1. El Nino-Southern Oscillation
ENSO
El Nino-Southern Oscillation

2. ENSO El Nino-Southern Oscillation in equatorial Pacific 5-7 year cycle
El Nino = warmer surface waters
La Nina = cooler surface waters
Changes in the walker cell during ENSO. Source:
El Niño: Warmer winters across the northern
USGulf states cooler and wetter
California can be wetter or drier
Pacific salmon and other fisheries disrupted
Fewer hurricanes in the Atlantic
La Niña:
La Niña has equally dramatic, often opposite effects on the US

3. Signs of El Nino Changes in air pressure at sea surface
Trade Winds weaken in the South Pacific
Warm air rises over Peru in South America
Drought conditions persist in western Pacific
This slide shows dry and wet areas around the world during El Nino.

4. Signs of La Nina Opposite of El Nino
Increased Hurricane activity in Atlantic
Cold, wet NW N. America
Increase upwelling offshore from Peru
This slide shows dry and wet areas around the world during La Nina.

5. Hadley Cells control the Trade winds
This flow of circulation forms air cells calledHadley Cells which generate the earth’s major air circulation masses and related wind systems (See Figure 8 from Lutgens and Tarbuck, 2007). These air movement systems are also affected by the rotation of the earth which bends and changes their direction (coriolis force). The circulation cells that most affect this part of the world form the Trade Winds. In the northern hemisphere the Trade Winds begin about 30° north latitude and blow in a northeasterly direction toward the lower equatorial pressure. In the southern hemisphere the Trade Winds begin about 30° south latitude and blow in a southeasterly direction toward the lower equatorial pressure. Where the winds meet near the equator, the air is of course heated, the pressure lowered, and if it is over water gets filled with moisture to rise again and continue the ongoing cell dynamics.

6. Coriolis Force “Apparent” force due to the rotation of the Earth
N. Hemisphere - deflection to the right
S. Hemisphere - deflection to the left
The rotation of the Earth causes an interesting phenomena on free moving objects on the Earth. Objects in the Northern Hemisphere are deflected to the right, while objects in the Southern Hemisphere are deflected to the left. The coriolis effect, thus tries to force winds to shift towards the right or left. The coriolis effect can at times cause winds to blow back up the pressure gradient.

7. Some Impacts from El Nino
Indonesia
Drought
Southwest US
FLOODING
Images of some regional impacts from El Nino.

8. Some Impacts from El Nino
Colder temps in Florida cause manatees to congregate near warm water outflows (left). El Nino causes colder winters in Europe due to decreased heat transfer of the Gulf Stream (right).