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Australia gets new advanced weather radar,
courtesy of the Bureau of Meteorology . . .
Bringing
you much
more than
pretty
pictures!
I first noticed this giant “golf ball” last
year, sitting high on its “tee”, right next to the
Terrey Hills golf driving range in Sydney’s north.
“Surely,” I thought, “that’s not just an advert for the
driving range . . .”
No it’s not (although I bet they are very grateful!) –
it’s much more interesting than that – it’s the latest in
the Bureau of Meteorology weather radar upgrades!
And the best part: you can view its images via the ’net.
by Ross Tester
www.siliconchip.com.au
www.siliconchip.com.au
siliconchip.com.au
JJanuary
anuary 2010 21
2010 21
A typical PC “radar” screen showing approaching rainfall.
You can add a lot more map features if you wish.
W
eather forecasting around
Australia has become even
more accurate and precise
with the opening of several new highresolution Doppler weather radar
installations.
With the newest at Laverton (Vic),
Mt Stapylton (Brisbane, Qld) and now
at Terrey Hills in Sydney’s north, each
has already proved their $4 million
price tags money well spent.
You can become your own weather
forecaster by following the weather
radar images on the Bureau of Meteorology’s website.
The images from the newest technology weather radars cover the last half
hour with screens six minutes apart.
Older radars have images 10 minutes
apart.
There’s always a lag of up to about
eight minutes – you can look out the
window and see that it’s raining where
you are when the screen tells you that
the rain is still approaching (and vice
versa). That’s mainly because of the
incredible amount of computer “number crunching” then the upload times
to the net.
You can also show the whole of Australia with clouds and
rain interpolated from all other radar sites.
You get the choice of 64, 128 and
256km range, plus a 512km “composite” interpolated from other radars.
You can also enable or disable a variety of map features, such as locations,
roads, topography, etc.
Rainfall is colour-coded by intensity
– my experience is that anything yellow or above is getting rather heavy!
You can log on to the Bureau’s website (www.bom.gov.au) and follow the
prompts – the Terrey Hills radar images, for example, are at www.bom.gov.
au/products/IDR714.loop.shtml#skip.
But there’s a lot more than just radar
images to look at. The Bureau has a vast
array of tools to help the average person
understand what the images represent
and how to use them.
The Terrey Hills radar
Completed in April last year and
commissioned after extensive testing
on September 9, it is the fifth of six
new high resolution weather radars
to come online around the country
thanks to the Federal Government’s
$62.2 million radar upgrade project. In
fact, the Government has extended the
program with another four high resolution weather radars to be installed as
part of the upgrade program.
As far as Sydney is concerned, the
Terrey Hills installation effectively
replaces the Appin (south of Sydney)
weather radar which has been operating since 1992.
As well has having double the resolution of the Appin radar, Terrey Hills
also has Doppler capability, which
allows the display of wind flows associated with weather systems as well
as rainfall intensity.
Another problem for the Appin radar was/is that is considered too high
above sea level to properly detect lowlevel rainfall over the Sydney area (as
you can see by comparing the images
from Appin and Terrey Hills at the
same time).
The Appin Radar will continue to
operate in the short term. The Bureau
is currently examining sites to the
south of Sydney for a planned new
Wollongong radar.
On-going operational benefits of the
Terrey Hills weather radar will include:
• Improved short-term forecasts and
The Moving Storm: Monday, November 30 2009
22 Silicon Chip
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Left: it’s not rain – how those on
the ground wished it was – these
radar images from Melbourne
(Laverton) at 09.00 UTC (8pm
EDT) on 7 February last year,
at the height of the Victorian
bushfires, where smoke was
dense enough to show up.
Right: the colour-code located
underneath each map/image
refers to the rainfall intensite.
Here’s the key – and while it’s
not absolutely accurate, it’s
not too bad, either. I’ve only
seen dark brown once – and
that was a day that Sydney
would rather forget!
warnings of severe weather, including hail, damaging winds and
tornadoes
• Improved radar-derived rainfall
rates for use in flood warning applications
• Improved short-term forecasts of
rainfall
• Enhanced tracking of the movement
and strength of wind changes such
as southerly busters, cold fronts and
sea breezes.
Because the newest weather radars
are Doppler, they can be used to measure speed – of wind, of storm fronts,
and so on. Weather radars don’t reflect
off clouds (the droplets are too small)
but they reflect off the raindrops those
clouds produce.
Unfortunately, they also sometimes
reflect off birds and insects, aircraft and
even bats taking to they sky at dusk!
Radar close to the coast may also reflect
off shipping.
The newest site
The radar site at Terrey Hills
(33.701°S, 151.210°E) is 195m above
sea level and is approximately 18km
north of the Sydney CBD. The radar
covers more than a quarter of Australia’s population.
Based on detecting echoes at a height
of 3000m, the radar has an unobstructed view to the north, south and east.
However, the rough topography of
the Great Dividing Range slightly compromises the radar’s view to the west.
Even so, high-level (ie upper-atmosphere storm) range extends west to
Mudgee and Bathurst, as far north as
Bulahdelah and Scone (in the Hunter
Valley), and south to Goulburn and
Ulladulla (NSW south coast).
An examination of the coverage map
will show that these limits overlap the
coverage area of other weather radars
in the system – which of course is part
of the overall Bureau of Meteorology
design.
The heart of the installation at Terrey Hills is a Meteor 1500S dedicated
S-Band Doppler weather radar, manufactured by AMS-Gematronik. It operates in the 2.8GHz band with a peak
power of 750kW.
