Lidar measurements of aerosol depolarization ratio

Lidar measurements of the aerosol depolarization ratio provide highly reliable informations to discriminate between spherical and non-spherical particles in the atmosphere and they can help to distinguish between liquid and solid phase aerosols. These measurements can be performed by using a linearly polarized laser source and a hardware configuration of the receiving system including two channels detecting simultaneously the backscattered light polarized in the parallel and orthogonal direction with respect to the laser beam. In these conditions the total depolarization ratio, i.e. the depolarization induced by both aerosols and atmospheric molecules, can be obtained if a calibration of the system is performed. In this paper three different calibration methods are described. For each method a sensitivity analysis is performed and the different contributions to the total error are evaluated by means of a numerical simulation. Results from numerical simulations allow comparing the performances of the three calibration methods in different atmospheric conditions.