The lidar complex of the small station for high-altitude atmospheric sensing of the V.E. Zuev Institute of Atmospheric Optics SB RAS has been used in studies of the atmospheric thermal regime from 1994. The measurements are performed systematically and provide obtaining the vertical profiles of the air temperature for altitudes up to 70 km with a resolution of 192 m. It is of interest to compare the results with the data from other sources. The ERA5 reanalysis of the European Centre for Medium-Range Weather Forecasts (ECMWF), which summarizes the global meteorological monitoring network based on the retrospective data, provides high spatial (0.25×0.25°) and temporal (1 h) resolution. In the present report, the seasonal and annual distributions of vertical profiles of the statistical values of temperature deviation over Tomsk are considered according to the ERA5 reanalysis data relative to the lidar measurements. In addition, a similar comparison of lidar data was performed for the data of the AURA research satellite.
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.
The results of a complex pyranometric-lidar experiment are discussed. The optical and geometric characteristics of the high-level clouds (HLCs) are estimated from the polarization laser sensing data. Scattered radiation was recorded in the near-zenith area using a zenith-directed pyranometer simultaneously with the lidar measurements. The change in the diurnal variation of the pyranometer signal at the time corresponding to the lidar registration of the HLCs with a preferred horizontal orientation of ice crystals (specular clouds) is shown.
Results of the experiments on laser polarization sensing of high-level clouds with anomalous backscattering (specular clouds) performed with the high-altitude polarization lidar developed at National Research Tomsk State University (NR TSU) with a short lidar return accumulation time (about 3 minutes) are described. It has been shown that the preferred horizontal orientation of ice crystals in clouds is manifested even at such a short signal accumulation time intervals. Interpretation of the results of the experiment with longer accumulation leads to the identification of a cloud as a specular one despite the presence of not only a specular, but also non-specular local areas in it.
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 complex lidar and actinometric studies of the characteristics of cirrus containing crystalline ice particles are discussed. The greatest attention is paid to clouds consisting of horizontally oriented ensembles of ice crystals. Orientation of the crystalline particles in clouds is estimated from the backscattering phase matrix, which is determined based on the data obtained with the polarization lidar directed vertically to the zenith. Solar radiation fluxes are measured using the standard methods with an actinometer and a pyranometer. It is shown that under certain weather conditions ice crystals at altitudes of cirrus formation can be oriented horizontally, which significantly affects the transmission of solar radiation.
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.
Optical models of high-level clouds (HLCs) used for calculation of radiation fluxes in the atmosphere are analyzed briefly. Results of the experiments on polarization laser sensing of cirrus performed with the lidar developed at the National Research Tomsk State University are described. Optical and microphysical characteristics of such clouds obtained from the results of measurements of their entire backscattering phase matrices are presented. It is shown that the orientation of crystals in the cirrus significantly affects the transmission of shortwave solar radiation. This fact proves incorrectness of the representation of real crystalline particles in HLCs with spherical particles with the corresponding effective radii during calculating the Earth’s radiation budget.
The software complex for automation of processing the results of the experiments on sensing of high-level clouds with the high-altitude polarization lidar developed at National Research Tomsk State University is described. The software performs the following operations: preliminary processing and visualizing experimental data; calculating optical and geometrical characteristics of the observed aerosol layers; downloading meteorological data corresponding to the place, date, and time of the lidar experiment; as well as forming summary report on the performed processing.
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.
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.
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.
Results of experiments on polarization laser sensing of high-level clouds performed at the high-altitude polarization lidar developed at National Research Tomsk State University are discussed. It is shown that orientation of crystalline ice particles in a cloud leads to different values of the measured depolarization ratio for the same cloud, which depends significantly on the azimuthal orientation of the polarization plane of sensing radiation.
Results of complex experiments, in which flows of solar radiation are measured near the Earth’s surface in the presence of cirrus cloudiness and the orientation degree of ice crystals in cirrus is estimated using a polarization lidar, are discussed. Significant effect of the orientation degree of cirrus particles on the transmission of solar radiation is found in a number of experiments.
