In the period from 2010 to 2021, in the village of Boyarsky on the eastern coast of Baikal Lake, studies were carried out on the vertical structure of aerosol fields in the troposphere. The measurements were carried out using the LOSA-M2 aerosol-Raman lidar in the summer (July - August). A total of 93 cycles of daily observations were carried out during this period. The report presents typical patterns of transformation of aerosol layers under various synoptic conditions. Particular attention is paid in the report to the relationship between the structure of the boundary layer and the direction of movement of air masses. With a southeasterly wind prevailing at the observation site and directed along the coast, a characteristic diurnal dynamics of the boundary layer is observed with the development of a mixing layer during daytime heating of the surface. When air masses formed above the cold surface of the lake are brought in, a layered structure without pronounced updrafts prevails.
The report presents the results of a numerical simulation of the optical properties of cirrus clouds containing quasi-horizontally oriented crystals, as observed by a scanning lidar. Two models of the spatial orientation of plate-like crystals in a cirrus cloud are considered. In the first model, the orientation of the crystals was determined by the normal law, while in the second case, it was determined by the exponential law. The numerical results were used to interpret the experimental observation data. It is demonstrated that the use of the exponential law leads to a better agreement between theoretical and experimental data, particularly at small scanning angles.
The report presents the results of observations of horizontally oriented crystalline particles in the clouds of the upper levels using a scanning polarization lidar. The measured dependence of the lidar signal on the lidar inclination angle is described by an exponential distribution and corresponds to the distribution of particle inclinations relative to the horizontal plane (flutter). Diffraction on the contour of the particles appears as a smoothing of the top of the measured distribution and depends on the size of the crystals. The effect of diffraction is significant for narrow distributions over tilt angles.
The article describes a new scheme for implementing a photodetector module based on an avalanche photodiode for registering lidar signals. An envisaged solution that allows to reduce the electromagnetic interference that occurs during the operation of the receiver in lidars. A feature of the device is the ability to adjust the voltage of the changing photodiode, which allows you to expand its range of coverage. The developed photodetector module is intended for use in lidars of the LOSA series.
Small-sized mobile lidars mainly use single-frequency sounding with registration of elastic backscattered radiation on aerosols. Mie-Raman lidars are used to correctly reconstruct the optical characteristics of an aerosol. The method most widely used in such lidar measurements for evaluating optical properties is the method of recording vibrational Raman scattering on nitrogen molecules. The disadvantages of this method are the low backscattering cross section and the significant frequency shift of the Raman vibrational component. These problems are solved by using purely rotational Raman scattering, which is characterized by a higher backscattering cross section, and a much smaller frequency shift, which practically eliminates the dependence on the Angstrom exponent. The paper presents the practical implementation of pure-rotational Raman measurements in the mobile lidar "LOSA-A2".
In September 2020, a complex experiment was carried out to study the composition of the troposphere of the Russian sector of the Arctic using the measurement-information system of the aircraft-laboratory TU-134 "Optic". The system includes a mobile lidar LOSA-A2, designed to measure the characteristics of atmospheric aerosol. When flying over the seas, the technical data of the lidar make it possible to sounding the water column and evaluate the primary optical characteristics (attenuation index, depolarization) in the surface layer of the sea. For this experiment, the lidar was additionally equipped with a channel for recording laser-induced fluorescence at a wavelength of 685 nm, which made it possible to determine the relative concentration of chlorophyll in the surface layer of the sea. The report presents preliminary results of assessments of the optical characteristics of the surface layer of the seas of the Russian sector of the Arctic.
The report discusses the possibility of studying aerosol pollutions over an urban area, including plumes from local sources, using scanning lidar systems. The main task is to reproduce the spatial structure of aerosol plumes and compare it with the topographic map of the city - 3D mapping. As an example of scanning aerosol emissions in the horizon plane, the results of observing the dynamics of the aerosol field over Tomsk, obtained by the LOSA-M3 lidar, are given.
The article presents the results of studying the horizontal orientation of crystalline particles, carried out using a scanning polarizing lidar LOZA-M3. Several series of measurements of the ice cloud structure in the zenith scan mode were carried out in Tomsk in May-July 2021. The dependence of signal intensity at small tilt angles (up to 5°) reflects the distribution of particle deflection relative to the horizontal plane, and is well described by the exponential dependence. Scanning up to angles of 45-50 degrees showed a high probability of the existence of the corner reflection in ice clouds.
