Smartbook 7

Cold phase

A shallow thermocline in the western Pacific, an extensive warm pool pushed against the landmass of the western Pacific, and strengthened Walker cell circulation are associated with the _________ of ENSO.

El Niño

A(n) ______ occurs when warm water from the western Pacific moves eastward and replaces the cold waters off the coast of South America. This warm water limits upwelling and causes changes to the local ecosystem and weather patterns across Earth.

greater

Because the energy gradient between the poles is ______ in the winter than the summer, the change associated with ENSO are also more drastic at this time.

It is pushed downward as the surface layer of warm water is expanded.

During an El Niño, what happens to the thermocline in the eastern Pacific?

By Hadley cell circulation

How are the ENSO effects in the equatorial Pacific spread to higher latitudes?

Pressure changes in Darwin are positively correlated with air pressure changes in other parts of the world.

How are the changes in air pressure recorded in the Southern Oscillation Index (SOI) between Darwin, Australia, and Tahiti correlated with air-pressure changes in other parts of the world?

The three phases of ENSO feed moisture into the jets at different locations, mostly affecting areas to the east (the direction of airflow).

How do the changes associated with ENSO affect the subtropical and polar jets?

The conditions are bad for the fishing industry.

How does El Niño affect the fishing industry of the western coast of South America?

Trade winds blow water westward and pile it up in the western Pacific warm pool. The winds then weaken, and this pile of water flows to the east.

How does a Kelvin wave, associated with El Niño, start in the western Pacific?

-The southern and East Coast of the U.S. experience higher than average atmospheric pressures. -The air pressure changes are nearly the reverse of those during El Niño.

How does air pressure typically change in the Northern Hemisphere during the cold phase (La Niña) of ENSO?

It moves the location and changes the strength of the ascending limb of the IOD.

How does an ENSO event affect the Indian Ocean Dipole (IOD)?

The Kelvin wave brings in warm water from the western Pacific.

How does the warm water off the west coast of South America get there during an El Niño event?

3 meters per second

How fast does the Kelvin wave associated with El Niño move across the equatorial Pacific?

The IOD shares an ascending limb with the Walker cell in the Pacific.

How is the Indian Ocean Dipole (IOD) linked to ENSO events?

constantly

How often do the atmosphere and oceans interact?

- Upwelling off the coast of South America is strengthened. - Walker cell circulation strengthens over the equatorial Pacific. - The warm pool is pushed westward toward Australasia and Indonesia.

Identify conditions associated with the cold phase (La Niña) of ENSO.

-Walker cell circulation strengthens over the equatorial Pacific. -The warm pool is pushed westward toward Australasia and Indonesia. -Upwelling off the coast of South America is strengthened.

Identify conditions associated with the cold phase (La Niña) of ENSO.

- Warm air rises over the western equatorial Pacific warm pool, producing low pressure and abundant rain. - Westward displacement of surface waters drives upwelling of cold, deep water off the coast of western South America.

Identify conditions associated with the neutral phase of ENSO in the equatorial Pacific.

-Rainfall over the central Pacific is increased. -The thermocline in the western Pacific becomes shallower.

Identify conditions associated with the warm phase (El Niño) of ENSO.

Higher pressures will exist in the eastern Pacific from southern Chile to California.

If the Southern Oscillation Index is positive (higher pressure in Tahiti), which of the following will most likely occur?

The warm phase (El Nino)

If the trade winds weaken just east of the International Date Line and the pressure increases in Darwin, Australia, relative to Tahiti, what has likely just begun?

1. Easterly trade winds blow water to the west 2. Water piles up in the pacific warm pool 3. The easterly trade winds weaken 4. The mound in the warm pool starts to flow to the east

Order the steps below that take place to form a Kelvin wave associated with El Niño. (Place the first step at the top.)

1. El nino 2. Neutral 3. La Nina

Rank the phases of ENSO in terms of SST in the equatorial eastern Pacific. (Place the phase with the highest SST in the eastern Pacific at the top.