Optical methods for determining the microstructure of a dispersed medium provide sufficient speed and accuracy of monitoring its parameters, without any changes in the volume of the sensing medium. However, the phenomenon of multiple scattering has a significant effect on the characteristics of the lidar return in the study of media with large optical dense. In this work we discuss the principles of the device for determining the microstructure of a scattering medium, based on the separation of the backscattered intensity from the total flux of scattered radiation. Also we present the result of the experiments.
The problem an estimation of influence the crystal orientation in the ice clouds on the radiation transmission is solved. The technique of synchronous measurements of total radiation with the calculation of the backscattering matrix cirrus clouds using lidar is provided.
KEYWORDS: Polarization, Clouds, LIDAR, Matrices, Atmospheric modeling, Interference (communication), Data modeling, Data corrections, Crystals, Chemical elements
Technique and software for processing of experimental data obtained with the high-altitude polarization lidar developed at National Research Tomsk State University are described.
Results of observation of the dynamics of evolution and decay of an aircraft condensation jet are described. Polarization lidar is used to determine the upper and lower boundaries of the aerosol layer, its optical thickness, scattering ratio, and backscattering phase matrix.
Joint analysis of the data on polarization laser sensing of cirrus obtained using the ground based polarization laser developed at National Research Tomsk State University (Russia, Tomsk) with the results of theoretical calculations is described. The possibility of estimation of the microstructure parameters of cirrus with a preferred orientation of ice crystals on the basis of comparison of the backscattering phase matrices obtained experimentally and calculated theoretically is discussed.
Optical properties of the cirrus cloud ice crystals with preferred azimuthal orientation are required for current numerical models of the Earth's radiation balance. Retrieving the orientation distributions function of the crystals from a vertically pointing polarization lidar measuring the full Mueller matrix is a very complicated problem because of lake of information. Lidars with zenith scanning can be used only to retrieve the properties of horizontally oriented particles. The paper shows that if the particles have preferred azimuthal orientation, the polarization lidars with azimuthal scanning should be used. It is also shown that all the elements of the Mueller matrix give no extra information compare to the depolarization ratio. Optical properties of preferred azimuthal oriented hexagonal ice columns with size from 10 to 1000 μm for wavelengths of 0.355, 0.532 and 1.064 μm were collected as a data bank.
Methodology for determination of the optical and geometric characteristics of clouds is described. Problems of processing data obtained in experiments on polarization laser sensing of the atmosphere are discussed. Technique for reduction of the phase matrices of cirrus obtained with the high-altitude polarization lidar developed at National Research Tomsk State University to the symmetry plane affixed to the preferred orientation of ice crystals in cirrus is described. The experimental data are compared with the data of numerical modeling of phase matrices in the physical optics approximation and meteorological conditions over the lidar at cirrus altitudes.
The paper presents the first results of observations of cirrus clouds by polarization lidars with conical scanning, which were developed in Hefei (China) and in Tomsk (Russia). The light scattering matrix of ice crystal particles of cirrus clouds has been calculated for the first by the authors within the framework of the physical optics approximations in the case of conical scanning lidar. It is found that in this case the Mueller matrix consists of ten non-zero elements, four of which are small and can’t be applied to interpret the azimuthal distribution of particle orientation. All the diagonal elements have a strong azimuthal dependence. Among the off-diagonal elements only one element M34 carries additional information for interpreting the azimuthal distribution.
Experimental results of polarization laser sensing of cirrus with anomalous backscattering are presented. The technique of determining the optical and geometrical characteristics of clouds is described. Experimental data are compared with the meteorological conditions at altitudes of cirrus above the lidar location and with the results of numerical modeling of phase matrices in the approximation of physical optics. The recurrence frequency of meteorological characteristics of “mirror” cirrus is estimated.
We present results of joint analysis of the data of high-level cloud sensing with a polarization lidar and satellite radiometer MODIS. The possibility of detection from space of cirrus clouds with preferred orientation of ice crystals is discussed.
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