Observing atmospheric winds with a Doppler lidar
Most lidar systems used for atmospheric probing (see the associated articles in this issue) measure the intensity of laser radiation backscattered from the atmosphere to provide information on parameters such as aerosol structure, atmospheric density, or trace species concentration. Doppler lidars are designed to measure the frequency as well as the intensity of backscattered radiation. By comparing the frequency of the backscattered radiation to that of the transmitted laser pulse, the frequency change due to the motion of the scatterers (Doppler shift) can be computed and used to infer the component of scatterer velocity along the line of sight of the lidar. Since the particles that effectively scatter laser light are very small (less than a few micrometers in diameter), they move with the wind; hence, measurement of the mean velocity of a volume of scatterers provides a measurement of the mean radial wind speed at the location of the scattering volume.
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