A spectral limitation of the range resolved differential absorption lidar technique

The spatial distribution of the atmospheric parameters measured with the differential absorption lidar technique is restored for pulsed emission only if the laser emission is monochromatic. Due to the finite linewidth of the laser lines, a systematic error is introduced in the measurement of the local optical thickness, which is shown to depend on the propagation of the laser pulse along the line of sight and on the ratio of the laser linewidth to the absorption linewidth. Relative errors as large as 20 percent may be made under the usual experimental conditions for a laser linewidth/absorption linewidth ratio close to unity. A one percent limit on this error is only obtained if the laser linewidth/absorption linewidth ratio is equal to or less than 0.3.