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1
Huang, Guosheng, Mingli Wu, Zhen Qiao, Songping Fu, Qiujiang Liu, Xiaowei Huai und Pengcheng Yan. „Characteristics and Simulation of Icing Thickness of Overhead Transmission Lines across Various Micro-Terrains“. Energies 17, Nr. 16 (14.08.2024): 4024. http://dx.doi.org/10.3390/en17164024.
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The hazard of ice accretion on overhead power circuits is significant, yet predicting it is very difficult. The key reason lies in the shortage of sufficient observational data on ice thickness, and previous studies have also rarely taken into account micro-terrain and micro-meteorological conditions. In response to the challenge of simulating overhead line icing, this study introduces a new icing simulation technique that fully considers the effects of micro-terrain and micro-meteorology. For this technique, typical micro-terrains of overhead line areas are first identified by using high-resolution elevation data, and the icing thickness characteristics in different micro-terrains are analyzed. Subsequently, icing thickness simulations for different micro-terrains are conducted. The results indicate that during the icing process, the icing thickness ranges from 5 mm to 8 mm under three types of micro-terrain, namely, “uplift type”, “alpine drainage divide type” and “canyon wind channel type”, whereas the icing thickness is less than 5 mm in the “flat type” of micro-terrain. This finding suggests that the first three micro-terrain types facilitate icing on overhead transmission lines due to the condensation and uplifting effects of water vapor caused by terrain. However, flat terrain lacks the conditions necessary for water vapor accumulation and thus is not easy to form icing. The results are advantageous for the deployment of overhead power lines in intricate terrain. It is advisable to steer clear of regions susceptible to icing, and endeavor to install circuits in level territories whenever feasible. In addition, the simulated icing thickness under different terrains is in good agreement with the observations. Specifically, the correlation coefficient between simulated and observed icing thickness is significant at the 0.99 confidence level, and the deviations between them are within 0.5 mm. This signifies that the forecasting methodologies employed are dependable and possess significant implications as a reference for disaster prevention and mitigation efforts.
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Zhou, Fangrong, Xiaowei Huai, Pengcheng Yan, Cailing Zhao, Xingliang Jiang, Hao Pan, Yutang Ma und Hao Geng. „Research on the Identification of Typical Terrain Patterns in Yunnan Province Based on the K-Means Technology“. Atmosphere 15, Nr. 3 (20.02.2024): 244. http://dx.doi.org/10.3390/atmos15030244.
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Wire icing is a prevalent challenge in both industrial and scientific domains, and it is widely acknowledged that terrain and water vapor are significant contributing factors in the formation of wire icing. Consequently, the identification of terrains that are prone to inducing water vapor uplift serves as the scientific foundation for predicting ice accumulation on power lines. Yunnan Province, a mountainous province in China, features a large elevation difference. In winter, this region is prone to wire, pole and tower icing, which can affect power transmission and cause economic and property losses. Therefore, it is necessary to conduct research on the identification of typical terrain patterns in this region. In previous terrain studies, more attention has been focused on slope and aspect, watershed analysis and terrain profile analysis. When the purpose of the terrain identification is to analyze which terrains are more prone to collecting water vapor, we hope to obtain slightly larger terrain blocks and analyze the water vapor sources for different terrains in order to identify typical terrains that are conducive to icing formation. A new technology for identifying terrain patterns based on the K-means clustering method is proposed in this study to explore the typical terrain in Yunnan province. Additionally, the influences of different terrain patterns on water vapor movement are also analyzed. The results indicate that the typical terrains in Yunnan are “Valley-Air Channel”, “Topographic Uplifting”, “Ravine”, “Mountain Pass” and “Alpine Divide” patterns. The results show that the identified typical terrain is consistent with observations from satellite images, which verifies the effectiveness of this identification method. Among these five typical terrains, the “Valley-Air Channel”, the “Topographic Uplifting” and the “Mountain Pass” terrains are prone to collecting water vapor and forming ice cover. The “Alpine Divide” terrain is also prone to accumulating water vapor on both sides to form ice cover. The identified typical terrain demonstrates that typical terrain patterns near water bodies are more prone to the occurrence of wire, pole and tower icing because these areas are abundant in water vapor, and the extensive water vapor is easily condensed under the effects of terrain uplifting and cooling. In these key areas, existing wires and towers, as well as those to be constructed in the future, deserve our special attention.
