TERMINAL DOPPLER WEATHER RADAR

Presented By: Usama Ashraf ID: 110101001

INTRODUCTION

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.

HISTORY OF TDWR

• 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 ChinaFew airports with TDWR in the US are:• Chicago airport• Atlanta airport• Boston airport• Miami airport

AIRPORTS WITH TDWR

CHARACTERISTICS

• 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 Operating Frequency: The frequency at which TDWR operates and it

ranges within 5.6 to 5.65Ghz. Instrument Range Reflectivity: Reflectivity is generally refers to the

fraction of incident electromagnetic power that is reflected at an interface. 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.

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.

Peak Power: The amount of power transmitted by a radar during a given pulse.

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.

TDWR TECHNICAL SPECIFICATIONS

Operating Frequency

Operating Frequency 5.6 to 5.65 GHz

Instrumented RangeReflectivity 460 km

Doppler 89 km

Antenna Beamwidth 0.55°

Peak Power 250 kW

Pulse Length 1.1 μs

Clutter Suppression 60 dB

HAZARDSWind 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.

MICROBURST:

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.

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.

Conclusion: 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.

REFRENCES

• http://en.wikipedia.org/wiki/Terminal_Doppler_Weather_Radar

• http://en.wikipedia.org/wiki/Doppler_radar• http://en.wikipedia.org/wiki/Pulse-Doppler_radar• http://

www.ll.mit.edu/mission/aviation/faawxsystems/tdwr.html

• Doppler Radar - Classic Downburst Signature - YouTube.flv