Ask A Scientist General Science Archive

Question:  What is the doppler radar?
 carol l lly

Answer:
Radar detects precipitation. Radar sends out short pulses of
microwave energy. Some of this energy is reflected off rain
and snow and other objects in the atmosphere. This reflected
energy is displayed on a scope. Doppler radar has the added
advantage of being able to detect the motion of objects. Police
radar guns and radar at the baseball game to measure the speed
of a fast ball are Doppler radars. Doppler radar not only sees
the object, whether it is a ball, a car or a raindrop, but it
can also determine how fast the object is moving toward or away
from the radar beam. The radar is based on the Doppler principle.
The frequency of energy emitted from a moving object changes. A
simple example of this is if you stand by the railroad tracks and
listen to a train whistle. As the train approaches the whistle has
a high pitch, as the train passes the pitch lowers. Doppler radar
can measure the frequency shift of the radar energy of moving
raindrops and determine how fast they are moving. The advantage of
Doppler radar is its ability to detect the rotation inside a
thunderstorm that produces a tornado.
Allsopp - National Weather Service