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Li, Hui, Lin Chen, Zhaoyang Wang und Zhongdi Yu. „Mapping of River Terraces with Low-Cost UAS Based Structure-from-Motion Photogrammetry in a Complex Terrain Setting“. Remote Sensing 11, Nr. 4 (24.02.2019): 464. http://dx.doi.org/10.3390/rs11040464.
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River terraces are the principal geomorphic features for unraveling tectonics, sea level, and climate conditions during the evolutionary history of a river. The increasing availability of high-resolution topography data generated by low-cost Unmanned Aerial Systems (UAS) and modern photogrammetry offer an opportunity to identify and characterize these features. In this paper, we assessed the capabilities of UAS-based Structure-from-Motion (SfM) photogrammetry, coupled with a river terrace detection algorithm for mapping of river terraces over a 1.9 km2 valley of complex terrain setting, with a focus on the performance of this latest technology over such complex terrains. With the proposed image acquisition approach and SfM photogrammetry, we constructed a 3.8 cm resolution orthomosaic and digital surface model (DSM). The vertical accuracy of DSM was assessed against 196 independent checkpoints measured with a real-time kinematic (RTK) GPS. The results indicated that the root mean square error (RMSE) and mean absolute error (MAE) were 3.1 cm and 2.9 cm, respectively. These encouraging results suggest that this low-cost, logistically simple method can deliver high-quality terrain datasets even in the complex terrain, competitive with those obtained using more expensive laser scanning. A simple algorithm was then employed to detect river terraces from the generated DSM. The results showed that three levels of river terraces and a high-level floodplain were identified. Most of the detected river terraces were confirmed by field observations. Despite the highly erosive nature of fluvial systems, this work obtained good results, allowing fast analysis of fluvial valleys and their comparison. Overall, our results demonstrated that the low-cost UAS-based SfM technique could yield highly accurate ultrahigh-resolution topography data over complex terrain settings, making it particularly suitable for quick and cost-effective mapping of micro to medium-sized geomorphic features under such terrains in remote or poorly accessible areas. Methods discussed in this paper can also be applied to produce highly accurate digital terrain data over large spatial extents for some other places of complex terrains.
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Wiersema, David J., Katherine A. Lundquist und Fotini Katopodes Chow. „Mesoscale to Microscale Simulations over Complex Terrain with the Immersed Boundary Method in the Weather Research and Forecasting Model“. Monthly Weather Review 148, Nr. 2 (08.01.2020): 577–95. http://dx.doi.org/10.1175/mwr-d-19-0071.1.
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Abstract Improvements to the Weather Research and Forecasting (WRF) Model are made to enable multiscale simulations over highly complex terrain with dynamically downscaled boundary conditions from the mesoscale to the microscale. Over steep terrain, the WRF Model develops numerical errors that are due to grid deformation of the terrain-following coordinates. An alternative coordinate system, the immersed boundary method (IBM), has been implemented into WRF, allowing for simulations over highly complex terrain; however, the new coordinate system precluded nesting within mesoscale simulations using WRF’s native terrain-following coordinates. Here, the immersed boundary method and WRF’s grid-nesting framework are modified to seamlessly work together. This improved framework for the first time allows for large-eddy simulation over complex (urban) terrain with IBM to be nested within a typical mesoscale WRF simulation. Simulations of the Joint Urban 2003 field campaign in Oklahoma City, Oklahoma, are performed using a multiscale five-domain nested configuration, spanning horizontal grid resolutions from 6 km to 2 m. These are compared with microscale-only simulations with idealized lateral boundary conditions and with observations of wind speed/direction and SF6 concentrations from a controlled release from intensive observation period 3. The multiscale simulation, which is configured independent of local observations, shows similar model skill predicting wind speed/direction and improved skill predicting SF6 concentrations when compared with the idealized simulations, which require use of observations to set mean flow conditions. Use of this improved multiscale framework shows promise for enabling large-eddy simulation over highly complex terrain with dynamically downscaled boundary conditions from mesoscale models.
