How Radar works
What is RADAR?
RADAR stands for RAdio Detecting And Ranging and is based on the use of microwaves that are sent out from a transmitter in a series of pulses.
How it works
The transmitter creates a pulse, sent out by a curved antenna, which focuses the waves into a precise and narrow beam. The antenna rotates as it sends out the pulses, enabling the radar to 'see' over a large area. As the pulses move out from the transmitter they intercept objects in the atmosphere – such as rain drops, hail or snow – these reflect energy back to the RADAR. To detect these particles, the antenna rotates once every 30 seconds to make measurements at 14 different elevations. These multiple angle scans are then combined into a Constant Altitude Plan Position Indicator, or CAPPI, image. The amount of reflected energy received by the RADAR depends on the size and shape of the particles, the number of particles and whether they are liquid (water) or solid (ice).
Radar images
The received data is detected, then amplified and turned into a video signal by a receiver. The receiver assigns an approximate rain rate for each signal it receives and that rain rate has a colour assigned to it. The completed image is then sent to the web. These images are updated every six or 10 minutes, depending on the type of radar.
Doppler radar
Doppler radars differ from other radars, as they not only detect the presence of rain drops and other precipitation particles, they also detect the motion of those particles either towards or away from the radar.
They measure the speed at which the particles are moving, providing valuable information to forecasters and others about the severity of thunderstorms, the timing of wind changes and other phenomena which can’t be detected by normal radars.
More information is available on BoM's website.