The National Radar Program

Frequently Asked Questions

Questions About Doppler Weather Radar

What are the benefits of Doppler weather radar and how does it help us detect severe weather?

Doppler weather radar provides meteorologists with a powerful tool which helps in determining motion and structure within weather systems. Conventional weather radars indicate the location and intensity of precipitation. Doppler processing adds detailed information on the movement of precipitation within these meteorological systems.

Using Doppler data, meteorologists can identify and more precisely define the areas where severe weather is likely to occur. Dopplerized radar data helps detect patterns which are precursors of severe thunderstorms and tornadoes, violent gusting and mircrobursts within a developing storm. Dopplerized weather radar makes it possible to predict and detect severe weather and provide more advanced warning than was possible using conventional radar information.

Will Doppler weather radar prevent deaths from occurring because of tornadoes and other forms of severe weather?

Doppler weather radar enables the meteorologists to detect significant weather events more precisely and to provide more advanced warnings than previously possible.In situatons where minutes count, warnings of intense storms will be generated with more lead time to the public.

Does Doppler weather radar have other uses?

The new network of Doppler weather radars will enable meteorologists to provide better forecasts of significant weather events. Areas threatened by heavy rainfall can be identified more precisely and estimates of the maximum precipitation intensity given more accurately. These improvements can lead to better flood predictions which, in turn, will result in better management of storm sewer runoff, reduced episodic water pollution incidents and improved warnings to those threatened by floods. In fine weather conditions, bird and insect migrations can be observed. This information can be used by biologists and ecologists.

Do Doppler weather radars pose a health hazard to those living near them?

The radio-frequency exposure from Doppler weather radars is well below Health Canada radiation exposure safety guidelines. Under normal operating conditions with a rotating antenna the levels are about 50,000 times lower than the safe exposure limit and well below the levels associated with cell-phones.

Will the radars cause radio interference?

All of the meteorological radars forming the National Radar Program network operate in C-band except the McGill radar which operates in S-band.

MSC radars use a co-axial magnetron transmitter with a tuneable range from 5450 MHz to 5825 MHz., in compliance with international spectrum allocations. Frequencies used are co-ordinated by Industry Canada .

The parabolic dish antennae produce a narrow conical beam. The 6.1 m antennae has a nominal beamwidth of 0.65 degrees while the 3.6 meter units give a beamwidth of 1.1 degrees.

The radar transmitters operate in pulsed mode with pulse durations of 2 and 0.8 microseconds. The pulse repetition rates vary from 1200 to 250 pulses/second, depending on the operating mode. Higher pulse repetition rates are used with shorter pulses. The maximum sustained duty cycle for the magnetron is 0.001 in conventional mode and the peak power at the output of the magnetron is 250 kW. Based on the maximum sustained duty cycle, the maximum average power transmitted into the waveguide is 250 (250,000 x 0.001) W.

Weather radars operate in a continuous scanning mode. The antennae rotate continually in azimuth, changing the elevation angle after each complete azimuth rotation. The conventional volume scan typically lasts 5 minutes. If it is included in an elevation angle, any point within the volume scan is only swept by the beam of the antenna two or three times every five minutes.

All MSC transmitters are licensed by Industry Canada . If they are found to be a source of interference to other licensed users, Environment Canada is obligated to take corrective action.

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