Comment on two-wavelength lidar inversion techniques.

In a critique of two-wavelength lidar inversion techniques, Kunz [Appl. Opt. 38, 1015 (1999)] presented mathematical arguments that such techniques cannot yield unique solutions for extinction profiles. Ackermann [Appl. Opt. 38, 7414 (1999)] presented an analytical solution for the extinction profile from a two-wavelength lidar and also attempted to refute Kunz's mathematical arguments. However, the fundamental reasons why the authors of these two papers reached different conclusions were not fully uncovered. These previous papers are critically examined, and a new mathematical proof of uniqueness is provided. Further analyses are presented to explain how the technique works, along with comments on its limitations.