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Project titleExperimental studies of the altitude structure of atmospheric aerosol fields over Lake Baikal, including during periods of extreme natural phenomena and technogenic impacts

AffiliationV.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science,

Research area 07 - EARTH SCIENCES, 07-605 - Radiation processes in the atmosphere

KeywordsAerosol pollution, Lake Baikal, laser sounding, lidar, polarization, elastic and Raman scattering

Annotation
Atmospheric aerosol largely determines the optical properties of the atmosphere and, along with greenhouse gases, is singled out by the Intergovernmental Panel on Climate Change as one of the key objects of research in the tasks of fundamental problems of climatology. Large-scale transfer of atmospheric pollution as a result of natural, anthropogenic emissions and various disasters is among the primary factors affecting both the environmental safety of vast regions of our planet and climate change. Therefore, the preservation of the quality of the environment, the safety of the population, countering environmental threats are key issues throughout the world. One of the most promising tools in atmospheric research is lidars, which make it possible to obtain the necessary information about the objects under study at a new qualitative and quantitative level. The implementation of various sounding methods with the help of lidars contributes to obtaining a large set of optical-physical quantities of the atmospheric components. The scope of the necessary studies can vary from local observations at one point (control of emissions from industrial enterprises, monitoring of the state of the atmosphere over cities) to the study of large-scale transport of atmospheric impurities (volcanic eruptions, forest fires, sandstorms). The importance of conducting atmospheric research over the territory of a unique natural object - Lake Baikal, included in the UNESCO World Heritage List, should be emphasized separately. Such features of Baikal as its large extent from the southwest to the northeast, a huge mass of water and mountainous surroundings, cause special climatic conditions and significant differences in the distribution of meteorological parameters in the atmosphere above its basin. In turn, the complex system of hollow circulation of air flows over the lake determines the mechanisms for the formation and transfer of atmospheric aerosol fields. In addition to the influence of natural factors, in recent years, the anthropogenic impact on the environment of Lake Baikal has been actively increasing due, first of all, to an increase in the tourist load in this region. In addition, one of the significant sources of pollution of the atmosphere and hydrosphere of Lake Baikal are smoke aerosol emissions from forest fires in Siberia, the number of which is increasing due to climate warming. In order to preserve the unique ecological system of Lake Baikal, the Government of the Russian Federation is carrying out active environmental protection activities aimed at reducing the negative impact on the environment of the world natural heritage site. In connection with the foregoing, this project, aimed at modernizing the aerosol-Raman lidar for remote sensing of atmospheric aerosol fields of natural and anthropogenic origin, improving the methods for interpreting and processing the information received, conducting a complex optical experiment, accumulating and analyzing experimental data on the vertical distribution of optical and microphysical properties of the atmosphere of Lake Baikal, taking into account the characteristics of this region, is relevant. As part of the project, a multi-frequency scanning polarization lidar will be modernized for remote sensing of the atmosphere, determining the position and movement of aerosol clouds, and for environmental monitoring of industrial emissions and atmospheric pollution. The use of elastic and Raman scattering signals at several wavelengths (530 nm, 532 nm, 607 nm, and 1064 nm) will make it possible to reconstruct both the optical parameters of the aerosol and its microphysical characteristics. Registration of signals will be carried out in analog and in counting-photon modes of operation at these wavelengths, in the night-time and daylight hours. The lidar being developed will correspond to the best world standards in terms of its main technical characteristics. Due to the proposed design solutions, the possibility of placing the lidar on mobile carriers (cars, ships, aircraft) will be implemented, allowing research in difficult expeditionary conditions to study the spatial distribution of aerosol fields both on local and regional scales. The automated scanning function will allow recording the spatiotemporal pattern of the distribution of the concentration of aerosol impurities. Simultaneous use of several wavelengths of radiation and registration of the polarization components of signals will make it possible to carry out the selection of technogenic and background aerosol formations, to identify their sources of origin (industrial emissions, forest fires, etc.). Additionally, when interpreting lidar data, available information obtained from various independent sources will be involved: means of local control of the atmosphere; databases on the altitude distribution of meteorological values in the atmosphere and synoptic maps for the region; trajectory analysis, using the HYSPLIT model. As part of the project, synchronous ground-based lidar and satellite (CALIOP lidar) experimental studies are also planned, with further comparison of measurement results to assess the state of the atmosphere on a regional scale. The modern competitive world-class lidar technologies created by the authors of this project, for the tasks of atmospheric research, will significantly expand the understanding of the processes of formation and propagation of aerosol fields in the atmosphere of Lake Baikal. The research results obtained in the course of the project will be of great importance for predicting and preventing possible climate and environmental changes.

