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by Enric Terradellas last modified Mar 24, 2017 12:58 PM


Comparison of backscatter at different wavelengths provides some indication of particle size. Finally, if polarized light is used, the non-spherical character of particles can be determined: since dust particles are usually less spherical than other aerosol types, the method allows distinction between mineral dust and other pollutants.

Lidar technology can be divided into elastic systems that measure at the frequency of the emitted light and non-elastic systems that monitor Raman-shifted frequencies.  The fundamental problem of elastic lidars is that clear-air scattering is not negligible in the near-visible range. This forms a problem of having one measured variable (the returned energy) and two unknowns: the particulate optical extinction and backscatter coefficients. This dependence necessitates the prescription of the ratio between both coefficients, that is, the lidar ratio. However, the lidar ratio connects two optical quantities that both depend on the wavelength of the incident light, the refractive index, and the aerosol size distribution.

There are several lidar networks. Two of them can be highlighted in our geographical domain:

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