Interpretation of the data from lidar studies of high-level clouds requires information on the vertical profiles of meteorological quantities. The nearest aerological stations to Tomsk are located at about 250 km away from the city and launch radiosondes only twice a day. The ERA5 reanalysis was considered as a source of vertical profiles, which provides higher spatial and temporal resolution. It is compared with the aerological data, and the possibility of its using was evaluated in this research.
The results of complex lidar-actinometric experiments to study of the optical properties of high-level clouds (HLCs) and their effect on the solar radiation fluxes measured near the Earth's surface are described. Optical, microphysical (orientation of ice particles), and geometric characteristics of natural and anthropogenic (contrails) HLCs are estimated according to the data on polarization laser sensing. It is shown that the crystal orientation in cirrus affects significantly the transmission of short-wave solar radiation.
Results of the joint lidar-actinometric experiment on the study of optical properties of high-level clouds and their effect on the solar radiation fluxes measured at the Earth's surface are described. Conclusions about the effect of specular clouds on a decrease in radiation fluxes compared to non-specular ones depending on the Sun’s zenith position are drawn.
Results of the experiments on polarization laser sensing of aircraft contrails performed with the lidar developed at the National Research Tomsk State University are described. The altitudes of the lower and upper borders, backscattering phase matrices, optical thickness, and scattering ratios of the observed aerosol formations are determined. Microstructure parameters of the contrails are estimated by comparing the elements of backscattering phase matrices not only obtained from lidar experiments, but also calculated theoretically. The meteorological conditions for the formation of the preferred horizontal spatial orientation of ice crystals in contrails are established.
In the paper the analyses of the lidar measurements data of optical parameters of the cirrus clouds over the Tomsk city are presented. The valuation of the microphysical properties of the cirrus clouds was done by the backscattering matrices that were measured by the high-altitude polarization lidar (wavelength is 0.532 μm) from National Research Tomsk State University in 2016-2018. For the interpretation of the laser sensing data we used the backscattering matrices database designed in V.E. Zuev Institute of Atmospheric Optics, Russian Academy of Sciences, Siberian Branch. An attempt to interpret the measured matrix using the quasi-horizontal orientated hexagonal columns with the 1000 μm modal size Lmod is incorrect in view of the fact that the particles with this size are very unlikely in existence of nature. It was demonstrated that the calculated backscattering matrices together with proposed algorithm could be used for the valuation of microphysical properties of the measured backscattering matrices.
In the present report, results of the experiment on polarization laser sensing of contrails performed for one and a half days are discussed. The altitudes of boundaries of the aerosol layers, their backscattering matrices, optical thicknesses, and scattering ratios are determined. The vertical profiles of lidar returns are analyzed. The results are compared with the meteorological data at the altitudes of formation of high-level clouds.
Determining the aerosol microphysical properties is an important scientific and applied problem. In practice, most often the interpretation of lidar data is based on the laser sensing equation, which is valid for media with a small optical thickness. During sensing of optically dense formations, it is necessary to take into account the contribution of multiple scattering to the lidar return. In addition to significant attenuation, multiple scattering leads to the depolarization of radiation. The purpose of the present report is to discuss the effect of the polarization state of sensing radiation on its extinction in water-milk suspension.
A complex experiment on the investigation of radiation characteristics of cirrus is performing since 2016. In the experiment, solar radiation fluxes are measured near the Earth’s surface and the orientation degree of ice crystals in cirrus is estimated using a polarization lidar. Results of the experiment are discussed. Significant effect of the orientation degree of cirrus particles on the transmission of solar radiation is found in a number of experiments.
The results of the investigation of radiation characteristics of cirrus consisting of crystalline ice particles with a preferred orientation are discussed. The orientation degree of particles is estimated from the backscattering phase matrices, which are determined with the high-altitude polarization lidar developed at National Research Tomsk State University. It is shown that the orientation of ice crystals in clouds with anomalously high backscattering affects significantly the transmission of solar radiation.
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