El Niño and La Niña are opposite phases of the El Niño-Southern Oscillation (ENSO) cycle. El Niño involves unusually warm waters in the eastern Pacific, while La Niña features unusually cold waters. These phenomena impact weather worldwide by affecting wind and rain patterns. During El Niño, the western U.S. tends to be wetter and cooler, while Australia and Indonesia experience drought. La Niña has opposite effects, with wetter conditions in Australia and Indonesia and drier weather in the western U.S. Scientists monitor these cycles using ocean buoys and satellites to improve predictions of their development and impacts.

1. El Niño & La Niña
PowerPoint Presentation Prepared By:
Clarence Marollano & Princess Jarme

2. EL NIÑO-SOUTHERN OSCILLATION (ENSO) CYCLE.
 El Niño and La Niña are opposite phases of what is known as the El
Niño-Southern Oscillation (ENSO) cycle.
 The ENSO cycle is a scientific term that describes the fluctuations in
temperature between the ocean and atmosphere in the east-central
Equatorial Pacific (approximately between the International Date Line
and 120 degrees West).
 La Niña is sometimes referred to as the cold phase of ENSO and El
Niño as the warm phase of ENSO. These deviations from normal surface
temperatures can have large-scale impacts not only on ocean processes,
but also on global

3.  El Niño and La Niña episodes typically last nine to 12 months, but
some prolonged events may last for years. They often begin to form
between June and August, reach peak strength between December and
April, and then decay between May and July of the following year. While
their periodicity can be quite irregular, El Niño and La Niña events occur
about every three to five years. Typically, El Niño occurs more frequently
than La Niña.

4. What is El Niño?
• El Niño means The Little Boy, or Christ Child in Spanish.
• El Niño was originally recognized by fishermen off the
coast of South America in the 1600s, with the appearance
of unusually warm water in the Pacific Ocean. The name
was chosen based on the time of year (around December)
during which these warm waters events tended to occur.
• The term El Niño refers to the large-scale ocean-
atmosphere climate interaction linked to a periodic
warming in sea surface temperatures across the central
and east-central Equatorial Pacific.

5. • Typical El Niño effects are likely to develop over North
America during the upcoming winter season. Those include
warmer-than-average temperatures over western and
central Canada, and over the western and northern United
States. Wetter-than-average conditions are likely over
portions of the U.S. Gulf Coast and Florida, while drier-than-
average conditions can be expected in the Ohio Valley and
the Pacific Northwest.

6. El Niño, warmer than average waters in the Eastern
equatorial Pacific (shown in orange on the map), affects
weather around the world.

7. The First Signs of an El Niño:
• Rise in air pressure in the Indian Ocean, Indonesia, and
Australia.
• A fall in air pressure over Tahiti and the rest of central and
eastern Pacific Ocean.
• The trade winds in the South Pacific weakened or headed east
• Warm air rises in Peru
• Warm water spreads from the West Pacific and the Indian
Ocean to the East Pacific. It takes the rain with it, causing
rainfall in normally dry areas and drought in normally wet
areas.

8. El Nino is a climate pattern that describes the unusual warming of surface
waters along the tropical west coast of South America. This diagram illustrates
the eastward movement of winds across the Pacific in red.

9. The Effects of El Niño:
• Wet winters over south-eastern United States
• Drought in Indonesia and Australia, and other places that are
typically wet
• Flood in South America in areas that are typically dry
• Wildfires and mudslides
• Warmer weather in the upper Midwest states and Canada

10. El Nino events
prevent the process
of upwelling—the
movement of cold,
nutrient-rich water
to the surface—off
the coast of Peru,
Ecuador, and Chile.
This can have a
devastating impact
on local economies.

11. El Nino events often result in unusual and destructive weather patterns. The
normally arid climate of the tropical South American coast, for instance (here,
in Chile) may experience floods and landslides during El Nino events.

