From Wikipedia, the free encyclopedia
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 in radius around the site to detect reflectivity, and a range of 128 km for
detecting velocity patterns (Doppler effect).
Canadian weather radar network (Source: Environment Canada)
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. 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
-
- 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 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 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).
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:
- 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 help to filter artifacts in the
reflectivity, like ground echos, too.
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.
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
[3].
References
See also
External
links
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instrumentation |
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