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ORDONEZ, JUAN, und CAMILO ORDONEZ. „ROBOTIC LEGS DESIGN – CONSTRUCTAL CONSIDERATIONS“. 14th CONSTRUCTAL LAW CONFERENCE | 10-11 October 2024, Bucharest, Romania 2024, Nr. 1 (18.12.2024): 109–12. https://doi.org/10.59277/clc.2024.28.
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In robotic navigation, wheels are highly efficient for engineered surfaces. However, they need to be more efficient when navigating over rough terrains. Evolution has resulted in limbed creatures that are highly adapted to extreme terrains. This paper explores the design of robotic legs for sagittal motion in uneven terrains. The paper builds upon locomotion theories to identify geometrical features of the leg and groups of legs as a function of terrain features. The predictions of the analytical models are compared against observations in the animal kingdom. The study is focused on legs that can be represented with two degrees of freedom, connected via revolute joints. It uses simplified terrain features and reduced-order dynamic models to evaluate the cost of transport associated with the different legs and terrain configurations. Examples of animal and animal-inspired robots to which the model applies include crabs, horses, and some insects. The model is expected to help design more agile robots and be extensible to designing human prostheses and end effectors for robotic manipulators.
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Liu, Peiting, Zhifang Xu, Jiandong Gong und Wei Chen. „A New Progressive EOFs Quality Control Method for Surface Pressure Data Based on the Barometric Height and Biweight Average Correction“. Atmosphere 14, Nr. 6 (15.06.2023): 1032. http://dx.doi.org/10.3390/atmos14061032.
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When assimilating surface pressure data in synoptic-scale models, we find the utilization rate of surface pressure data in zones with complex terrains is not high. Therefore, it is particularly important and urgent to carry out quality control of surface pressure data. Numerical weather prediction model analysis and forecasting provide essential data that can be compared with surface observations. The main adverse effects on surface pressure quality control include elevation differences between the model terrain and the observation stations and continuous outliers with the same characteristics in the initiation stage of quality control. Therefore, we propose a progressive empirical orthogonal function (EOF) with simulated observation (EOFs) combining barometric height correction (BHC) and biweight average correction (BAC) methods for the quality control of surface pressure data in this study. From the quality control results of the surface pressure data in regions with complex topography in China during June–August 2013, it was found that the BHC method could effectively reduce the deviations caused by elevation differences between the model terrain and the observation stations, and the BAC method could obviously reduce systematic deviations due to physical processes and the parameterization schemes of the models. The BHC-BAC method integrated the advantages of both methods and had the best correction effect. When continuous outliers with the same characteristics occurred in the initiation stage of quality control, the progressive EOF method might unreasonably eliminate observations. However, the progressive EOFs method could effectively solve this problem and had better performance in data quality control. The progressive EOFs quality control method with the combined BHC-BAC method could obviously reject outliers. The observation increment (deviations between observations and background field) after quality control by the progressive EOFs method was the closest to normal distribution, satisfying the Gaussian distribution assumption of data assimilation.
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Bieringer, Paul E., Peter S. Ray und Andrew J. Annunzio. „The Effect of Topographic Variability on Initial Condition Sensitivity of Low-Level Wind Forecasts. Part II: Experiments Using Real Terrain and Observations“. Monthly Weather Review 141, Nr. 7 (01.07.2013): 2156–72. http://dx.doi.org/10.1175/mwr-d-11-00055.1.
