dopplerlidar

Doppler lidar, or Doppler LiDAR, is a remote sensing technique that uses laser light to measure the velocity of particles in the atmosphere by detecting the Doppler shift of the backscattered signal. It yields line-of-sight wind speeds and can provide range-resolved information when scanning or using pulsed light.

The measurement principle relies on the Doppler effect. As illuminated aerosols or molecules move along or across the laser beam, the frequency of the returned light is shifted by an amount proportional to the radial velocity. The shift Δf is related to the velocity by approximately 2 v cos θ over the laser wavelength λ, where θ is the angle between the beam and the velocity vector. Coherent detection methods convert this small frequency shift into an electrical signal that can be analyzed to determine velocity with high sensitivity.

Configurations vary. Continuous-wave Doppler lidars use a steady laser to measure velocity along a single line of sight, while pulsed Doppler lidars emit short laser pulses to obtain range information via time of flight. Scanning or multiple fixed beams allow reconstruction of wind components and, in some systems, three-dimensional wind fields.

Common applications include meteorology, where Doppler lidars profile wind in the boundary layer and monitor turbulence; aviation safety, by detecting wind shear and clear-air turbulence; and wind energy, aiding turbine siting, control, and performance assessment. They are typically operated in the near-infrared (around 1.5 micrometers) or other wavelengths chosen for atmospheric backscatter efficiency.

Limitations include dependence on atmospheric backscatter (aerosol concentration) and weather conditions, eye-safety constraints, and system cost. When backscatter is weak or precipitation dominates, the signal-to-noise ratio and measurement accuracy can degrade.