Difference between revisions of "Lidar ratio"

From Glossary of Meteorology
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== lidar ratio ==
 
== lidar ratio ==
  
<div class="definition">The ratio of the extinction cross section ([[scattering]] plus [[absorption]]) and the 180&deg; [[Backscattering_cross_section|backscatter cross section]], for either [[particles]] or molecules. For particles, it is usually used to characterize an ensemble having some distribution in size. It is generally written as <div class="display-formula"><blockquote>''S'' = ''σ'' / ''ß'',</blockquote></div>where ''σ'' is the [[extinction coefficient]] and ''ß'' is the value of the [[Scattering_function|scattering phase function]] at 180&deg;. The ratio ''S'' has units of steradian and can vary from as low as 1 to about 100 sr, depending on the type of particles.</div><br />
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<div class="definition">The [[lidar]] ratio is defined as the ratio of the [[extinction]]-to-[[backscatter]] coefficient, for atmospheric scatterers, which can be subclassified for either [[aerosol|aerosols]], molecules, or a combination of the two. It represents the ratio of the volume-extinction cross section ([[scattering]] in all directions plus [[absorption]]) and the 180° volume-backscatter cross section. It is generally written as <div class="display-formula"><blockquote>''S'' = ''σ''/''ß'' (total),</blockquote></div><div class="display-formula"><blockquote>''S''<sub>aer</sub> = ''σ''<sub>aer</sub>/''ß''<sub>aer</sub> (aerosol),</blockquote></div><div class="display-formula"><blockquote>''S''<sub>mol</sub> = ''σ''<sub>mol</sub>/''ß''<sub>mol</sub> (molecular),</blockquote></div>where ''σ'' is the [[extinction coefficient]] and ''ß'' is the value of the [[Scattering_function|scattering phase function]] at 180°. The lidar ratio ''S'' has units of [[steradian|steradians]] (sr) and can vary for common atmospheric scatterers from as low as 5 to about 100 sr, depending on the size distribution, shape, and chemical composition of the particles.</div><br/>
  
<div class="reference">Fernald, F., B. Herman, and J. Reagan, 1972: Determination of aerosol height distributions by lidar. ''J. Appl. Meteor.'', '''11''', 482–489, doi:10.1175/1520-0450(1972)011<0482:DOAHDB>2.0.CO;2.</div>
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<div class="reference">Fernald, F., B. Herman, and J. Reagan, 1972: Determination of aerosol height distributions by lidar. ''J. Appl. Meteor.'', '''11''', 482–489, doi:10.1175/1520-0450(1972)011<0482:DOAHDB>2.0.CO;2.</div><br/>
  
<p><br/>''Term edited 4 April 2017.''</p>
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<div class="reference">Weitkamp, Claus, Ed., 2006: ''Lidar: Range-resolved optical remote sensing of the atmosphere'', Vol. 102, Springer Science & Business, 456 pp.</div>
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<p><br/>''Term edited 31 March 2021.''</p>
  
 
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Latest revision as of 13:12, 31 March 2021



lidar ratio

The lidar ratio is defined as the ratio of the extinction-to-backscatter coefficient, for atmospheric scatterers, which can be subclassified for either aerosols, molecules, or a combination of the two. It represents the ratio of the volume-extinction cross section (scattering in all directions plus absorption) and the 180° volume-backscatter cross section. It is generally written as

S = σ/ß (total),

Saer = σaer/ßaer (aerosol),

Smol = σmol/ßmol (molecular),

where σ is the extinction coefficient and ß is the value of the scattering phase function at 180°. The lidar ratio S has units of steradians (sr) and can vary for common atmospheric scatterers from as low as 5 to about 100 sr, depending on the size distribution, shape, and chemical composition of the particles.

Fernald, F., B. Herman, and J. Reagan, 1972: Determination of aerosol height distributions by lidar. J. Appl. Meteor., 11, 482–489, doi:10.1175/1520-0450(1972)011<0482:DOAHDB>2.0.CO;2.

Weitkamp, Claus, Ed., 2006: Lidar: Range-resolved optical remote sensing of the atmosphere, Vol. 102, Springer Science & Business, 456 pp.


Term edited 31 March 2021.