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Abstract A study by Bieringer et al., which is Part I of this two-part study, demonstrated analytically using the shallow-water equations and numerically in controlled experiments that the presence of terrain can result in an enhancement of sensitivities to initial condition adjustments. The increased impact of adjustments to initial conditions corresponds with gradients in the flow field induced by the presence of the terrain obstacle. In cross-barrier flow situations the impact of the initial condition adjustments on the final forecast increases linearly as the height of the terrain obstacle increases. While this property associated with initial condition perturbations may be present in an analytic and controlled numerical environment, it is often difficult to realize these benefits in a more operationally realistic setting. This study extends the prior work to a situation with actual terrain, Doppler radar wind observations over the terrain, and observations from a surface mesonet for model verification. The results indicate that the downstream surface wind forecast was improved more when the initial conditions adjusted through the assimilation of Doppler radar data originated from areas with terrain gradients than from regions where the terrain was relatively flat. This result is consistent with the findings presented in Part I and suggests that when varying terrain elevation is present upstream of a target forecast area, a greater benefit (in terms of forecast accuracy) can be made by targeting additional observations in the regions containing variable terrain than regions where the terrain is relatively flat.
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Carr, Michael H. „Mars Global Surveyor observations of Martian fretted terrain“. Journal of Geophysical Research: Planets 106, E10 (01.10.2001): 23571–93. http://dx.doi.org/10.1029/2000je001316.
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Grant, Eleanor R., Andrew N. Ross, Barry A. Gardiner und Stephen D. Mobbs. „Field Observations of Canopy Flows over Complex Terrain“. Boundary-Layer Meteorology 156, Nr. 2 (12.03.2015): 231–51. http://dx.doi.org/10.1007/s10546-015-0015-y.
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Lewis, H. W., S. D. Mobbs und M. Lehning. „Observations of cross‐ridge flows across steep terrain“. Quarterly Journal of the Royal Meteorological Society 134, Nr. 633 (April 2008): 801–16. http://dx.doi.org/10.1002/qj.259.
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Grant, A. L. M., und P. J. Mason. „Observations of boundary-layer structure over complex terrain“. Quarterly Journal of the Royal Meteorological Society 116, Nr. 491 (Januar 1990): 159–86. http://dx.doi.org/10.1002/qj.49711649107.
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Barkwith, A., und C. G. Collier. „Lidar observations of flow variability over complex terrain“. Meteorological Applications 18, Nr. 3 (22.08.2011): 372–82. http://dx.doi.org/10.1002/met.244.
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Bluestein, Howard B. „More Observations of Small Funnel Clouds and Other Tubular Clouds“. Monthly Weather Review 133, Nr. 12 (01.12.2005): 3714–20. http://dx.doi.org/10.1175/mwr3080.1.
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Abstract In this brief contribution, photographic documentation is provided of a variety of small, tubular-shaped clouds and of a small funnel cloud pendant from a convective cloud that appears to have been modified by flow over high-altitude mountains in northeast Colorado. These funnel clouds are contrasted with others that have been documented, including those pendant from high-based cumulus clouds in the plains of the United States. It is suggested that the mountain funnel cloud is unique in that flow over high terrain is probably responsible for its existence; other types of small funnel clouds are seen both over elevated, mountainous terrain and over flat terrain at lower elevations.
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Jiménez, Pedro A., und Jimy Dudhia. „On the Ability of the WRF Model to Reproduce the Surface Wind Direction over Complex Terrain“. Journal of Applied Meteorology and Climatology 52, Nr. 7 (Juli 2013): 1610–17. http://dx.doi.org/10.1175/jamc-d-12-0266.1.
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AbstractThe ability of the Weather Research and Forecasting (WRF) model to reproduce the surface wind direction over complex terrain is examined. A simulation spanning a winter season at a high horizontal resolution of 2 km is compared with wind direction records from a surface observational network located in the northeastern Iberian Peninsula. A previous evaluation has shown the ability of WRF to reproduce the wind speed over the region once the effects of the subgrid-scale topography are parameterized. Hence, the current investigation complements the previous findings, providing information about the model's ability to reproduce the direction of the surface flow. The differences between the observations and the model are quantified in terms of scores explicitly designed to handle the circular nature of the wind direction. Results show that the differences depend on the wind speed. The larger the wind speed is, the smaller are the wind direction differences. Areas with more complex terrain show larger systematic differences between model and observations; in these areas, a statistical correction is shown to help. The importance of the grid point selected for the comparison with observations is also analyzed. A careful selection is relevant to reducing comparative problems over complex terrain.
