INVERSION OF LIDAR SIGNALS WITH THE SLOPE METHOD

In homogeneous atmospheres, backscatter and extinction coefficients ar e commonly determined by the inversion of lidar signals by using the s lope method, i.e., from a linear least-squares fit to the logarithm on the range-compensated lidar return. We investigate the accuracy of th is method. A quantitative analysis is presented of the influence of wh ite noise and atmospheric extinction on the accuracy of the slope meth od and on the maximum range of lidar systems. To meet this objective, we simulate lidar signals with extinction coefficients ranging from 10 (-3) km-1 to 10 km-1 with different signal-to-noise ratios. It is show n that the backscatter coefficient can be determined by using the slop e method with an accuracy of better than approximately 10% if the exti nction coefficient is smaller than 1 km-1 and the signal-to-noise rati o is better approximately 1000. The accuracy in the calculated extinct ion coefficient is only better than approximately 10% if the extinctio n is larger than 1 km-1 and the signal-to-noise ratio is better than a pproximately 2000. If the atmospheric extinction coefficient is smalle r than 0.1 km-1, then it is not possible to invert the extinction from lidar measurements with an accuracy of 10% or better unless the signa l-to-noise ratio is unrealistically high.