CLIMATEDOGS

The Climatedogs are a representation of some of the climate processes that drive rainfall variability across Australia. Different Climatedogs affect different parts of the country. There are four major Climatedogs (Enso, Indy, Ridgy and Sam), and two smaller Climatedogs (Eastie and Mojo) who affect weather on a smaller scale. It’s important to remember that the Climatedogs work together to drive the climate, so we need to look at the combined effect of all of the indicators to get a good picture of what we expect to happen in the future.

THE ROUNDUP – INTRODUCING THE CLIMATEDOGS

TRANSCRIPT

Meet the Climatedogs. They represent the climate processes that drive the ranifall variability across Australia. These working dogs love rounding up our rainfall.

From a farmer’s perspective, when they’re behaving, they bring moisture from the oceans and allow it to fall as rain – hopefully delivering the right amount at the right time. But they don’t always work how we’d like them to, and can sometimes scatter the mob, effectively chasing rainfall away from Australia. These dogs often work as a team, helping one another to bring about our wetter and drier seasons.

Over recent decades, some of these dogs have started to change their behaviour, contributing to the variability and changing weather patterns that many farmers have noticed. While we can’t control what these climate dogs are up to, there are new and improved tools that can assist farmers to keep an eye on the pack, helping to improve our understanding of seasonal forecasts and manage climate risks.

INTRODUCING ENSO – The El Niño Southern Oscillation

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The El Niño Southern Oscillation, or Enso, has a big influence on Australia’s climate and seasonal variability.

In a normal, or neutral, year, the Pacific Ocean trade winds blow from east to west, pushing moist air towards Australia. This moist tropical air is a big source of rain across many parts of Australia. But Enso’s behaviour can vary from year to year.

During La Niña, Enso chases greater amounts of moist tropical air across Australia. Many La Niña years have seen higher winter and spring rainfall across large parts of Australia. And in northern Australia, the first rains of the wet season tend to be earlier during La Niña years, along with an increased chance of floods and tropical cyclones.

During El Niño, Enso changes its mind and drives warm moist air away from Australia and towards South America instead. El Niño years have often resulted in a drier winter and spring for eastern Australia, as well as an increased chance of frost and heatwave events. Up north, El Niño can bring a later start to the wet season rains, with typically fewer tropical cyclones and floods.

Enso often teams up with the other climatedogs to affect our seasonal rainfall. Climatologists closely follow Enso’s behaviour, looking at ocean temperatures, the SOI, and cloud and wind patterns to work out where it might chase that moisture next. So Enso is definitely an important dog to keep your eye on.

INTRODUCING INDY – The Indian Ocean Dipole

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This is the Indian Ocean Dipole, also known as Indy, who influences south-east and central Australia’s rainfall, mainly in spring. Indy likes to herd moisture from the warm north-east Indian Ocean across to south-eastern Australia. When this moist air meets up with southern weather systems, it can deliver significant rainfall. Some years, the north-eastern Indian Ocean is cooler than normal, meaning less evaporation and Indy can’t deliver as much moisture, usually meaning a drier spring in the centre and south-east.

Historically Indy often likes to team up with Climatedog Enso, with both being a significant source of rainmaking moisture. In recent years, scientists have noticed that much of the Indian Ocean has been getting warmer, and that’s why they are investigating Indy’s behaviour, so we can better understand this Climatedog and improve our rainfall forecasts in the future.

INTRODUCING RIDGY – The Sub-tropical Ridge

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This is Ridgy or, as scientists like to call him, the Sub-tropical Ridge. Ridgy is one of the major drivers that shapes southern Australia’s weather. So let’s look at how he does it.

As warm air rises in the tropics, moves south, then cools and falls, large areas of high pressure are created. This band of high pressure – in this case, Ridgy – is great at blocking rain-bearing fronts. From November through until April, Ridgy chases away cold fronts around southern Australia for days or even weeks at a time. When winter sets in, Ridgy heads north and cold fronts find it much easier to reach southern Australia and deliver their rain, until Ridgy returns again next November.

Ridgy travels north and south every year, but in recent decades he’s been getting more effective at chasing away cold fronts from parts of southern Australia, meaning more dry weather and later autumn breaks. The Bureau of Meteorology has observed that Ridgy’s increasing strength is related to the rising global average temperature. but the scientists are continuing to investigate how this climate dog might change his behaviour in the future.

INTRODUCING SAM – The Southern Annular Mode

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Meet Sam. Sam herds cold fronts up from the Southern Ocean, a significant source of rain for much of southern Australia. If we take a look at the Southern Ocean, we can see westerly winds roaring around Antarctica, throwing out cold fronts of stormy wet weather. The strength and position of these winds is known as the Southern Annular Mode, or Sam.

Sam is an unreliable climate dog, often changing behaviour over a matter of weeks. This can affect southern Australia’s rainfall in winter, and even parts of eastern and northern Australia’s rainfall in summer. When Sam is tied up, strong winds are pulled south towards Antarctica and there is a reduction in the number and strength of cold fronts that reach southern Australia, reducing winter rainfall.

When Sam is let off the leash, this can drive westerly winds further north, increasing the chance of cold fronts and rainfall across the southern states. But in summer, Sam acts a bit differently. If Sam is sitting further south, it can actually coax more moisture and summer rain over parts of eastern & northern Australia.

Sam’s behaviour is complicated, and is linked to what the other Climatedogs are up to. However, over recent decades Sam has been tied up more often, resulting in fewer cold fronts and less cool-season rainfall for parts of southern Australia. Scientists are watching this climate dog closely, hoping to tease out how it may impact our weather and seasonal climate variability down the track.

INTRODUCING EASTIE East Coast Low-Pressure Systems

TRANSCRIPT

This is Eastie, better known as the East Coast Low. Eastie represents the deep low-pressure systems that are an important climate feature along the south-east coast of Australia. These deep low-pressure systems can be caused by upper-atmosphere disturbances, decaying cyclones, existing low-pressure conditions or in the wake of passing fronts.

Scientists have found that Eastie tends to have a mind of his own and can be quite hard to predict. This energetic little dog can be triggered into action overnight causing strong winds, big surf, heavy rains and lots of rough weather. Eastie can appear all year round but typically prefers the seasons of autumn and winter. Even one-off events can dominate a region’s annual rainfall tally, explaining a lot of the seasonal variability east of the Great Dividing Range.

Eastie usually cares little about what the larger climate dogs are up to; however, scientists have noticed that Eastie can be a bit timid when Ridgy, with his high pressure, is around. Scientists continue to look into Eastie’s behaviour.

INTRODUCING MOJO – The Madden-Julian Oscillation

TRANSCRIPT

This is the Madden­‐Julian Oscillation or, as we like to call him, MOJO. He can have a big influence on Australia’s weather and climate, especially during the warmest months of the year.

Mojo runs eastward moving a pulse of cloud and rainfall close to the equator and travels around the earth every thirty to sixty days. Mojo sends a wave of weather across the Indian Ocean which can create cyclones and bring widespread rain events through parts of Australia. Scientists track these rain making waves providing updates on the intensity and timing of the next wave.

Mojo mainly affects northern Australia, but can influence rain events further south, especially if one of Mojo’s moisture waves feeds into a timely weather event down south. Mojo’s behaviour is often unpredictable, with periods of moderate to strong activity followed by periods of little or no activity, but this dog is well worth keeping an eye on.