The Doppler Effect in Meteorology Carmen Fragapane A

The Doppler Effect in Meteorology Carmen Fragapane

A Little Introduction… n n 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.

So How Does the Doppler Effect Work?

Sounds Waves and the Doppler Effect

An Even Better Illustration…

Electromagnetic Radiation and the Doppler Effect

Radar and the Doppler Effect in Meteorology n n n 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 wind’s velocity. So…if 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.

The Doppler Effect in Meteorology n n n 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.

A Doppler Radar Tower

Light From Distant Cosmic Objects is Doppler Shifted Sun’s optical spectral lines The same spectral lines seen in a distant galaxy cluster shifted to a longer wavelength / lower frequency by the Doppler Effect

Doppler Lesson Site n http: //webphysics. davidson. edu/Applets. html