Canadian weather radar network

The Canadian weather radar network consists of 31 weather radars spanning Canada's most populated regions. Their primary purpose is the early detection of precipitation, its motion and the threat it poses to life and property. Each has a range of 256 km (159 mi) in radius around the site to detect reflectivity, and a range of 128 km (80 mi) for detecting velocity patterns (Doppler effect).

History

Research in weather radars in Canada began at the end of the Second World War with "Project Stormy Weather"^[1]. After the war, J.S. Marshall continued at McGill University the work with the "Stormy Weather Group"^[2]. The Canadian network was thus gradually formed and by 1997, there were 19 weather radars of two kinds across the country: 18 five centimeter wavelength (C-Band) radars and 1 ten centimeter wavelength (S-Band) at McGill, all of the radars detected reflectivity with 3 sites equipped with Doppler capabilities (Carvel, King City and McGill).

Environment Canada received approval in 1998 to upgrade the network to Doppler standard and to add 12 more radars with the operational characteristics coming from King City Radar (CWKR), the research radar of EC^[3]. However, McGill radar (at the J. S. Marshall Radar Observatory), while being part of the network, is owned by McGill University. It is a research as well as an operational radar and is modified independently.

Characteristics

• McGill radar (at the J. S. Marshall Radar Observatory)^[4]:
  • 9 metre (30 feet) diameter antenna.
  • Using a klystron to produce a wavelength signal of 10 cm.
  • Doppler since 1993 and dual polarization was added in 1999.
• The rest of the network^[3] :
  • The upgraded radar have antennas from two manufacturers: Enterprise Electronics Corporation (EEC) and Raytheon.
  • The new radar have antennas produced by Andrew Canada. With a diameter almost double the old ones; resolutions improved by the same amount.
  • Use 5.6 cm wavelength emitting magnetrons.
  • Process received reflectivity and Doppler data with Sigmet Radar Data Systems.
  • Each radar in the network will thus be called a WSR-98E, WSR-98R or WSR-98A for Weather Surveillance Radar - 1998 (for the year of the start of the program) and the first letter of the manufacturer (Enterprise, Raytheon or Andrew).
  • Antennas of 3.6 meters in diameters for the ungraded radars and 6.1 m for the new ones.
  • Pulse length and pulse repetition frequency adjustable.

Scanning Strategy

Because the network is using C band radars, compromises had to be used (see Doppler dilemma) between maximum reflectivity range and maximum non ambiguous velocities. The actual scanning strategy (2006) is divided in two separate scans over 10 minutes^[3] :

• Conventional cycle: 24 elevation angles scanned in 5 minutes to obtain a tri-dimensional view of the atmosphere within 256 km of the radar in reflectivities.
• Doppler cycle: 4 angles scanned in reflectivity and velocities, the first three in a range of 128 km and the last within 256 km. This cycle is used to locate possible small scale rotation and shear in the wind pattern as well as the large scale circulation. The velocity data also help to filter artifacts in the reflectivity such as ground echos.

Only the McGill radar (J. S. Marshall Radar Observatory) using its coherent S-band transmitter acquires reflectivities and velocities during each of its 24 elevation angles: 5 minute cycle time^[4].

List of radars

The modernization process began in the fall of 1998 with the opening of Bethune radar and ended in 2004 with the one in Timmins ^[5].

See also

• NEXRAD, the weather radar network in United States

References

External links

• Environment Canada description of the different sites
• Real time Canadian weather radar network data by Environment Canada
• Andrew radars
• Enterprise Electronics Corporation (EEC)