One important point of discussion in restoring infrastructure after the floods is a new Doppler weather radar.
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RADAR stands for RAdio Detecting And Ranging and is based on the use of radio waves. Radars send out electromagnetic waves similar to wireless computer networks and mobile phones.
The signals are sent out as short pulses which may be reflected by objects in their path, in part reflecting back to the radar.
It is used in weather because when these pulses intercept precipitation, part of the energy is scattered back to the radar.
Northern Queensland has two types of weather radar stations. There are high resolution weather radar in Mount Isa, Townsville, Cairns and Weipa. There are also "dedicated weather watch" radar stations in Longreach and Mornington Island.
A Doppler radar uses the Doppler effect to produce velocity data about objects at a distance. It does this by bouncing a microwave signal off a target and analysing how the object's motion has altered the frequency of the returned signal. This variation gives highly accurate measurements of the radial component of a target's velocity relative to the radar.
Radar output has two forms: reflectivity and velocity. Reflectivity is a measure of how much precipitation exists in a particular area. Velocity is a measure of the speed and direction of the precipitation toward or away from the radar. Most radars can measure reflectivity but you need a Doppler radar to measure velocity, hence the problem with the dedicated weather watch radars - and that's if they work.
According to the BoM, "dedicated weather watch" radars should be online at all times, with images updated approximately every 10 minutes, unless there are technical difficulties or scheduled maintenance.
We now know that the Longreach radar was down during the floods.
The other problem is that as you move further away from the radar, the returned echo becomes weaker.
This occurs because as the radar beam broadens with distance, the proportion of the beam that is filled with rain lessens and reduces the echo intensity.
Hence the need to fill the central north Queensland blackspot - and as a matter of urgency - Derek Barry