El niño and la niña

What is the El Niño Southern Oscillation?

The term used to describe changes in weather patterns in the Pacific Ocean.

What are the usual weather conditions in the Pacific Ocean in a non- El Niño year?

• Strong trade winds blow from the Americas westwards towards Indonesia.

• These winds become a hot, wet air mass which creates a low pressure system at the surface. This draws more air in from high pressure systems around Ecuador.

What happens under the ocean surface in a non- El Niño year?

• West flowing trade winds move with warm surface water.

• A colder counter- current flows eastwards and upwells when it reaches South America to bring nutrients to the surface.

What happens to the weather patterns during an El Niño year?

The weather conditions reverse and western South America receives warm/wet weather while Indonesia and Australia sit under prolonged drought due to high pressure.

How long can an El Niño last for?

20 months

What are two scientific theories at to why an El Niño happens?

• Tropical storms can upset the usual trade wind balance.

• The cycles are part of a natural feedback loop to ensure no part of the ocean becomes too warm.

How does el nino affect Australia?

• The Murray-Darling basin in New South Wales experiences 28% lower rainfall in El Nino years

• This impacts agriculture and the economy (wine yields can drop by up to 40% in el nino years)

How does el nino affect peru?

• The Peruvian fishing industry struggles as waters are too warm for plankton and fish.

• 1997-98 el nino caused mass flooding due to more meltwater descending from the Andes.

Which areas are the worst affected by el nino?

Out of all the countries affected, poorer nations that rely on the primary sector such as Peru are the worst affected.