Unit 9: Southern Oscillation

Question 1

Southern Oscillation:

Answer 1

A changing pattern of reversing surface air pressure between the Eastern and Western tropical pacific regions.

Question 2

Normal Tropical Pacific conditions:

Answer 2

• Trade winds blow WEST across pacific, pushing warm surface water westward from the coasts of South America to Australia
• As the water most WEST it heats up from exposure to Solar Radiation
• Difference in heating between the waters in the WEST and EAST causes a thermocline to form.
• Upwelling occurs in Eastern pacific to replace waters (Nutrient rich, good fishing)
• Warm water in Western pacific, increases evaporation, therefore increased cloud formation, then rainfall.
• Dry air that falls from Western pacific to EAstern results in little rainfall in Eastern tropical pacific.

Question 3

Tropical Pacific conditions during El Nino:

Answer 3

• Trade winds weaken, and sometimes even reversew allowing warmer waters from the Western pacific to flow toward the East.
• Therefore sea level flattens.
• Warm water builds up off the coast of South America, increasing the temperature of the water.
• Upwelling decreases, causing death of fish.
• Heavy rainfall in peru, as warm waters evaporate and cause formation of clouds,.
• Drought over Indonesia and Australia, as trade winds no longer bring moist air over which contributes to cloud formation.

Question 4

Tropical Pacific conditions during La Nina:

Answer 4

• Trade winds strengthen, blowing even more warm water to the Western Pacific.
• Causes increased upwelling in Eastern Pacific and lower surface sea temperatures.