The report presents the results of a comprehensive experiment on the study of the atmosphere over Lake Baikal, which was carried out in July - August 2019. Remote investigation of aerosol content in the troposphere was carried out using mobile lidars. One of the lidars was installed on board the research vessel «Academician Koptyug». The route of the vessel covered the entire water area of the lake. The second lidar for the entire duration of the experiment was located on the southeastern shore of Lake Baikal. The period of the experiment coincided with extensive forest fires in Eastern Siberia. The lidar data made it possible to reconstruct the spatiotemporal distribution of the smoke aerosol over the Baikal water area and estimate its optical depth, the values of which, in extreme cases, reached up to τ ≈4.
Between 2011 and 2017 complex experiments on lidar sounding of the atmosphere were conducted on the territory of Akademgorodok (Tomsk, 56°28'N, 85°E), accompanied by the launch of meteorological balloons. A total of 45 radiosonde sessions were conducted using Vaisala R92SGP radiosondes in the daytime and at night. WE compared the vertical moisture profiles and the profiles of backscattering coefficient. In most cases aerosol layers are present at altitudes where a local increase in relative humidity is observed. However, in 10 cases out of 45, the location of the aerosol layers on the records does not coincide with the position of the wet layers. The report provides several examples of such records, discusses the possible conditions for the occurrence of such phenomena.
A site for year-round monitoring of the atmospheric parameters by means of a lidar was installed in Tomsk in the frameworks of the Russian-French cooperation between the Institute of Atmospheric Optics and the LATMOS (Sorbonne Université) Laboratory, under the CNES EECLAT European project. For this purpose, a CE-372NP micropulse lidar at the wavelength of 808 nm was designed in the French company CIMEL Electronique under the project of the LATMOS staff. It is capable of carrying out eye-safe continuous sounding of the atmosphere in almost any climatic conditions in an automated mode. The main purpose of this installation is to obtain long-term series of altitude profiles of backscattered radiation from the aerosol component of the lower troposphere in order to obtain information on the height of the atmospheric boundary layer, retrieval of its optical thickness and lidar ratio in combination with the CIMEL CE-318 sunphotometer data. An intercomparison was made between the lidar CE-372NP of CIMEL and the stationary lidar LOSA-S of the Institute of Atmospheric Optics. For long-term continuous measurements of atmospheric parameters, lidar was installed on the territory of the Observatory “Fonovaya” of the IAO SB RAS, which is located in the background area of the Tomsk Region.
A description of a complex optical experiment using the means of remote laser sensing and local control for researching the physical processes of the formation of aerosol fields of the atmospheric boundary layer is presented. Examples of joint atmospheric sounding using ground-based and space-based lidars (CALIPSO lidar), as well as ground-based lidarphotometric studies are given. The technique of processing lidar-photometric data during the recovery of optical and microphysical parameters of atmospheric aerosol, including the recovery of vertical profiles, is discussed.
The article presents the results of observations of the crystalline cloud polarization structure carried out in Tomsk in April-October 2018. Scanning lidar LOSA-M3 makes it possible to measure the polarization characteristics of backscattering signals from aerosol and clouds at wavelength 532 and 1064 nm. Zenith scanning was carried out at a rate of 0.5 degrees per second, which corresponds to a shift in the direction of sounding by 2 minutes between laser pulses. The results show that the degree of horizontal orientation of the particles can vary significantly in different parts of the cloud. The dependence of the scattering intensity on the inclination angle is well described by the exponential dependence. The values of cross-polarized component in most cases shows a weak decline with the angle, but its change are smaller than the measurement errors. We can conclude that it is practically independent on the inclination angle. The scattering intensity at a wavelength of 532 nm has a wider distribution than at 1064 nm.
Scanning polarization lidar LOSA-M3 is designed to study of the optical characteristics of crystal clouds of the upper and middle layers at two wavelengths - 532 and 1064 nm. Lidar allows you to smoothly change the angle of inclination from the vertical with simultaneous conical (azimuthal) scanning. Such a measurement scheme makes it possible to study in detail the preferential orientation of ice crystals in the clouds. The lidar simultaneously measures the polarization characteristics of signals for linear and circular initial polarizations, which allows to obtain additional information about the anisotropy of scattering particles, including exploring the azimuthal orientation of the particles. The first results of observations of the crystalline cloud polarization structure carried out in Tomsk in April-October 2018 are presented in the article. The results show that the contribution of horizontally oriented particles giving a specular reflection can vary significantly in different parts of the cloud.
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