Expected results
At the end of the project, the expected scientific results will look like this: 1. A mobile scanning multiwave polarization lidar will be upgraded to detect and study atmospheric aerosol fields. The lidar will be equipped with a two-coordinate scanning rotary platform developed as part of the project, which allows high-precision sloping and horizontal scanning (with a positioning accuracy of 1 arc minute), as a result of which it will be possible to obtain information about a two-dimensional spatial pattern of atmospheric parameters. A photodetector module will be created for detecting lidar signals in the near-IR region (based on an avalanche photodiode), which makes it possible to operate in a wide dynamic range. The use of the new receiver will reduce atmospheric interference and thus improve the accuracy of measurements, especially when working in the daytime in analog mode. 2. The methodology for retrieving aerosol parameters from multifrequency atmospheric sounding data will be improved. Due to the implemented technical possibility of recording signals simultaneously at several wavelengths, taking into account elastic and Raman scattering, laser-induced fluorescence, as well as by recording the polarization components of the signal, the set of recoverable optical and physical characteristics of the aerosol (such as the Angstrom index, color ratio, scattering ratio, depolarization ratio). The result will contribute to a more accurate selection of atmospheric aerosol impurities, for example, it will be possible to isolate an aerosol of anthropogenic or smoke origin, as well as to estimate the size and concentration of particles according to sounding data. 3. As a result of the procedures for calibration and mutual intercalibration of equipment based on field tests of the lidar, synchronously with other means of remote and local monitoring of the atmosphere (satellite observations, ground-based lidars, etc.), an assessment of instrumental measurement errors will be carried out. 4. As part of the integrated optical experiment using the physical effects of elastic and Raman scattering, new results will be obtained that will allow us to study the processes of formation of the vertical structure and optical properties of aerosol fields (especially in the region of temperature inversions) under the influence of atmospheric physical processes that have different temporal and spatial scales, from micrometeorological to synoptic regions of the spectrum, as well as those determined by the orography of mountainous terrain. 5. Based on the results of the research, articles will be published, including in journals indexed in the Web of Science, Scopus and RSCI databases, applications for patents for original technologies for atmospheric laser sensing will be submitted. The methodological and technical solutions developed within the framework of the project will be used in the actively developing lidar network of the CIS countries - CIS-LiNet. The results obtained will be used in international scientific programs, primarily in cooperation with the LATMOS Sorbonne University laboratory (France) and the Center for Optical Remote Sensing of the Institute of Physics of the National Academy of Sciences of Belarus. This will allow Russian technologies and research to strengthen their high positions at the global level.

Annotation of the results obtained in 2022
As part of the project, a new type of photodetector module was created, which makes it possible to register lidar signals in the near-IR region of the spectrum with high noise immunity and in a wide dynamic range. These advantages in comparison with known analogs were achieved due to such design solutions as the use of a block structure of elements inside the module, with spatial separation of functional units with pulsed elements relative to the analog path, as well as the implemented ability to adjust the bias voltage of the photodiode, due to which it became possible to receive distortion-free signals from both short and long distances. The developed photodetector module has been successfully tested as part of the LOSA-A2 lidar. A two-coordinate scanning rotary platform has been created to place the LOSA-A2 lidar on it, thanks to which it is possible to obtain information on the spatial and temporal distribution of the concentration of aerosol impurities in the atmosphere, in real time and with high position determination accuracy. Thanks to the use of positional non-contact magnetic sensors with a digital controller to determine the angular position in the horizontal and vertical planes, the positioning accuracy of the scanning platform is 1 minute of arc. The results of test tests of the modernized scanning lidar are obtained, which prove the effectiveness of the use of technical solutions implemented in the lidar system, even in difficult expeditionary operating conditions. An analysis of the previously accumulated long-term lidar data was carried out, which made it possible to reveal the features of the formation and transport of the vertical structure of atmospheric aerosol fields in the mountain basin of Lake Baikal, associated with the specifics of the complex mechanisms of air flow circulation over this territory. In particular, quantitative estimates of the relationship between aerosol layers at different heights were obtained. Altitude autocorrelation matrices calculated from the data of lidar measurements showed that in the atmosphere above the lake there is a single mechanism for the formation of aerosol layers up to heights of 1000 m, in cases of a stable general synoptic situation. Also, based on the technique of two-point temporal correlation analysis, estimates were obtained for the transfer time of atmospheric inhomogeneities between the points of location of two lidars at different heights, from the surface layer to the middle troposphere. While maintaining the general direction of transfer, the transfer time of atmospheric inhomogeneities at different heights can differ by several minutes. This fact confirms the need to take into account the influence of local features of the wind regime when predicting changes in the meteorological parameters of the atmosphere in the conditions of the Baikal basin.

Publications

1. Nasonov S.V., Balin Yu.S., Klemasheva M.G., Kokhanenko G.P., Nasonova A.S., Novoselov M.M., Penner I.E. Синхронные лидарные наблюдения пространственно-временной структуры атмосферного аэрозоля в прибрежной зоне озера Байкал Оптика атмосферы и океана, - (year - 2023)

2. Nasonov S.V., Novoselov M.M., Ryabinin A. A. Development of a photodetector module for recording signals in the near-IR region in an extended dynamic range PROCEEDINGS SPIE, Proc. SPIE 12341, 28th International Symposium on Atmospheric and Ocean Optics: Atmospheric Physics, 1234146 (year - 2022) https://doi.org/10.1117/12.2646547

3. Sergei Nasonov, Yurii Balin, Marina Klemasheva, Grigorii Kokhanenko, Mikhail Novoselov and Ioganes Penner Peculiarities of the Vertical Structure of Atmospheric Aerosol Fields in the Basin of Lake Baikal According to Lidar Observations Atmosphere, 14, 837, 1-7 (year - 2023) https://doi.org/10.3390/atmos14050837