Lidar Monitoring Research Articles

Features of the Thermal Regime of the Middle Atmosphere over Western Siberia from the Data of Many-year Lidar Monitoring

Features of the Thermal Regime of the Middle Atmosphere over Western Siberia from the Data of Many-year Lidar Monitoring

Results of lidar monitoring in the Vyborgsky district of the Leningrad region and St. Petersburg

, St. Petersburg, Russia,

Intraannual Dynamics of Background Stratosphere Aerosol over Tomsk According to Lidar Monitoring Data

The article analyzes data on the intra-annual variability of the vertical-temporal structure of the background aerosol and its integral content in the stratosphere, obtained at the lidar complex of the high-altitude atmospheric sounding station of the IAO SB RAS for 2022. As primary information for the analysis, a data array of 93 total signals accumulated was used on select nights. The interval of sounded heights extended from 10 to 50-60 km, the spatial resolution was 192 m. Reception of lidar signals was carried out in the photopulse counting mode with accumulation of 12×10^4 launches of laser pulses, the accumulation time of the total signal was 2 hours. The optical characteristic R(H) is the aerosol scattering ratio (H is the current height) as a parameter describing the vertical stratification of the aerosol. By definition, R(H) is the ratio of the sum of the aerosol and molecular backscattering coefficients to the molecular backscattering coefficient. Based on the monitoring results, as in previous years, a stable tendency for the accumulation of stratospheric aerosol in the cold season of the year was established with a maximum content in January and a decrease in the spring to virtual absence in June-July. From September, the aerosol content in the stratosphere begins to increase to its maximum value in winter. In the upper stratosphere (30-50 km) there is no background aerosol throughout the year. The article also presents the time dynamics of the complete filling of the stratosphere with background aerosol starting from 2017 to 2021 and supplemented by observations in 2022, expressed through the parameter of the integral aerosol backscattering coefficient B. В статье проводится анализ данных внутригодовой изменчивости вертикально-временной структуры фонового аэрозоля и его интегрального наполнения в стратосфере, полученные на лидарном комплексе станции высотного зондирования атмосферы ИОА СО РАН за 2022 г. В качестве первичной информации для анализа использовался массив данных из 93 суммарных сигналов, накопленных в отдельные ночи. Интервал зондируемых высот простирался от 10 до 50-60 км, пространственное разрешение составляло 192 м. Прием лидарных сигналов велся в режиме счета фотоимпульсов с накоплением по 12×10^4 запускам лазерных импульсов, время накопления суммарного сигнала – 2 час. В качестве параметра, описывающего вертикальную стратификацию аэрозоля, представлена оптическая характеристика R(H) – отношение аэрозольного рассеяния (H –текущая высота). По определения R(H) –отношение суммы коэффициентов аэрозольного и молекулярного коэффициентов обратного рассеяния к молекулярному коэффициенту обратного рассеяния. По результатам мониторинга, как и в предыдущие годы, установлена устойчивая тенденция накопления стратосферного аэрозоля в холодный период года с максимальным содержанием в январе и убыванием весной до практического отсутствия в июне-июле. С сентября начинается рост содержания аэрозоля в стратосфере до его максимально значения в зимний период. В верхней стратосфере (30-50 км) в течение всего года фоновый аэрозоль отсутствует. В статье так же представлена временная динамика полного наполнения стратосферы фоновым аэрозолем с началом от 2017 до 2021 г. и дополненная наблюдениями 2022 г, выраженная через параметр интегрального коэффициента обратного аэрозольного рассеяния B.

Numerical and experimental analysis of blade-tower clearance for large-scale wind turbines

With the increase of the rotor diameter and the flexibility of the blade, the efficient blade-tower clearance control becomes increasingly important. As a widely used strategy in the wind power industry to increase the blade-tower clearance, the fine pitch strategy still has the problem of power de-rating under typical operating conditions. Therefore, a novel coupled blade-tower clearance control strategy is proposed, combining the fine pitch strategy with a revised LiDAR monitoring system. Incorporating the LiDAR's characteristics and the operation modes of wind turbines, the LiDAR is designed to be installed at the front of the nacelle to monitor the real-time blade-tower clearance and feed back to adjust the pitch angle, allowing for safe operation of the wind turbine and maximizing output power. The reliability of the proposed strategy and the influence of weather on the strategy are verified through 22-day all-weather field tests on numerous wind turbines in a wind farm in China, nearly 100% of the efficiency can be achieved if conditions permit. Additionally, the strategy’s two trigger modes—the clearance threshold and data validity protection mechanism—are exemplified, demonstrating the efficiency of the proposed coupled blade-tower clearance control strategy.

