Follow these instructions to create an El Niño effect in your kitchen, and learn about global weather patterns.
Warning: This activity involves hot water and an electrical appliance. Make sure there's an adult around to supervise.
Australia's climate sometimes swings from dry conditions one year to floods the next. This is due to a phenomenon around the Pacific Ocean called the Southern Oscillation. The most well known extreme of the Southern Oscillation is the drought-causing El Niño (el-neen-yo).
The El Niño effect
El Niño is the Spanish word for the boy-child, a reference to the baby Jesus. The name was given because an El Niño event is characterised by the appearance of warm ocean currents off the coast of South America at Christmas time (the time of the birth of the boy-child Jesus).
But what does this have to do with Australia? In normal years the cool water over in the eastern Pacific near South America is blown west, and is warmed by the tropical sun along the way. When this warm water reaches the coast of Australia it warms the air, making it rise and creating cumulo-nimbus clouds that bring summer rain.
In an El Niño year, the circulation across the Pacific weakens, so the upwelling of cool waters is reduced, the warm water stops before it gets to Australia and we have a drought.
The effects of El Niño reach right around the globe. When we have droughts, large areas of Indonesia, India and Southern Africa also experience dry conditions, Peru gets floods, and parts of North America get very warm.
Build your own El Niño
To do this activity you will need the following:
What to do
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Half-fill a large glass pyrex baking dish or plastic tupperware container with very hot water. Add red food colouring to the water (taking care not to scald yourself!).
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Next, in a separate container, mix up some very cold water with blue food colouring. Using a funnel, carefully add this cold water to the bottom of the baking dish. Notice how the hot and cold water do not mix. This represents an El Niño situation, where the warm water on top prevents the cooler water from rising to the surface.
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To set up the conditions normally experienced, direct a stream of air from a hair dryer or fan over the surface of the water. (Warning: keep the electrical appliance well away from the water itself. If the hair dryer should come into contact with the water, you should turn it off at the power point. Do not reach in to fish it out).
What's happening
As the air blows over the surface of the water, the hot water will move to the other end of the container. The cold water will rise to the surface near the fan, replacing the hot water. This represents the usual winds that drive the warm water west to Australia. Turn off the fan, and look at the slope between the hot and cold water. Does the water return to El Niño conditions now that the wind has stopped?
Of course, the ocean's water is not exactly half hot, half cold. The warm layer is really a thin surface layer. While this model helps you understand the processes at work, it doesn't give an accurate representation of El Niño. For scientists to understand what's happening in real life, they have to closely monitor the oceans and the atmosphere. While their understanding is increasing, there's still a lot to be learned.
by Simon Torok
For more hands-on activities, join CSIRO's Double Helix Science Club.
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