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Emeis, Stefan, Norbert Kalthoff, Bianca Adler, Eric Pardyjak, Alexandre Paci und Wolfgang Junkermann. „High-Resolution Observations of Transport and Exchange Processes in Mountainous Terrain“. Atmosphere 9, Nr. 12 (22.11.2018): 457. http://dx.doi.org/10.3390/atmos9120457.
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Mountainous areas require appropriate measurement strategies to cover the full spectrum of details concerning the energy exchange at the Earth’s surface and to capture the spatiotemporal distribution of atmospheric dynamic and thermodynamic fields over them. This includes the range from turbulence to mesoscale processes and its interaction. The surface energy balance needs appropriate measurement strategies as well. In this paper, we present an overview of important experiments performed over mountainous terrain and summarize the available techniques for flow and energy measurements in complex terrain. The description includes ground-based and airborne in situ observations as well as ground-based and airborne remote sensing (passive and active) observations. Emphasis is placed on systems which retrieve spatiotemporal information on mesoscale and smaller scales, fitting mountainous terrain research needs. Finally, we conclude with a short list summarizing challenges and gaps one faces when dealing with measurements over complex terrain.
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Jiménez, Pedro A., J. Fidel González-Rouco, Elena García-Bustamante, Jorge Navarro, Juan P. Montávez, Jordi Vilà-Guerau de Arellano, Jimy Dudhia und Antonio Muñoz-Roldan. „Surface Wind Regionalization over Complex Terrain: Evaluation and Analysis of a High-Resolution WRF Simulation“. Journal of Applied Meteorology and Climatology 49, Nr. 2 (01.02.2010): 268–87. http://dx.doi.org/10.1175/2009jamc2175.1.
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Abstract This study analyzes the daily-mean surface wind variability over an area characterized by complex topography through comparing observations and a 2-km-spatial-resolution simulation performed with the Weather Research and Forecasting (WRF) model for the period 1992–2005. The evaluation focuses on the performance of the simulation to reproduce the wind variability within subregions identified from observations over the 1999–2002 period in a previous study. By comparing with wind observations, the model results show the ability of the WRF dynamical downscaling over a region of complex terrain. The higher spatiotemporal resolution of the WRF simulation is used to evaluate the extent to which the length of the observational period and the limited spatial coverage of observations condition one’s understanding of the wind variability over the area. The subregions identified with the simulation during the 1992–2005 period are similar to those identified with observations (1999–2002). In addition, the reduced number of stations reasonably represents the spatial wind variability over the area. However, the analysis of the full spatial dimension simulated by the model suggests that observational coverage could be improved in some subregions. The approach adopted here can have a direct application to the design of observational networks.
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Wang, Yuhan, Jinsong Chen und Dawen Yang. „Bayesian Assimilation of Multiscale Precipitation Data and Sparse Ground Gauge Observations in Mountainous Areas“. Journal of Hydrometeorology 20, Nr. 8 (25.07.2019): 1473–94. http://dx.doi.org/10.1175/jhm-d-18-0218.1.
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Abstract Estimating the spatial distribution of precipitation is important for understanding ecohydrological processes at catchment scales. However, this estimation is difficult in mountainous areas because ground-based observation stations are often sparsely located and do not represent the spatial variability of precipitation. In this study, we develop a Bayesian assimilation method based on data collected on the Tibetan Plateau from 1980 to 2014 to estimate monthly and daily precipitation. To accomplish this, point-scale ground meteorological observations are combined with large-scale precipitation data such as satellite observations or reanalysis data. First, we remove the terrain effects from ground observations by fitting the precipitation data as functions of elevation, and then we spatially interpolate the residuals to 5-km-resolution grids to obtain monthly and daily precipitation. Additionally, we use Tropical Rainfall Measuring Mission (TRMM) satellite observations and ERA-Interim reanalysis data. Cross-validation methods are used to evaluate our method; the results show that our method not only captures the change in precipitation with terrain but also significantly reduces the associated uncertainty. The improvements are more evident in the main river source areas on the edge of the Tibetan Plateau, where elevation changes dramatically, and in high-altitude areas, where the ground gauges are sparse compared with those in low-altitude areas. Our assimilation method is applicable to other regions and is particularly useful for mountainous watersheds where ground meteorological stations are sparse and precipitation is considerably influenced by terrain.
