The lidar technique for remote analysis

Although optical probing of the atmosphere was established before the invention of lasers, the rapid development of laser technology, and more specifically the advent of 2-switching, has resulted in laser techniques replacing many of the early, conventional. 

Looking at the cross-section values, it becomes evident that just a modest Mie scattering contribution may swamp any Rayleigh or Raman contribution, because the Mie scattering cross-section is so high in comparison with the others. As a consequence, low concentrations or changes in concentrations of dust or aerosols can be detected. 

Resonance scattering (also known as atomic or molecular resonance fluorescence) exhibits relatively large cross-sections however, quenching of the fluorescence by the more abundant ground-state species at atmospheric pressure is responsible for low detected signals. Hence, this technique is more useful in low-pressure environments, e.g. to detect trace components in the upper atmosphere. When using absorption or fluorescence detection techniques the 

Because the cross-sections for Raman scattering are extremely small, it is used in lidar only for a few, specific applications due to its limited range and sensitivity (for one of those applications see the segment on stratospheric studies further below). 

The detection efficiency s(R,A) includes all geometrical and optical factors of the receiver arrangement. It can be separated into two different parameters one is related to the spectral characteristic s(A) of the detection channels (filters, monochromator, etc.), and the other, s(R), incorporates the geometrical properties, such as the overlap between the field illuminated by the laser and the telescope field of view. 

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