Difference between revisions of "Angel"

From Glossary of Meteorology
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<div class="definition"><div class="short_definition">A [[radar echo]] caused by a physical phenomenon not discernible by eye at the [[radar]] site.</div><br/> <div class="paragraph">Angels may appear as [[coherent]] or [[incoherent echoes]]. When diffuse and incoherent appearing,  they are sometimes called [[ghost]] echoes. Angel echoes observed by radars with wavelengths of about  10 cm and less are usually caused by birds or insects. Radars with longer wavelengths and radar  [[wind profilers]], which operate in the [[UHF]] and [[VHF]] radio [[frequency]] bands, regularly detect echoes  from the optically [[clear air]] that are caused by spatial fluctuations of the atmospheric [[refractive  index]]. <br/>''See'' [[Bragg scattering]]; <br/>''compare'' [[clear-air echo]].</div><br/> </div>
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<div class="definition"><div class="short_definition">A [[radar echo]] caused by a physical phenomenon not discernible by eye at the [[radar]] site.</div><br/> <div class="paragraph">Angels may appear as [[coherent echo|coherent]] or [[incoherent echoes]]. When diffuse and incoherent appearing,  they are sometimes called [[ghost]] echoes. Angel echoes observed by radars with wavelengths of about  10 cm and less are usually caused by birds or insects. Radars with longer wavelengths and radar  [[wind profilers]], which operate in the [[UHF]] and [[VHF]] radio [[frequency]] bands, regularly detect echoes  from the optically [[clear air]] that are caused by spatial fluctuations of the atmospheric [[refractive index|refractive  index]]. <br/>''See'' [[Bragg scattering]]; <br/>''compare'' [[clear-air echo]].</div><br/> </div>
 
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Latest revision as of 16:23, 25 April 2012



angel

A radar echo caused by a physical phenomenon not discernible by eye at the radar site.

Angels may appear as coherent or incoherent echoes. When diffuse and incoherent appearing, they are sometimes called ghost echoes. Angel echoes observed by radars with wavelengths of about 10 cm and less are usually caused by birds or insects. Radars with longer wavelengths and radar wind profilers, which operate in the UHF and VHF radio frequency bands, regularly detect echoes from the optically clear air that are caused by spatial fluctuations of the atmospheric refractive index.
See Bragg scattering;
compare clear-air echo.