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Meng hour, Ly. „Le phréatomagmatisme du plateau de Gergovie / The phreatomagmatism of Gergovie’s plateau“. Revue des sciences naturelles d'Auvergne 80, Nr. 1 (2016): 87–138. https://doi.org/10.3406/rsna.2016.1152.
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Le but de ce travail était initialement de produire une carte géologique du plateau de Gergovie, (zone de la carte Veyre-Monton N° 717, non encore éditée). En sus de la carte présentée ici, ce travail comporte un rapport de terrain illustré et commenté, ainsi qu’un repérage des affleurements et quatre coupes géologiques de synthèse. Cette étude est basée sur des observations de terrain réalisées entre 2012 et 2017. Le laboratoire Magmas et Volcans (LMV) et le Bureau de Recherches Géologiques et Minières (BRGM) ont réalisé des lames minces. Le présent document est un extrait réalisé pour la SHNA à partir du document original (Ly, 2017) ; il propose plusieurs circuits géologiques avec des descriptifs d’affleurements de terrains sédimentaires et volcaniques mettant en évidence le phréatomagmatisme de Gergovie.
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Lv, Y., X. H. Tong, S. J. Liu, H. Xie, K. F. Luan und J. Liu. „SIMULATION OF FULL-WAVEFORM LASER ALTIMETER ECHOWAVEFORM“. ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B1 (02.06.2016): 47–51. http://dx.doi.org/10.5194/isprsarchives-xli-b1-47-2016.
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Change of globe surface height is an important factor to study human living environment. The Geoscience Laser Altimeter System (GLAS) on ICESat is the first laser-ranging instrument for continuous global observations of the Earth. In order to have a comprehensive understanding of full-waveform laser altimeter, this study simulated the operating mode of ICESat and modeled different terrains’ (platform terrain, slope terrain, and artificial terrain) echo waveforms based on the radar equation. By changing the characteristics of the system and the targets, numerical echo waveforms can be achieved. Hereafter, we mainly discussed the factors affecting the amplitude and size (width) of the echoes. The experimental results implied that the slope of the terrain, backscattering coefficient and reflectivity, target height, target position in the footprint and area reacted with the pulse all can affect the energy distribution of the echo waveform and the receiving time. Finally, Gaussian decomposition is utilized to decompose the echo waveform. From the experiment, it can be noted that the factors which can affect the echo waveform and by this way we can know more about large footprint full-waveform satellite laser altimeter.
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Lv, Y., X. H. Tong, S. J. Liu, H. Xie, K. F. Luan und J. Liu. „SIMULATION OF FULL-WAVEFORM LASER ALTIMETER ECHOWAVEFORM“. ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B1 (02.06.2016): 47–51. http://dx.doi.org/10.5194/isprs-archives-xli-b1-47-2016.
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Change of globe surface height is an important factor to study human living environment. The Geoscience Laser Altimeter System (GLAS) on ICESat is the first laser-ranging instrument for continuous global observations of the Earth. In order to have a comprehensive understanding of full-waveform laser altimeter, this study simulated the operating mode of ICESat and modeled different terrains’ (platform terrain, slope terrain, and artificial terrain) echo waveforms based on the radar equation. By changing the characteristics of the system and the targets, numerical echo waveforms can be achieved. Hereafter, we mainly discussed the factors affecting the amplitude and size (width) of the echoes. The experimental results implied that the slope of the terrain, backscattering coefficient and reflectivity, target height, target position in the footprint and area reacted with the pulse all can affect the energy distribution of the echo waveform and the receiving time. Finally, Gaussian decomposition is utilized to decompose the echo waveform. From the experiment, it can be noted that the factors which can affect the echo waveform and by this way we can know more about large footprint full-waveform satellite laser altimeter.
