El Niño, La Niña, ENSO, IOD: what do they mean for Australia?
What goes on in the Indian and Pacific oceans has a direct impact on the weather we experience in Australia. Each phase or cycle of these weather patterns bring with them different conditions – from more rain to warmer temperatures.
By understanding what’s in store, you can take steps to protect your home or business.
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There’s often news about El Niño and La Niña, the El Niño Southern Oscillation (ENSO), the Indian Ocean Dipoles (IOD), and the impact they have on our weather here in Australia.
But what does it all mean?
Sometimes it can feel as if you need a degree in meteorology to really understand it – so we’ve broken it down, so you’ll soon know your IODs from your ENSOs.
Why is it important to understand the ENSO cycle, El Niño, La Niña and IOD?
Essentially they all affect the weather we experience, not just in Australia, but across the world. The ENSO cycle in particular is the climate pattern responsible for extreme weather events. So, by brushing up on our meteorological knowledge, we can understand the likelihood of these events – for example, floods or droughts – and prepare for whatever they might bring.
What is an ENSO cycle?
The ENSO cycle is a natural climate pattern that is determined by the winds, clouds and water temperature in the central and eastern tropical Pacific Ocean.
It has three ‘states’ – neutral, El Niño and La Niña,1 all of which mean different things for the weather we experience, particularly in the eastern, northern and more central areas of Australia. It generally takes around four years to swing from El Niño to La Niña and back again.2
What happens during the neutral phase of an ENSO cycle?
During the neutral phase, trade winds – winds that blow east to west in the tropical Pacific – warm up the water in the western Pacific. While over in the east, those same trade winds create cooler water off the coast of South America.
The heat rising to the north of Australia and then descending near South America causes a cycle called the ‘Walker Circulation”. We’re in this state for more than half the time – and during this time we’re more likely to see ‘normal’ weather here in Australia, although droughts and floods are still possible.3
What is La Niña?
In a La Niña phase, those trade winds get even stronger. The water north of Australia gets warmer, while the water by South America gets cooler, meaning there’s an even greater temperature difference. Once this phase begins, it’s ‘locked in’ for at least 12 months.4
What is the weather impact of La Niña in Australia?
With these higher water temperatures, we get more cloud, evaporation, and rain here in Australia – meaning lower daytime temperatures and an increased chance of flooding.5
What is El Niño?
El Niño is the opposite of La Niña. During El Niño, trade winds reduce or even reverse, meaning those warmer waters drift back towards South America. The change in temperature pattern results in the water to the east becoming warmer – and evaporation, cloud and rain moving away from Australia.6
What is the weather impact of El Niño on Australia?
With a drier climate comes increased changes of drought, higher temperatures. Less rainfall, a longer frost season and fewer tropical cyclones.7
What is the Indian Ocean Dipole (IOD)?
The IOD is another climate pattern that affects the weather in Australia. It describes the difference in sea surface temperature between the eastern and western parts of the Indian Ocean – from the area around Indonesia to the east coast of Africa.
Essentially, it’s like ENSO, but in the Indian Ocean.8 The IOD has three phases – neutral, positive and negative.
How does a positive IOD impact weather in Australia?
During a positive IOD phase – where the sea surface temperature is higher in the western Indian Ocean, we’ll see fewer clouds in Australia’s northwest, and less rainfall in southern Australia and towards the Top End.
How does a negative IOD impact weather in Australia?
A negative IOD occurs when the water in the western Indian Ocean is cooler than the eastern Indian Ocean; winds become westerly, bringing more cloud and rain, which can cause flooding, particularly in the northwest and southern areas of the country, as well as the Top End.9
When does a neutral Indian Ocean Dipole occur?
The neutral IOD phase occurs when there is no significant difference in temperature between the eastern and western Indian Ocean.
Are ENSO and IOD cycles linked?
It is thought that the two are related – typically a positive IOD will be associated with El Niño, while a negative IOD is associated with La Niña.10
Why is it important to know what the weather has in store?
Knowledge of what’s going to happen from a weather perspective is always valuable. After all, if you know there’s an increased likelihood of a flood or drought you can prepare your home and business to better deal with it.
For example, if Australia is forecast to experience drier conditions and you’re in a bushfire prone area, then you might want to prepare your home and business for bushfires. If there’s a higher risk of flooding and storms, then, of course, it makes sense to prepare your home and business accordingly, too.
Remember to plan ahead
Arming yourself with as much information as possible before an event occurs is essential. Make sure you download the BOM app as well as state and territory government apps to alert you to weather-related dangers.
Plus, it’s always a good time to check your home insurance or business insurance is up to date and covers your property, possessions and business adequately.
If you’d like talk about your insurance needs, contact your broker or call our team on 133 723.
1 What is the El Niño–Southern Oscillation (ENSO) in a nutshell? – NOAA Climate.gov
2 About Australian Climate – Bureau of Meterology
3 About Australian Climate – Bureau of Meterology
4 About Australian Climate – Bureau of Meterology
5 About Australian Climate – Bureau of Meterology
6 What is El Niño and what might it mean for Australia – Bureau of Meterology
7 What is El Niño and what might it mean for Australia – Bureau of Meterology
8 Indian Ocean Dipole – Bureau of Meterology
9 Indian Ocean Dipole – Bureau of Meterology
10 Indian Ocean Dipole – Bureau of Meterology
