Rare weather event over Antarctica driving Australia’s hot, dry outlook
A uncommon occasion that came about 30 kilometres above the South Pole final week is predicted to impression upon Australia’s rainfall outlook.
- Sudden stratospheric warming is far more frequent within the northern hemisphere
- Meteorologists are warning it’ll lead to greater temperatures and a lower in rainfall
- It’s not believed to be brought on by international warming however is a ‘pure phenomenon’
The higher environment above Antarctica warmed by as a lot as 40 levels Celsius in the middle of a number of days — and it’s persevering with to heat.
This uncommon phenomenon, often called sudden stratospheric warming (SSW), might deepen one of many worst droughts in Australian historical past.
The Bureau of Meteorology’s Harry Hendon warned of dry climate forward.
“We are going to sometimes see circumstances throughout most of Australia, however primarily concentrated within the jap a part of Australia, turn out to be hotter and drier by means of spring and into early summer time,” Dr Hendon mentioned.
SSW is uncommon within the southern hemisphere with just one main occasion ever recognized, in 2002 — one in all Australia’s driest years on file.
2002 had record low rainfall, influenced by a sudden stratospheric warming. (Supplied: Bureau of Meteorology)
Dr Hendon mentioned related, much less intense stratospheric warmings had been linked to different dry years in Australia.
“Previously 30 years we in all probability have had 5 – 6 occurrences that did not fairly qualify as a sudden stratospheric warming,” he mentioned.
“We checked out what occurred over that interval and we’re fairly assured that we are going to see a rise in temperatures and a lower in rainfall in central-eastern Australia within the following months.”
Not local weather change however ‘pure phenomenon’
SSW is just not regarded as brought on by international warming.
“We view SSW as a pure, internally-generated phenomena,” Dr Hendon mentioned.
“It simply occurs to be very uncommon within the southern hemisphere.”
It’s far more frequent within the northern hemisphere the place SSWs are related to chilly climate.
Final February, the ‘beast from the east’ storm that covered much of Europe in snow was triggered by an SSW over the North Pole.
Antarctic temperatures have an effect on Australia
Sudden stratospheric warming over Antarctica causes westerly winds south of Australia to trace additional north, a sample meteorologists confer with as a ‘damaging SAM’.
In spring and summer time, this damaging SAM sample brings hotter, drier air into southern Queensland and New South Wales.
In summer, a negative SAM is associated with a decreased chance of rain in central-eastern Australia. (Supplied: Bureau of Meteorology)
“Sadly, these are areas already in drought,” mentioned a lead creator of the BOM’s spring local weather outlook, Andrew Watkins.
Dr Watkins mentioned cooler than regular water within the Indian Ocean, a phenomenon meteorologists name a ‘optimistic IOD’, has led to a scarcity of moisture drifting over the continent.
“This has definitely been a giant consider why winter has been so dry in just about all of Australia,” he mentioned.
“On high of that, we’ve the probability of extended intervals of damaging SAM, which additionally brings drier circumstances to New South Wales and southern Queensland.
“So it’s kind of of a double whammy in these areas.”
A positive IOD is associated with a reduced chance of rain. (Supplied: Bureau of Meteorology)
Dr Watkins mentioned the impression of the SSW could also be felt in Australia by means of to the top of the yr.
“These sudden stratospheric warming occasions and the patterns that we see from them can go from September [to] October, typically persisting by means of to January,” he mentioned.
Dr Hendon mentioned he was gratified the Bureau of Meteorology’s pc fashions have been in a position to predict the occasion.
“In 2002 we did not even find out about it till after it occurred, and we did not know if we might ever be capable of predict it,” he mentioned.
“It is thrilling for us now that we’ve predictive functionality that we did not have in 2002.”