Difference between revisions of "Mst radar"

From Glossary of Meteorology
 
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<div class="definition"><div class="short_definition">(Abbreviation for mesosphere&ndash;stratosphere&ndash;troposphere radar.) A type of [[wind profiler]] designed to measure [[winds]] and other atmospheric parameters up to altitudes of 100 km or more.</div><br/> <div class="paragraph">In the [[troposphere]] and lower [[stratosphere]] (up to about 30 km) the [[radar]] signal is returned from [[refractive index]] fluctuations produced by [[turbulence]] in the [[neutral atmosphere]] (''see'' [[clear-air echo|clear-air echo]]). In the upper stratosphere and lower [[mesosphere]] (between about 60 and 100 km) refractive index variations are strengthened by the strong vertical [[gradient]] in [[electron density]]. Because the [[scale]] size of the refractive index fluctuations must be of the order of one-half the radar [[wavelength]] ([[Bragg scattering]]), and the minimum scale size of turbulence increases with height from a few centimeters in the lower troposphere to several meters in the upper stratosphere and lower mesosphere, most MST radars have operated in the [[VHF]] band (typically 30&ndash;60 MHz, 5&ndash;10 m wavelengths). Very sensitive [[UHF]] radars can detect echoes from [[incoherent scattering]] ([[thermal]] or Thomson [[scatter]]) by electrons above 60 km. MST radars are characterized by high- powered transmitters and large antennas. (VHF antennas range from 100 to 300 m across.) Similar  wind profilers that lack the [[transmitter]] power and [[antenna]] area to detect returns from the upper stratosphere and the mesosphere have often been called ST (stratosphere&ndash;troposphere) radars.</div><br/> </div>
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<div class="definition"><div class="short_definition">(Abbreviation for mesosphere&ndash;stratosphere&ndash;troposphere radar.) A type of [[wind profiler]] designed to measure [[winds]] and other atmospheric parameters up to altitudes of 100 km or more.</div><br/> <div class="paragraph">In the [[troposphere]] and lower [[stratosphere]] (up to about 30 km) the [[radar]] signal is returned from [[refractive index]] fluctuations produced by [[turbulence]] in the [[neutral atmosphere]] (''see'' [[clear-air echo|clear-air echo]]). In the upper stratosphere and lower [[mesosphere]] (between about 60 and 100 km) refractive index variations are strengthened by the strong vertical [[gradient]] in [[electron density]]. Because the [[scale]] size of the refractive index fluctuations must be of the order of one-half the radar [[wavelength]] ([[Bragg scattering]]), and the minimum scale size of turbulence increases with height from a few centimeters in the lower troposphere to several meters in the upper stratosphere and lower mesosphere, most MST radars have operated in the [[VHF]] band (typically 30&ndash;60 MHz, 5&ndash;10-m wavelengths). Very sensitive [[UHF]] radars can detect echoes from [[incoherent scattering]] ([[thermal]] or Thomson [[scatter]]) by electrons above 60 km. MST radars are characterized by high-powered transmitters and large antennas. (VHF antennas range from 100 to 300 m across.) Similar  wind profilers that lack the [[transmitter]] power and [[antenna]] area to detect returns from the upper stratosphere and the mesosphere have often been called ST (stratosphere&ndash;troposphere) radars.</div><br/> </div>
 
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Latest revision as of 11:13, 11 May 2021



MST radar

(Abbreviation for mesosphere–stratosphere–troposphere radar.) A type of wind profiler designed to measure winds and other atmospheric parameters up to altitudes of 100 km or more.

In the troposphere and lower stratosphere (up to about 30 km) the radar signal is returned from refractive index fluctuations produced by turbulence in the neutral atmosphere (see clear-air echo). In the upper stratosphere and lower mesosphere (between about 60 and 100 km) refractive index variations are strengthened by the strong vertical gradient in electron density. Because the scale size of the refractive index fluctuations must be of the order of one-half the radar wavelength (Bragg scattering), and the minimum scale size of turbulence increases with height from a few centimeters in the lower troposphere to several meters in the upper stratosphere and lower mesosphere, most MST radars have operated in the VHF band (typically 30–60 MHz, 5–10-m wavelengths). Very sensitive UHF radars can detect echoes from incoherent scattering (thermal or Thomson scatter) by electrons above 60 km. MST radars are characterized by high-powered transmitters and large antennas. (VHF antennas range from 100 to 300 m across.) Similar wind profilers that lack the transmitter power and antenna area to detect returns from the upper stratosphere and the mesosphere have often been called ST (stratosphere–troposphere) radars.