INVESTIGATION INTO THE MECHANISMS OF CREST GROWTH ON GRAVEL BERMS

The continual sea-level rise predicted over the next century poses a significant threat to coastal regions. Preserving the coastline will require innovative coastal protection techniques and structures. A potential defence is to introduce artificial gravel beaches (Loman et al., 2010), or dynamic revetments (Bayle et al., 2020), a gravel berm placed at the high tide berm(Bayle et al., 2020). A key feature of these types of defences is their ability to maintain the berm elevation relative to the water level. As the water level rises, the structure is overtopped by waves which drives sediment up and over the berm crest peak. This leads to elevation gain for the berm and limits the landward excursion of waves. Berm crest behaviour has only been recorded at frequencies that do not allow wave-by-wave analysis of the process and the resultant ‘snapshot’ profiles may not be representative of the true variability of gravel berms. Through application of continuous 2-D Lidar monitoring on several active gravel berms this paper addresses this gap. It presents new findings related to sediment transport at the berm crest, the morphodynamic behavior under wave attack and a conceptual model for berm state.

Forecasting and Mitigating Rockfall based on Lidar Monitoring: A Case Study from Colorado

It is well-established that precursor movement that precedes large rockfalls can be detected by monitoring using repeated laser scanning (i.e., lidar), but there is a lack of documented cases that illustrate the practical application of this technology to forecast and help prevent large rockfalls along transportation corridors. In this paper, we present a case study in which routine lidar monitoring allowed a large (∼30 m3, ∼1050 ft3) moving block of rock to be detected before failure. Analysis of the lidar data allowed for historical movement to be evaluated, time to failure to be estimated, and quantification of the geometric and structural data necessary to design an effective mitigation scheme. The block movement was interpreted to be associated primarily with a planar sliding mechanism, and a limit equilibrium analysis was conducted to evaluate potential reinforcement schemes. Ultimately, a mesh and pattern bolt reinforcement system was installed. During rockbolt tensioning, PVC extensometers installed by the contractor showed closure of the fracture at the back of the block.

Lidar monitoring of the aerosol content in the near-ground atmospheric layers over Sofia

Lidar measurements provide possibility to determine and localize the sources of aerosol emissions in the air, to determine the presence of airborne transport of dust in the atmosphere, to track in real-time aerosol movement above vast territories [1-4]. Presently, along with building networks of ground lidar stations, such as the European Aerosol Research Lidar Network (EARLINET), it becomes more and more important to develop and refine the lidar methods of processing the data from measurements to retrieve the necessary information [5]. The present study comments on results of aerosols monitoring in the lowest atmospheric layers above Sofia by using lidar remote sensing. More than 20 lidar measurements were carried out in the period January – June 2022. The lidar system emitted laser pulses nearly horizontally within the planetary boundary layer (PBL); the reflected pulses were collected to calculate the range-corrected signals and to produce color-coded time-distance diagrams. These diagrams, superimposed on a map of the city to illustrate the location of the aerosol layers were published on the website of the Laser Radar Laboratory of the Institute of Electronics (IE-BAS) at: http://www.ie-bas.org/Departments/LidarData_Horizont/Quicklooks-Horizont.htm.

Lidar Monitoring of Magmatic Activity in the Small Chamber of the Elbrus Volcanic Center

Lidar Monitoring of Magmatic Activity in the Small Chamber of the Elbrus Volcanic Center

Optical Aerosol Model of the Western Siberian Stratosphere Based on Lidar Monitoring Results

Optical Aerosol Model of the Western Siberian Stratosphere Based on Lidar Monitoring Results

Process and perturbation in a high elevation alluvial system, Yosemite National Park, USA

High-elevation alluvial river environments are little studied by geomorphologists despite their sensitivity to disturbance and their critical role as the landform supporting montane meadow ecosystems. Here, we establish the fundamental fluvial functioning and legacy factors inherent to the upper Tuolumne River in Tuolumne Meadows (elevation 2620 m asl), Yosemite National Park, USA. Evidence was drawn from structured field reconnaissance, morphological surveys, and sediment analysis; integrated with LiDAR monitoring and assessments of flood frequency, flood inundation, and sediment transport potential. Results indicate a sinuous single-thread channel in dynamic equilibrium with fluvial processes but with reduced rates of meander activity over the past century. Geomorphic processes are dominated by the influence of snowmelt discharge, partly because atmospheric river events rarely influence this high elevation. Process intensity is thus directly related to snowpack depth with monitored bank erosion rates substantially higher following the deep snowpack of 2016–17. Diurnal cycling of flow means that bedload-transport potential scales very well with total annual discharge volume. The legacy of human activity is unique here, with perturbations caused primarily by early-to-mid twentieth century infrastructure development rather than typical patterns of watershed development. Pre-eminent was 1930s instream aggregate extraction for road improvements. In conjunction with naturally very low rates of sediment supply, the resulting pit is still only one-quarter full and could disconnect downstream sediment supplies for several centuries more. The gravel pit appears to explain incision of the upper channel reach and reduced rates of lateral activity farther downstream. Future impacts will be dominated by climate change, including the potential increased influence of atmospheric river events, reduced snowpack depth, and tradeoffs in sediment production and connectivity as headwater glaciers recede. The upper Tuolumne River and its meadow typify the unusual, but not singular, geomorphology of high-elevation alluvial rivers, whose high ecological and social values justify greater attention.

