Canada's radar network: weather networks tour

A dome containing the radar antenna sits on top of a tall metal tower above the treetops

The word radar is a shortened form of radio detection and ranging.  Radars use microwave energy to detect precipitation and its range or distance from the station.  Environment Canada has 31 Doppler radars in the Canadian network.  Doppler weather radars can do something ordinary weather radar cannot--they can detect the motion of precipitation droplets within a cloud. This information helps forecasters detect developing severe weather and issue earlier warnings.

Radar equipment is installed on towers like this one to raise it above objects on the ground that might otherwise block the beam.  A radar system has 2 main parts:  a transmitter and a receiver.  The slowly rotating transmitter sends out short bursts of microwave energy and then "listens" for the signal to be returned.  The energy beam will pass right through clouds and fog because their water droplets are too small to reflect the signal.  Larger precipitation particles will bounce some of the energy back to the receiver--this is called an echo.  The length of time it takes for the signal to be returned tells us how far away the precipitation is.  The amount of energy returned tells us how intense the precipitation is.  Doppler radar can also determine how fast the droplets are moving toward or away from the radar antenna, so that forecasters can identify the signs of a developing tornado.

The effective range of a radar is about 200 km in any direction from the antenna.  That means each of these systems can monitor an area 400 km across, as shown by the darker circles on this map.  To see if there's any precipitation in your area today, follow this link and select the radar closest to your location … but don't forget to come back and finish the tour!

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