The 8.5m linear horizontallypolarised dish has a gain of 45dB, 1°
half- power beam width and 26dB side
lobe suppression. It can scan between
0.2 and 6rpm but normally, the Terrey
Hills scan rate is set at 3rpm. It is accurate to 0.1° and is mounted inside the
protective fibreglass “radome”.
The radar transmitter features a fully
solid-state modulator which drives the
VKS 8387 klystron tube. The klystron
system, together with a coherent receiver, offers up to 20dB improvement
in stability and clutter suppression
compared to older, coaxial magnetrons.
Other advantages of the klystron
transmitter included high average and
peak power, high gain, high efficiency,
longer pulse duration and sufficient
control of the waveform and frequency.
The “Golf Tee” tower
The 20m tower, which weighs in at
about 60 tonnes, is made up of a bolt
cage foundation, base, column, conical
sections, a radar “floor” and topped by
a 11m diameter fibreglass radome. The
tower itself is 3.8m in diameter and
the conical section at the top is 7.2m
in diameter.
It was manufactured by Melbourne-
As a storm, it was only a tiddler. The colours show the rain rate – only a few patches of red, mostly greens, blues and
greys. This half-hour “loop” from 04:18 to 04:48 UTC (3:18 to 3:48pm Sydney time) tracks the path of rain across the city.
This one is also slow-moving: storms often move right through the area and out to sea in that 30-minute timeframe.
www.siliconchip.com.au
siliconchip.com.au
January 2010 23
Remember Tropical Cyclone Larry, which brought so much devestation to North Queensland in March, 2006 (who could
forget the price of bananas). Here Larry is being tracked by the Townsville weather radar (265km away) as it develops out
in the Coral Sea and then finally comes ashore right over Innisfail. One surprising aspect of these radar images is the lack
of rain intensity – not much above moderate. But if you’ve ever been caught in a cyclone, you’ll know it’s a tad more!
based Eliot Engineering, who also
manufactured the towers at Melbourne
and Brisbane.
How it works
Contrary to what you might expect
(having seen radar at airports, etc),
as well as spinning in the horizontal
direction weather radar antennas also
move in the vertical direction. From a
minimum of 0.5° above the horizontal,
each rotation of the “dish” increases by
0.5° to build up a “3D” image.
If this wasn’t done, the radar image
would effectively be at one particular
elevation. And as we all know, rain
clouds/storms don’t scud along at a
single convenient height.
Depending on the type of cloud
or storm it could be anywhere from
virtual ground level right up to tens of
thousands of metres.
Hence the dish moves to capture
the various heights. The hardware
and software to control this is quite
low level – in fact, a standard 512MB
2GHz PC is used running proprietary
“Ravis 1500” software. Radar images
are first processed on site by “Aspen
DRX” signal processor software.
There is an enormous amount of information contained in the reflected radar images. For example, there’s always
clutter and false images which need to
be analysed and if possible eliminated
(although that’s not always practical).
And of course, there is the integration of the various radar sweeps to
form a single, coherent image. All this
requires significant computer grunt, not
to mention some pretty smart software.
As a standard tool for the meteorological user, AMS - Gematronik has
developed a powerful and versatile
software package, fittingly enough
Joining the two sections
involved lining up the bolt holes.
November 2008: The first
5m tower section in place
24 Silicon Chip
Lowering the 5m pedestal that
allows the radar dish to rotate.
siliconchip.com.au
It’s important that the radar site has an unobstructed view. This semi-fisheye shot is looking towards the west.
called “Rainbow”. This offers the integration, processing and distribution of
any kind of meteorological data and for
remote control of weather radars within
a meteorological network.
Warnings
While duty forecasters will always be
monitoring their screens at the various
meteorological offices (each capital
city), much of the information coming in can trigger warnings which the
duty forecasters can then act upon – for
example, issue warnings to the media
regarding approaching storms, prepare
for possible floods, and so on.
The duty forecasters’ screens will
contain a lot more information than
radar images but radar is a very important tool in getting the message out to
the public about short-term weather.
The highly-skilled operators can
identify a lot of varied information
February 2009: Installing the 8.5m
radar dish onto the pedestal.
siliconchip.com.au
from weather radar that the untrained
person would probably miss completely – for instance, southerly busters
(very common in Sydney in summer),
differences in thunderstorm types,
hail, rotational super-cells.
While the various BOM weather
radar websites are very popular at the
best of times, during storms or other
weather events usage shoots up virtually exponentially.
Thunderstorm warnings, for example, not only use the information from
the weather radars (and other measuring equipment, some at the weather
radar site but also located right across
the country) and are automatically
plotted on maps on the BOM website,
with expected direction and intensity.
The software tracks the thunderstorm on radar for a couple of cycles
then projects its likely track.
Even the place names are automati-
cally generated and displayed so there
can be no doubt in viewer’s minds as
to location. Again, all this information
can be circulated to the mass media for
public warnings.
Lightning
One thing that radar does not detect
is lightning, basically because there is
nothing to reflect the beam back.
However, there are quite precise
methods of measuring lightning strike
location and intensity but these are not
functions the bureau performs.
Instead, private organisations provide this service either in real time or
as a delayed report.
Lightning strike measurement is a
fascinating subject in itself – SILICON
CHIP has featured a couple of articles
on the subject, the latest being in the
November 1996 issue (“LPATS – StrikSC
ing a Blow Against Lightning”).
March 2009: Placing the last of the
radome panels.
January 2010 25
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