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 $\text{γ}{}_{\mathrm{L}}\text{γ}{}_{\mathrm{a}}$ of the laser linewidth to the absorption linewidth. Relative errors as large as 20% may be made under the usual experimental conditions for $\text{γ}{}_{\mathrm{L}}\text{γ}{}_{\mathrm{a}}\text{≈ 1}$. A 1% limit on this error is only obtained if $\text{γ}{}_{\mathrm{L}}\text{γ}{}_{\mathrm{a}}\text{?0.3.}$