Avionics News May 2017 - 19
S T O R Y
D A V E
H I G D O N
reen. Yellow. Red. Magenta. These colors graphiAirborne weather radar:
cally define weather intensity on weather radar
the weather world in real time
displays, whether seeing the images in aggregate
By now, most technicians and many pilots and citizens un- as seen on weather datalink graphics and broadcast sources
derstand how Doppler weather radar works. This specialized
- and on the displays of airborne weather radar systems
radar capitalizes on the Doppler effect to detect the velocity
installed in airline, general aviation and combat aircraft.
of objects at a distance. Doppler effect accomplishes this by
With the growth in Automatic Dependent Surveillancebouncing a microwave signal off the desired target - weather,
Broadcast use, flight crews increasingly learn the benefits
in this case - and analyzing how the object's movement alters
from the Flight Information Systemthe frequency of the reflected signal.
Broadcast and its datalink-delivered
The result: direct, highly accurate
Doppler weather radar, available via
measurements of the target's velocity
ADS-B In and subscription weather
relative to the radar.
Doppler allows radar to measure
Business pilots confess of their
the speed of wind within storms by
growing use of FIS-B's datalink to
measuring the speed of moisture,
"extend my weather vision" beyond
water droplets and debris within
what onboard weather radar delivers.
Not only is airborne weather radar
Modern Doppler airborne weather
limited in range, it also sees nothradar performs this task in real time.
ing off to the sides - or behind the
With airborne weather radar, pilots
can see weather ahead, learn cloud
What makes airborne weather
height, terrain height and the intenradar worth the expense, weight and
sity of the weather.
training, pilots say, is its immediacy.
Those color variations detailed
Datalink weather lacks that immeearlier correspond to the severity of
diacy - but it offers a much bigger
precipitation detected by the radar.
Green translates to mild precipitaDoppler systems can provide
tion; yellow to moderate; red to heavy
added capabilities, among them
and magenta to severe - in line with
short-range turbulence detection that
the way storms rated from Level 1 to
identifies turbulence in the atmoLevel 4. Airborne weather radar resphere by detecting particulates,
turns gauge cloud height so pilots can
such as precipitation or dust.
decide whether to maintain an altitude or request a change.
To pilots like this one, real-world weather situations reFor that 30-to-120-degree arc straight ahead of an aircraft,
quire real-time imagery when faced with inclement weather.
the image from Doppler digital airborne weather radar is
That means learning the strengths of airborne weather
considered highly accurate. The real-time nature of the image
radar along with its limitations - and how datalink weather
Continued on following page
complements the live radar.