Methodology for Lidar Monitoring of Biomass Burning Smoke in Connection with the Land Cover

Lidar measurements of 11 smoke layers recorded at Măgurele, Romania, in 2014, 2016, and 2017 are analyzed in conjunction with the vegetation type of the burned biomass area. For the identified aerosol pollution layers, the mean optical properties and the intensive parameters in the layers are computed. The origination of the smoke is estimated by the means of the HYSPLIT dispersion model, taking into account the location of the fires and the injection height for each fire. Consequently, for each fire location, the associated land cover type is acquired by satellite-derived land cover products. We explore the relationship between the measured intensive parameters of the smoke layers and the respective land cover of the burned area. The vegetation type for the cases we analyzed was either broadleaf crops or grasses/cereals. Overall, the intensive parameters are similar for the two types, which can be associated with the fact that both types belong to the broader group of agricultural crops. For the cases analyzed, the smoke travel time corresponding to the effective predominant vegetation type is up to 2.4 days.

Influence of Absorption Cross-Sections on Retrieving the Ozone Vertical Distribution at the Siberian Lidar Station

The purpose of this paper is to study how the application of different sets of absorption cross-sections influence the ozone vertical distribution (OVD) in the upper layers of the troposphere—stratosphere in the altitude range ~(5–45) km, using a differential absorption lidar (DIAL), operating at the sensing wavelengths 299/341 nm and 308/353 nm. We analyzed the results of lidar measurements of OVD obtained in 2021 using meteorological data from the IASI/MetOp satellite at the Siberian Lidar Station (SLS). The retrieval was performed using the data of four groups concerning the absorption cross-sections: Gorshelev et al., Malicet et al., SCIAMACHY, and GOME. To estimate how the absorption cross-sections influence the OVD retrieval from lidar measurements, we calculated the average deviations between the profiles retrieved using different sets both in a particular case on 2 January 2021 and throughout 2021. Our study showed that, out of the four absorption cross-section sets, the data of Gorshelev et al. should be used for long-term lidar monitoring of the ozone. These data show a more discrete dependence of the absorption cross-sections on the temperature values, which is more urgent for tropospheric and stratospheric ozone measurements.

Observing system simulation experiment (OSSE)-quantitative evaluation of lidar observation networks to improve 3D aerosol forecasting in China

In order to evaluate the potential impact of an aerosol lidar monitoring network in China on improving air quality prediction, an observing system simulation experiment (OSSE) was conducted using the Weather Research and Forecasting Chemistry (WRF-Chem) model and three-dimensional variational (3DVAR) data assimilation (DA) system. The impact of lidar numbers and locations on DA performance was evaluated using sensitivity analysis. Three ground-based lidar monitoring networks with 590, 310, and 99 lidars were constructed based on the distribution of existing surface air pollution monitoring stations in China to study the added value of lidar measurements. Four assimilation experiments were conducted using varying aerosol extinction coefficient data (AEXT) from three lidar monitoring networks and surface particulate matter (PM) concentration data over a four-week period. The results showed that compared with only assimilating surface PM2.5, the correlation coefficient (CORR) of PM2.5 was significantly higher, the root mean square error (RMSE) and mean fraction error (MFE) were significantly lower, and the mean mass concentration was closer to the simulated observation after adding lidar profile measurements to the 3DVAR DA system. Additionally, the evaluation of DA with 590 stations indicated spatial differences in the improvement of the positive effect of assimilation. Overall, the improvement effects of assimilation in Central and East China were better than those in other regions. Finally, it was observed that the positive effect of DA on PM2.5 prediction increased with an increase in the lidar number. However, with an increase in the number of lidars, the improvement of the positive effect of DA decreased gradually. The results indicate that it is necessary to balance the forecasting effect and economic cost while establishing a lidar observation network.

Collection of excitation-emission-matrix fluorescence of aerosol-candidate-substances and its application to fluorescence lidar monitoring.