12. El Nino events can also impact the western Pacific Ocean. Typhoon Winnie,
above, hit Taiwan and China during a powerful El Nino event in 1997. Typhoon
Winnie killed more than 200 people and caused more than $1 billion in
damages.

13. Australia is often plagued by drought during strong El Nino events. Here, Lake
Alexandrina, a large lake in southern Australia, is almost dried up.

14. How Well Can We Predict El Niño?
• Satellite readings from buoys strategically set
in the Pacific Ocean
• Complex computer models

15. What is La Niña?
• La Niña means The Little Girl in Spanish.
• La Niña is also sometimes called El Viejo, anti-El Niño, or
simply “a cold event”.
• La Niña episodes represent periods of below-average sea
surface temperatures across the east-central Equatorial
Pacific. Global climate La Niña impacts tend to be opposite
those of El Niño impacts. In the tropics, ocean
temperature variations in La Niña also tend to be opposite
those of El Niño.
• During a La Niña year, winter temperatures are warmer
than normal in the Southeast and cooler than normal in
the Northwest

16. La Niña is caused by a build-up of cooler-than-normal waters in the tropical Pacific, the
area of the Pacific Ocean between the Tropic of Cancer and the Tropic of Capricorn.
Unusually strong, eastward-moving trade winds and ocean currents bring this cold
water to the surface, a process known as upwelling.

17. The First Signs of a La Niña:
The first signs of an emerging La Niña event are often observed in the
ocean. The Bureau of Meteorology monitors and reports on a range
of ENSO indicators, including:
• Short-term bursts of tropical rainfall activity
• Water temperatures at the sea surface and at depth
• Ocean heat content – measuring the amount of energy stored in
the ocean
• The Southern Oscillation Index
• Atmospheric air pressure
• Cloudiness – measuring the amount of cloud in tropical regions
• The strength of the trade winds and winds higher in the
atmosphere ocean currents

18. The weather pattern known as La Nina brings warmer-than-normal sea-surface temperatures (in red) to the southern
Pacific Ocean around northern Australia, New Guinea, and the islands of Indonesia. The cooler sea-surface temperatures
of La Nina (in blue) occur in the southern Pacific off the coast of South America.

19. The Effects of La Niña:
• Rain clouds form as a result of the uplift of warm, moist air.
• Monsoon seasons will be more intense in a La Nina year.
• Western equatorial portions of South America may be
in drought conditions.
• In the United States, Washington and Oregon may see
increased precipitation.
• Portions of California, Nevada, and Colorado may see drier
conditions.

20. A group of scouts uses a disassembled cardboard box as protection against a
heavy rainstorm in Semarang, Java, Indonesia. La Nina events often bring
wetter-than-normal weather to Indonesia, northern Australia, and Malaysia.

21. How can we detect La Niña?
• The National Oceanic and Atmospheric Administration
(NOAA), for instance, operates a network of buoys which
measure sea-surface temperature, air temperature, currents,
winds, and humidity. The buoys are located in about 70
locations, from the Galapagos Islands to Australia. These
buoys transmit data to researchers and meteorologists every
day. Using buoy data in conjunction with visual information
they receive from satellites, scientists are able to more
accurately predict ENSO and visualize its development and
impact around the globe.

22. El Niño vs. La Niña
El Niño
• Usually warm ocean
temperatures in eastern
Pacific
• Usually more intense effect
than La Niña
• Summers in Omaha tends to
be wetter and cooler
• Causes drier weather on
West Pacific seaboards and
wetter, humid weather in
East Pacific
La Niña
• Usually cold ocean
temperatures in eastern
Pacific
• Usually follows El Niño but
not always
• Summers in Omaha tends to
be drier and warmer
• Causes wetter weather on
West Pacific seaboards and
drier weather in East Pacific

23. El Niño vs. La Niña
El Niño
• Warmer winters in the
upper Midwest states and
Canada
• Wet winters over south-
eastern United States
La Niña
• Colder winters in the upper
Midwest states and Canada
• Dry winters over south-
eastern United States