Weather

Worksheet: El Nino / La Nina

Sheet 3: Southern Oscillation

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In the Basics section you have seen the normal condition in the pacific and also the deviations under El Niño conditions. (see text El Nino and Worksheets 3, 4, 5 in the basics section). In the section more - text El Nino and SOI you get more information. After having gone through those materials, you should be able to answer the following questions.

The seasonal variation of the pressure patterns is called the Southern Oscillation.
Whenever this happens - every 3-6 years - the whole system in the pacific plays up.

Think of the texts and animations/maps before.

Can you answer the following questions?

1) Under El Niño conditions the sea level is ...

a) higher off New Zealand.
b) higher off Australia.
c) higher off Indonesia.
d) higher off South America.

2) Under El Niño conditions the trade winds ...

a) flow moderately from West to East.
b) flow moderately from East to West.
c) flow strongly from West to East.
d) flow strongly from East to West.

3) Under El Niño conditions the trade winds ...

a) bring no rain to South America.
b) bring no rain to Indonesia and Australia.
c) bring rain to Australia.
d) bring rain to Europe.

4) Under El Niño conditions the trade winds ...

a) bring drought to Chile and Peru.
b) bring drought to the Easter Islands.
c) bring drought to the equatorial region of Southeast-Asia.
d) bring drought to the Andes.

5) Under El Niño conditions ...

a) the water of the pacific becomes warmer because the cold Humboldt stream is not pushed in a western direction.
b) the water of the pacific becomes colder because the cold Humboldt stream is not pushed in a western direction.
c) the water of the pacific becomes warmer because the warm Humboldt stream is not pushed in a western direction.
d) the water of the pacific becomes warmer because the cold Humboldt stream is not pushed in an eastern direction.

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And how does El Niño affect the whole Pacific region?

Look at the maps showing the precitpiation and the deviation from the normal year.

Name the regions/countries which have more rain than usual and those which have less.
Drought conditions often result in bush fires, poor harvests, and economic problems.

Precipitation total deviation from
January-March 1998 (mm) normal (factor 100)

Drought in South East Asia under El Niño conditions. author: Bildungszentrum Markdorf'Projektgruppe ENSO', data from NOAA climate prediction center, source: http://www.enso.info/enso.html#normal

The whole phenomenon is called ENSO which is short for "El Niño" and "Southern Oscillation".

In short

ENSO conditions are irregular weather conditions which occur frequently and mean world wide weather disturbances:
Either drought and no rain (where there should have been rain)
or too much rain (where no rain is expected).

About this page:

- Author: Dr. Schrettenbrunner - University of Nürnberg - Germany
- scientific reviewing:
- educational reviewing: Dr. Yvonne Schleicher , Julia Heres
- last update: 08.09.03