From Glossary of Meteorology
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),
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.
Smol = σmol/ßmol (molecular),
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.