Recent news
Cloud microstructure effect on the polarization state of lidar signal
- National Research Tomsk State University, Russia
Propagation of optical radiation in the atmosphere depends on the phase
structure, and, in the presence of crystalline particles, even on their
orientation in space, which is largely determined by crystal sizes.
Propagation of laser radiation in clouds is accompanied by multiple
scattering of light, which leads to a significant change of intensity
value and of the polarization state of the detected radiation. According
to Mie theory, the polarization state of the reflected beam is not changed
compared to the original radiation if the particles are spherical and
homogeneous. Therefore, if a crosspolarized component appears in the lidar
reflected signal when aerosol is being sensed by linearly polarized
radiation, than it is caused either by nonspherical and anisotropic
particles or by multiple scattering.
Multiple scattering in lidar signal is not an easy task and today it is,
in general, unsolved. The results of studies of the lidar power structure
by Monte Carlo method has shown, that the double scattering approximation
is enough for laser sensing of cirrus. In this case the Stokes parameter
of lidar signal is equal to the sum of Stokes parameters determined by
single and double scattering.
The report presents the results of the calculation of the polarization
ratio of lidar signal due to the double scattering of clouds with
different microstructures. The effect of particle microstructure on the
polarization characteristics of lidar signal is discusses.
The work was supported by the RFBR (N11-05-01200а) and the Ministry of
Education and Science of Russian Federation (government contract
N14.518.11.7053 and N14.515.11.0032).