Lidar Rayleigh-fit criteria

The talk explains how aerosol-free regions in a lidar signal can be
determined by means of the so-called Rayleigh-fit. Criteria based
on statistical analyses of the residuals are proposed and explained
in detail, which allow to assess the quality of the Rayleigh-fit.
Some of the methods can be used to develop quantitative criteria
for the uncertainty in the retrieved reference value for the lidar
signal inversion.