Fluorescence lidars have the potential to identify aerosols, but it seems that the basic data of the fluorescence spectrum of various aerosols appear to be inadequate for practical use in application of fluorescence lidar monitoring. We collected the fluorescence spectrum data of 61 powders with different substances as pseudo-aerosols and organized them as EEM (Excitation-Emission-Matrix) fluorescence data. Our interest was also in the artificial substances that are discarded around our surroundings and become aerosols. Four applications of the EEM fluorescence to fluorescence lidars were discussed; designing fluorescence lidars, reconstructing aerosol fluorescence spectrums measured by fluorescence lidar, searching for new substances for fluorescence lidar measurement, and developing a database of EEM fluorescence for identifying aerosol types measured by fluorescence lidar. All EEM fluorescence data and application software were stored in one USB memory and run in the BIOS (Basic Input/Output System) independent of a computer OS (Operating System) for ease of use. Aerosol identification software worked well in general, but we have also talked a bit about improvements.

Optical-aerosol model of the Western Siberian stratosphere based on lidar monitoring results

Optical-aerosol model of the Western Siberian stratosphere based on lidar monitoring results

Lidar Monitoring of Moisture in Biological Objects

Lidar Monitoring of Moisture in Biological Objects

Lidar monitoring of nitrogen and sulphur oxides molecules in ship power installation emissions. Computer simulation

The Raman lidar equation computer simulation for measurement of the nitrogen and sulphur oxides molecules at the low permissible concentration (LPC) level and above (in the range from 2.6 1018 to 1.1 1020m−3) in the atmosphere at the ranging distance up to 500 m in the synchronous photon counting mode and the choice of the optimal parameters of such a lidar variant have been fulfilled. It is shown that it is possible to register this concentration level for sulfur dioxide with the time duration of 616 s at the ranging distance of 500 m, for nitrogen dioxide - with 50 s and for nitrogen oxide only during measurement time up to 5000 s bythe Raman lidar sensing of all studied molecules in atmosphere at the 532 nm laser radiation wavelength.

LIDAR Monitoring of Urban Areas

LIDAR Monitoring of Urban Areas

Computational Geometry-Based Surface Reconstruction for Volume Estimation: A Case Study on Magnitude-Frequency Relations for a LiDAR-Derived Rockfall Inventory

Key to the quantification of rockfall hazard is an understanding of its magnitude-frequency behaviour. Remote sensing has allowed for the accurate observation of rockfall activity, with methods being developed for digitally assembling the monitored occurrences into a rockfall database. A prevalent challenge is the quantification of rockfall volume, whilst fully considering the 3D information stored in each of the extracted rockfall point clouds. Surface reconstruction is utilized to construct a 3D digital surface representation, allowing for an estimation of the volume of space that a point cloud occupies. Given various point cloud imperfections, it is difficult for methods to generate digital surface representations of rockfall with detailed geometry and correct topology. In this study, we tested four different computational geometry-based surface reconstruction methods on a database comprised of 3668 rockfalls. The database was derived from a 5-year LiDAR monitoring campaign of an active rock slope in interior British Columbia, Canada. Each method resulted in a different magnitude-frequency distribution of rockfall. The implications of 3D volume estimation were demonstrated utilizing surface mesh visualization, cumulative magnitude-frequency plots, power-law fitting, and projected annual frequencies of rockfall occurrence. The 3D volume estimation methods caused a notable shift in the magnitude-frequency relations, while the power-law scaling parameters remained relatively similar. We determined that the optimal 3D volume calculation approach is a hybrid methodology comprised of the Power Crust reconstruction and the Alpha Solid reconstruction. The Alpha Solid approach is to be used on small-scale point clouds, characterized with high curvatures relative to their sampling density, which challenge the Power Crust sampling assumptions.

Measurement of rock glacier surface change over different timescales using terrestrial laser scanning point clouds

Abstract. Topographic change at a given location usually results from multiple processes operating over different timescales. However, interpretations of surface change are often based upon single values of movement, measured over a specified time period or in a single direction. This work presents a method to help separate surface change types that occur at different timescales related to the deformation of an active rock glacier, drawing on terrestrial lidar monitoring at sub-monthly intervals. To this end, we derive 3D topographic changes across the Äußeres Hochebenkar rock glacier in the Ötztal Alps. These changes are presented as the relative contribution of surface change during a 3-week period (2018) to the annual surface change (2017–2018). They are also separated according to the spatially variable direction perpendicular to the local rock glacier surface (using point cloud distance computation) and a single main direction of rock glacier flow, indicated by movement of individual boulders. In a 1500 m2 sample area in the lower tongue section of the rock glacier, the contribution of the 3-week period to the annual change perpendicular to the surface is 20 %, compared with 6 % in the direction of rock glacier flow. Viewing change in this way, our approach provides estimates of surface change in different directions that are dominant at different times of the year. Our results demonstrate the benefit of more frequent lidar monitoring and, critically, the requirement for novel approaches to quantifying and disaggregating surface change, as a step towards rock glacier observation networks focusing on the analysis of 3D surface change over time.