The Doppler Effect in Meteorology

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The Doppler Effect in Meteorology

• Carmen Fragapane

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A Little Introduction

• Christian Doppler first proposed the effect in
  1842 for light waves.
• Confirmed experimentally by Christoph Ballot in
  1845 using sound waves - approaching sources gave
  off a higher pitch, and receding sources gave off
  a lower pitch.

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So How Does the Doppler Effect Work?
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Sounds Waves and the Doppler
Effect
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An Even Better Illustration
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Electromagnetic Radiation and
the Doppler Effect
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Radar and the Doppler Effect in Meteorology

• Radio Waves, being a form of electromagnetic
  radiation, also can exhibit the Doppler Effect.
• Radar waves are scattered off of a target in the
  atmosphere such as rain drops, which act as
  tracers for the winds velocity.
• Soif the wind is moving towards the radar, the
  returning radio waves will be shifted to higher
  frequencies, and if moving away from the radar,
  the radio waves will be shifted to lower
  frequencies.

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The Doppler Effect in Meteorology

• Radar (Radio Detection and Ranging) transmits
  microwaves to detect precipitation particles in
  the atmosphere (such as rain, snow, and hail).
• After a radar sends out a signal, it "listens"
  for returning signals. A returning signal, called
  an echo, occurs when the transmitted signal
  strikes and reflects off objects (raindrops, ice,
  snow, trees, buildings, mountains, birds, or even
  insects) within its path.
• Part of the reflected signal is received back at
  the radar. The amount and type of precipitation
  that is falling can be determined.

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A Doppler Radar Tower
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Light From Distant Cosmic Objects is Doppler
Shifted
The same spectral lines seen in a distant galaxy
cluster - shifted to a longer wavelength / lower
frequency by the Doppler Effect
Suns optical spectral lines
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Doppler Lesson Site

• http//webphysics.davidson.edu/Applets/Applets.htm
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