Lidar: Resonance

This article summarizes the principles and practices of the resonance lidar techniques used to measure constituents, temperatures, and winds in the middle and upper atmosphere (70-150 km). The lidar equation is presented with a resonance solution that highlights the robustness of the technique due to the complete quantum mechanical description of scattering by atoms and molecules. The technique is illustrated with contemporary examples of high-resolution (100 m, 1 min) measurements of mesospheric metals, temperatures, and winds. These measurements allow estimation of the constituent, heat, and momentum fluxes that are crucial for understanding nonlinear coupling and transport.