranging fluctuations in surface pressure that had been observed by Blanford and Todd, which he termed the “Southern Oscillation”, hence the Southern Oscillation Index (SOI).
Is the sea surface cooler in the east or west Pacific?
Bjerknes started with a simple but important observation, that on average, sea surface temperatures (SSTs) in the tropical east Pacific are much cooler than SSTs in the tropical west Pacific (Figure 1).
Overview
Diversity
The traditional ENSO (El Niño Southern Oscillation), also called Eastern Pacific (EP) ENSO, involves temperature anomalies in the eastern Pacific. However, in the 1990s and 2000s, nontraditional ENSO conditions were observed, in which the usual place of the temperature anomaly (Niño 1 and 2) is not affected, but an anomaly arises in the central Pacific (Niño 3.4). The phenomenon is called Central Pacific (CP) ENSO, "dateline" ENSO (because the anomaly arises n…
Outline
The El Niño–Southern Oscillation is a single climate phenomenon that periodically fluctuates between three phases: Neutral, La Niña or El Niño. La Niña and El Niño are opposite phases which require certain changes to take place in both the ocean and the atmosphere before an event is declared.
Normally the northward flowing Humboldt Current brings relatively cold water from the Southern …
Walker circulation
The Walker circulation is caused by the pressure gradient force that results from a high pressure system over the eastern Pacific Ocean, and a low pressure system over Indonesia. The Walker circulations of the tropical Indian, Pacific, and Atlantic basins result in westerly surface winds in northern summer in the first basin and easterly winds in the second and third basins. As a result, the tempe…
Sea surface temperature oscillation
Within the National Oceanic and Atmospheric Administration in the United States, sea surface temperatures in the Niño 3.4 region, which stretches from the 120th to 170th meridians west longitude astride the equator five degrees of latitude on either side, are monitored. This region is approximately 3,000 kilometres (1,900 mi) to the southeast of Hawaii. The most recent three-mont…
Southern Oscillation
The Southern Oscillation is the atmospheric component of El Niño. This component is an oscillation in surface air pressure between the tropical eastern and the western Pacific Ocean waters. The strength of the Southern Oscillation is measured by the Southern Oscillation Index (SOI). The SOI is computed from fluctuations in the surface air pressure difference between Tahiti (in the Pacific…
Madden–Julian oscillation
The Madden–Julian oscillation, or (MJO), is the largest element of the intraseasonal (30- to 90-day) variability in the tropical atmosphere, and was discovered by Roland Madden and Paul Julian of the National Center for Atmospheric Research (NCAR) in 1971. It is a large-scale coupling between atmospheric circulation and tropical deep convection. Rather than being a stan…
Impacts
Developing countries dependent upon agriculture and fishing, particularly those bordering the Pacific Ocean, are the most affected by ENSO. The effects of El Niño in South America are direct and strong. An El Niño is associated with warm and very wet weather months in April–October along the coasts of northern Peru and Ecuador, causing major flooding whenever the event is strong or extreme. …