- Trade winds weaken, reducing coastal upwelling. - Descending air is pushed eastward over the equatorial parts of the Andes, reducing rainfall in Colombia and parts of the Amazon.

Select the atmospheric changes in the South American region associated with the warm phase (El Niño) of ENSO.

The conditions in the oceans are closely tied to the conditions in the atmosphere, and vice versa.

Select the statement below that best summarizes the amount of feedback between the atmosphere and the oceans.

- The Kelvin wave travels to the east. - The thermocline behind (to the west of) the Kelvin wave rises after the wave passes. - The Kelvin wave increases sea level and SST where it is.

Select the statements below that describe the effects of a Kelvin wave as it moves across the equatorial Pacific during the warm phase of ENSO.

Southern Oscillation

Sir Gilbert Walker noticed that when air pressure went up in Darwin, Australia, it went down in Tahiti (in the central Pacific) and that when it went down in Darwin, it went up in Tahiti. This linked change in air pressures is called the ______.

subtracting the air pressure at Darwin, Australia, from the air pressure measured at Tahiti

The Southern Oscillation Index (SOI) is determined by ______.

The air rises on the eastern side of the ocean, flows west, and descends over the western equatorial Indian Ocean before returning east.

The atmospheric circulation across the Indian Ocean is called the Indian Ocean Dipole. Select the best description of that circulation below.

ENSO

The linked responses of El Niño and the Southern Oscillation are known by the acronym ______

True

True or false: The warm and cold phases of ENSO can displace the jet streams from their normal paths.

The links between climatic changes in one region and climatic changes in a distant region

What are teleconnections?

Abundant rain and floods in Peru and Chile and Collapse of the fishing industry

What are the effects of El Niño in the South America region?

Warm, neutral, and cold

What are the three surface-water temperature-determined phases of ENSO in the eastern equatorial Pacific?

-There is a temporary weakening of the trade winds just east of the International Date Line at the start of the warm phase. -An increase in atmospheric pressure occurs in the westernmost Pacific relative to locations farther east in the Pacific.

What are two early lines of evidence indicating the warm phase of ENSO may have started?

El Niño and Southern Oscillation

What does ENSO stand for?

It starts to move back to the west and disperses to become less distinct.

What happens to the Kelvin wave that causes El Niño to weaken?

Warmer surface waters from the west replacing the colder water off the west coast of South America

What is El Niño?

The warm pool of water that moves across the equatorial Pacific

What is a Kelvin wave with respect to an El Niño event?

Modeling by supercomputers

What is the primary research tool used to try to predict ENSO events?

It transports the effects north and south by connecting with the east-west Walker cell circulation.

What role does Hadley cell circulation play in moving the effects of ENSO around the globe?

Wet and cool

What type of winter occurs in the southern U.S. during El Niño conditions?

- Sea-surface temperatures (SST) - Changes in atmospheric pressures - Changes in the strength of the trade winds

What types of data are collected in an effort to directly predict El Niño events?

They reoccur about once every 5 to 7 years and last 12 to 18 months.

What was been the temporal pattern of El Niño in recent decades?

- Increased rainfall occurs in the central Pacific. - Reduced rainfall occurs in the western Pacific.

Which of the following changes are likely to take place in the warm phase (El Niño) of ENSO?

-Increased rainfall occurs in the central Pacific. -Reduced rainfall occurs in the western Pacific.

Which of the following changes are likely to take place in the warm phase (El Niño) of ENSO?

ENSO events drive changes in the depth of the thermocline.

Which of the following statements best describes the link between the depth of the thermocline in the equatorial Pacific and ENSO events?

The warm phase

Which phase of ENSO is associated with colder than normal SST in the western Pacific?

In the winter, the energy gradient between the lower and higher latitudes is greater. A stronger gradient results in stronger weather patterns.

Why are the changes associated with ENSO events typically greater in the winter than in the summer?

The warm pool in the Kelvin wave starts to move back to the west, and generally disperses.

Why does El Niño eventually start to weaken?