Depolarization lidars are widely used for the study of clouds and aerosols because of their ability to discriminate between spherical particles and particles of irregular shape. Depolarization of cloud backscatter can be caused also by the multiple scattering events. One of the ways to gain information about particle parameters in the presence of strong multiple scattering is the measurement of azimuthally dependent polarization patterns in the focal plane of receiver. In this paper we present an algorithm for the calculation of corresponding polarized patterns in the frame of double scattering approximation. The computations are performed for different parameters of scattering geometry, e.g. cloud base and sounding depth. Intensity distribution of depolarized component is of cross-shape and rotated at 45 dg with respect to laser polarization. The use of a properly oriented cross-shape mask in the receiver focal plane allows removing a significant portion of depolarized component produced by double scattering. To verify it experimentally, cloud depolarization measurements were performed with different orientations of cross-shape mask. Results obtained from measurements are in qualitative agreement with the model prediction.
Intensity distribution of Doubly Scattered Polarized Laser Radiation in the Focal Plane of Lidar Receiver
DI GIROLAMO, Paolo;
2006-01-01
Abstract
Depolarization lidars are widely used for the study of clouds and aerosols because of their ability to discriminate between spherical particles and particles of irregular shape. Depolarization of cloud backscatter can be caused also by the multiple scattering events. One of the ways to gain information about particle parameters in the presence of strong multiple scattering is the measurement of azimuthally dependent polarization patterns in the focal plane of receiver. In this paper we present an algorithm for the calculation of corresponding polarized patterns in the frame of double scattering approximation. The computations are performed for different parameters of scattering geometry, e.g. cloud base and sounding depth. Intensity distribution of depolarized component is of cross-shape and rotated at 45 dg with respect to laser polarization. The use of a properly oriented cross-shape mask in the receiver focal plane allows removing a significant portion of depolarized component produced by double scattering. To verify it experimentally, cloud depolarization measurements were performed with different orientations of cross-shape mask. Results obtained from measurements are in qualitative agreement with the model prediction.File | Dimensione | Formato | |
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