Presented By: Usama Ashraf
ID: 110101001
Terminal Doppler Weather Radar
(TDWR):
TDWR is a doppler weather radar system
used primarily for the detection of hazardous
wind shear conditions , microburst and bird
strike on and near major airports in the United
States America.
Developed in 1990’s at lincoln laboratory
MIT
• Funded by United States America FAA
• As of 2011,there were 48 active radars
• Used by United States and China
Few airports with TDWR in the US are:
• Chicago airport
• Atlanta airport
• Boston airport
• Miami airport
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Operating frequency 5600-5650 MHz
Angular resolution beam 0.55 degree
Instrument range (reflective) 135-460
km
Instrument range (Doppler) 90 km
Near surface scans at 0.1-0.3 degree
Composite scans in 6 mints at various
degrees
TDWR Technical Specifications
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Operating Frequency: The frequency at which TDWR operates and it
ranges within 5.6 to 5.65Ghz.
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Instrument Range Reflectivity: Reflectivity is generally refers to the
fraction of incident electromagnetic power that is reflected at an interface.
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Instrument Range Doppler: Radar send a beam of a microwave signal
towards the desired target and listening for its reflection then analyzing how
the frequency of the returned signal has altered by object motion.
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Antenna Beamwidth: Its basically the angle between the half power of
main lobe. Its expressed in degree .It is expressed for horizontal plane and
can also be expressed for vertical plane.
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Peak Power: The amount of power transmitted by a radar during a given
pulse.
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Pulse Length: Measure of pulse duration expressed in time.
Clutter Suppression: Clutter is a term used for unwanted echoes in
electronic system , particularly in reference to radar. Such echoes are
typically returned from ground,sea and rain and it can cause serious
performance issues with radar system.
Operating Frequency
5.6 to 5.65 GHz
Reflectivity 460 km
Instrumented Range
Doppler
89 km
Antenna Beamwidth
0.55°
Peak Power
250 kW
Pulse Length
1.1 μs
Clutter Suppression
60 dB
Operating Frequency
HAZARDS
Wind Shear:
Wind shear, sometimes referred to as wind shear or wind
gradient, is a difference in wind speed and direction over a
relatively short distance in the atmosphere. Wind shear can
be broken down into vertical and horizontal components.
Bird Strike:
Bird strikes are a significant threat to flight safety, and
have caused a number of accidents with human
casualties.
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A microburst is an intense localized downdraft
that is sometimes generated by a thunderstorm.
There are two types of microburst:Wet microburst
Dry microburst
They go through three stages in their life cycle:
the downburst, outburst, and cushion stages.
Advantages & Disadvantages
A NEXRAD weather radar is a 10 cm wavelength (2700-3000 MHz) radar
capable of a complete scan every 4.5 to 10 minutes, depending on the
number of angles scanned. Its resolution is 1.25 degrees in width and 250
meters in range. The non-ambiguous radial velocity is 62 knots up to
230 km from the radar.
 The range resolution of the TDWR is nearly twice that of the NEXRAD. This
will give much better details on small features in precipitation patterns,
particularly in thunderstorms, in reflectivity and radial velocity. However,
this finer resolution is only available up to 135 km from the radar; beyond
that, the resolution is close to that of the NEXRAD.
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Shorter wavelength of 5cm
Attenuation of signal
Difficult to detect in rain
Difference B/W TDWR &LLWAS
In 1993 LLWAS is replaced by TDWR
 Both tells about wind shear
 TDWR is more advance then LLWAS
 LLWAS is not installed in Europe now.
 They use TDWR for detecting wind
shear.
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Conclusion:
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If an aircraft inadvertently encounters a
microburst, wind shear and group of birds while
flying at low altitude, it may lose altitude rapidly
and not be able to recover in time to avoid a
crash.
In fact, a series of commercial aviation accidents
in the 1970s and 80s led the FAA to commission a
sensor capable of remotely detecting low-altitude
wind shear phenomena such as the microburst.
The resulting product was the Terminal Doppler
Weather Radar (TDWR), which is now deployed at
45 major airports around the USA.
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http://en.wikipedia.org/wiki/Terminal_Doppler_W
eather_Radar
http://en.wikipedia.org/wiki/Doppler_radar
http://en.wikipedia.org/wiki/Pulse-Doppler_radar
http://www.ll.mit.edu/mission/aviation/faawxsyste
ms/tdwr.html
Doppler Radar - Classic Downburst Signature YouTube.flv