Excerpt
The dusty blanket that wrapped itself around Sydney this morning pushed air pollution levels to 1500 times their normal levels - the highest on record, a climate scientist says.
Sydneysiders woke to a red dawn this morning as a thick dust storm caused havoc with transport and raised health fears.
The size of the dust cloud surprised weather experts, who say it has covered half of NSW.
Dr John Leys, principal research scientist with the NSW Department of Climate Change and Water, said initial estimates showed the dust plume stretched 600 kilometers along the NSW coast from Sydney to the Queensland border this morning, dumping up to 75,000 tonnes of dust per hour into the Tasman Sea.
"It's traveled about 1500 kilometers to get to Sydney," Dr Leys said.
Chris Eiser, manager of atmospheric science at the department, said measurements taken in Sydney today showed the highest level of particle concentration on record.
A normal day would see around 10 micrograms of particles per cubic metre of air and a bushfire might generate 500 micrograms.
Today, levels soared to 15,400 micrograms per cubic metre of air at one location.
"During a dust storm, that’s when we get our highest levels historically and this is the highest we’ve measured in Sydney," Mr Eiser said.
Bureau of Meteorology regional director Barry Hanstrum said it was unusual to see such a wide area covered by dust.
"It's a very unusual event to see a blanket of thick dust like this cover such a large area of NSW," Mr Hanstrum said.
"We see [dust storms] fairly regularly but what we don't see is dust this thick make it across to the coast.
"More than half the state at midday today is under this cloud and the dust is starting to spread north and east and is likely to affect parts of Queensland as well in the next 24 hours."
The haze would not disappear until the low pressure system over Sydney - which brought the dusty winds - moved out to sea, most likely in the evening.
"We should see an improvement in the Sydney area later today but it will be slow, and overnight and into tomorrow we'll see a return to more typical conditions for this time of year," Mr Hanstrum said.
"As the low pressure system moves away, then it will continue to transport the dust out to sea.
"And as winds become more south-westerly, it will bring air from further south and that area wasn't affected by dust storms."
Josh Fisher, meteorologist from weatherzone.com.au, said there was a "ridge of high pressure ... edging east" that was also causing winds to ease.
Most dust would be carried out to sea by the low pressure system, but some would settle to the ground, Mr Hanstrum said.
He also described how the dust cloud this morning had morphed from crimson red about dawn, through orange and yellow and into a paler grey late this morning.
"With the low sun angle first thing in the morning, it's a bit like the angle of the sun at sunset ... you see a reddish tinge in the sky.
"As it got higher in the sky the colour of the dust cloud changed. Now currently it's a grey pall that's over the city and that's because the sun is pretty well directly overhead."
The dusty cloak would keep temperatures in the low 20s today, Mr Fisher said.
"The dust haze will work to keep temperatures lower and, as it clears, the winds are going to turn more south-westerly, bringing in cooler air and some cloud cover with that.
"We'll see temperatures struggle to reach 20 degrees today."
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