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Studies of the spectropolarization characteristics angular dependencies of radiation reflected by the plant leaves allow to investigate the mechanisms of reflected radiation flux formation: the specular reflection on the leaf surface, the singly and multiply scattering within leaf, the leaf pigment absorption, and the cuticle refraction of radiation going out from the leaf. The polarization characteristics are most sensitive to the changes of plant structure as compared with the other factors. We have discovered and theoretically substantiated a spectral shift of a maximum of the polarization degree angular dependence.

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The lidar investigation of dense atmospheric formations such as clouds and fogs is ofgreat interest both for the fundamental and applied meteorology.This study is carried out in the region of the Sofia city in summer. The presence of two zones (a green area and a residential district) with different albedo can be considered as a peculiarity of the underlying surface along the sounding path. The study was performed using a polarization aerosol lidar. I. Variation ofthe optical characteristics of the fogTill about 09:OO (2.5 hours after the sunrise) an increase (from 2-3% to 10-12%) of the depolarization coefficient is observed along the sounding path. This variation is due to multiple scattering of the signal penetrating into the dense fog zone. This assumprion is being confirmed by the delay (about 400 ns) of the cross-polarized component with respect to the parallel one. As the day progresses and the solar radiation respectively increases, the optical density of the fog decreases. As a consequence a decrease of the depolarization coefficient values is observed.When the fog has completely rarefied the depolarization coefficient reached values of about 2.3% which is characteristic of a "clear" atmosphere. Delay of the mixing layer formationThe presence of fog usually leads to a delay of the mixing layer formation after the sunrise. The lidar system gives the opportunity of following the mixing layer height. So the delay of the mixing layer formation can be determined as well; in the case it was about 2 houn.In the paper a comparison is made between the experimental data about the mixing layer development in the case of fog presence and a theoretical model dealing with sunny day. The mixing layer development proceeds with the same rate (curve's slopes are equal) as that during a sunny day but with a certain delay (the curves are shifted one with respect to another).The influence of the underlying surface on the optical characteristics and on the rate ofthe fog rarefying is determined from the lidar data as well.The performed experiment proves that the lidar systems are right tools for investigation of the formation and development of dense atmospheric objects. Besides, such an information is of great importance for the road transport and the aviation. CTu183Telephone: (017) 226-57-74. Fax (017) 226-59-40.The polarization characteristics of radiation reflected by the plant leaves are most sensitive to the changes of plant structure as compared with the other factors Studies of the spectropolarization characteristics angular dependencies of radiation reflected by the plant leaves allow to investigate the mechanisms of reflected radiation flux formation: the specular reflection on the leaf surface, the singly and multiply scattering within leaf, the leaf pigment absorption, and the cuticle retiaction of radiation going out tiom the leaf.The laboratory goniometer plant has been built up for receiving angular and spectral dependencies of the reflected radiation polarization characteristics on the base of production-type...