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The Sydney Opera House is seen as a dust storm blankets the city - Source: Reuters -
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A dust storm swept across eastern Australia and blanketed
Sydney, disrupting transport, placing health authorities on alert
for widespread respiratory illness and stripping thousands of
tonnes of topsoil off Australia's main farmlands.
Following are answers to questions about the storm:
What caused the dust storm?
During winter in Australia low pressure storms are generated in the
Indian and Southern Oceans, whipping up huge seas and creating
severe cold fronts which sweep across southern and eastern
Australia.
A severe thunderstorm with 100 km per hour plus winds formed in South Australia state on Monday and began whipping up dust from drought-hit outback lands.
As vegetation gets dried off the topsoil is loosened, and it
easily blows away. As the dust storm travelled into the eastern
seaboard state of New South Wales, one of the worst hit by drought,
it grew in size and by Wednesday morning was affecting most of NSW,
the fifth biggest state or territory representing 10 percent of the
island continent, and had descended on Sydney like a thick
blanket.
Is the dust storm linked to climate change?
Weather scientists are reluctant to directly link climate change
with extreme weather events such as storms and droughts, saying
these fluctuate according to atmospheric conditions, but green
groups link the two in their calls for action to fight climate
change.
Dust storms in Australia, the world's driest inhabited continent
with a vast desert-like outback interior, are not uncommon. Central
and eastern Australia is a major global source of atmospheric dust,
say weather experts.
But dust storms are usually restricted to the inland of
Australia. Occasionally, during widespread drought they can affect
coastal areas. Australia is battling one of its worst droughts and
weather officials say an El Nino is slowly developing in the
Pacific which will mean drier conditions for Australia's eastern
states.
Before the Sydney dust storm, one of the most spectacular storms
swept across Melbourne in February 1983, late in the severe El Nino
drought of 1982/83. The extended dry period of the 1930s and 1940s
generated many severe dust storms, culminating in the summer of
1944/45 when on several occasions dust in Adelaide was so thick
that street lighting had to be turned on.
Satellite images showed a 2002 dust storm, about 1,500 km long
by 400 km wide and 2.5 km high, stretching across New South Wales
and Queensland states.
What is the economic and environmental impact of dust
storms?
While dust storms may cause temporary disruptions to towns and
cities, by far the worst effect is the stripping of topsoil from
Australia's farmlands. In the late 1970s and early 1980s severe
drought in Australia saw dust storms strip millions of dollars
worth of topsoil, causing massive crop and stock losses, according
to the country's Emergency Management Authority.
Crop analysts say the current dust storm is unlikely to have an immediate impact on wheat crops which are already struggling with dry conditions. Harvesting starts next month in NSW, the country's second largest grain producing state.
Australian Crop Forecasters estimates the NSW wheat crop will be
down by about one million tonnes to around 6.5 million
tonnes.
Will there be more dust storms?
Australian weather officials are warning of another severe storm to
sweep across the southern and eastern parts of the country on
Thursday and Friday.
Australia's main farmlands are located in the eastern part of the country. The next storm could again whip up a dust storm, cause damage with gale-force winds and send temperatures plummeting and dump snow on Australia's alpine region.
If El Nino weather conditions continue in the western Pacific then Australia's dry conditions and then more dust storms can be expected, but whether they remain confined to inland or outback regions or sweep across farmlands and reach more populated centres remains unknown.
