Errors in the retrieval of thin-cloud optical parameters obtained with a two-boundary algorithm.

The effect of various errors on the retrieval of optical depth, integrated backscatter, and extinction-to-backscatter ratio in optically thin clouds by use of a two-boundary algorithm is discussed. Uncertainties regarding aerosol loading at the cloud base and top lead to relevant errors that are often larger than those produced by signal noise. Formulas expressing the errors in the lidar-derived optical quantities dependent on optical depth and aerosol uncertainties at the base and top are derived for different fitting procedures. A method for the reduction of errors in the case of consecutive cloud measurements is explored, consisting of the fitting of the retrieved optical-depth-integrated backscatter data to obtain a correct extinction-to-backscatter ratio.