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Bao, Jingyi, Fotini Katopodes Chow und Katherine A. Lundquist. „Large-Eddy Simulation over Complex Terrain Using an Improved Immersed Boundary Method in the Weather Research and Forecasting Model“. Monthly Weather Review 146, Nr. 9 (10.08.2018): 2781–97. http://dx.doi.org/10.1175/mwr-d-18-0067.1.
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Abstract The Weather Research and Forecasting (WRF) Model is increasingly being used for higher-resolution atmospheric simulations over complex terrain. With increased resolution, resolved terrain slopes become steeper, and the native terrain-following coordinates used in WRF result in numerical errors and instability. The immersed boundary method (IBM) uses a nonconformal grid with the terrain surface represented through interpolated forcing terms. Lundquist et al.’s WRF-IBM implementation eliminates the limitations of WRF’s terrain-following coordinate and was previously validated with a no-slip boundary condition for urban simulations and idealized terrain. This paper describes the implementation of a log-law boundary condition into WRF-IBM to extend its applicability to general atmospheric complex terrain simulations. The implementation of the improved WRF-IBM boundary condition is validated for neutral flow over flat terrain and the complex terrain cases of Askervein Hill, Scotland, and Bolund Hill, Denmark. First, comparisons are made to similarity theory and standard WRF results for the flat terrain case. Then, simulations of flow over the moderately sloped Askervein Hill are used to demonstrate agreement between the IBM and terrain-following WRF results, as well as agreement with observations. Finally, Bolund Hill simulations show that WRF-IBM can handle steep topography (standard WRF fails) and compares well to observations. Overall, the new WRF-IBM boundary condition shows improved performance, though the leeside representation of the flow can be potentially further improved.
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Xin, Yonghui, Ran Wang, Xi Wang, Xingwei Wang, Zhouxuan Xiao und Jingyu Lin. „High-Resolution Terrain Reconstruction of Slot Canyon Using Backpack Mobile Laser Scanning and UAV Photogrammetry“. Drones 6, Nr. 12 (19.12.2022): 429. http://dx.doi.org/10.3390/drones6120429.
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Accurate terrain models are critical for studying the formation and development of slot canyons. However, for slot canyon landforms, it is challenging to generate comprehensive and high-resolution morphological data by individual observation due to the inaccessibility of steep walls on either side and the complexity of the field observation environment, such as variable-slope terrain, partial vegetation cover, and lack of satellite signal. Off-the-shelf surveying techniques, including Unmanned Aerial Vehicles (UAV) photogrammetry and Backpack Mobile Laser Scanning (BMLS), facilitate slot canyon surveys and provide better observations. This paper proposes an integrated scheme to generate comprehensive and centimeter-resolution slot canyon terrain datasets (e.g., color point clouds, Digital Elevation Models (DEM), and 3D mesh) using BMLS and fine UAV photogrammetry. The results show that the fine flight of UAVs based on a rough model can avoid collision with obstacles or flying into restricted areas, allowing users to perform tasks faster and safer. Data integration of BMLS and UAV photogrammetry can obtain accurate terrain datasets with a Root Mean Squared Error (RMSE) of point cloud registration of 0.028 m. Such high-resolution integration terrain datasets reduce local data shadows produced solely by individual datasets, providing a starting point to revealing morphological evolution and genesis of slot canyons.
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Lundquist, Katherine A., Fotini Katopodes Chow und Julie K. Lundquist. „An Immersed Boundary Method Enabling Large-Eddy Simulations of Flow over Complex Terrain in the WRF Model“. Monthly Weather Review 140, Nr. 12 (01.12.2012): 3936–55. http://dx.doi.org/10.1175/mwr-d-11-00311.1.
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Abstract This paper describes a three-dimensional immersed boundary method (IBM) that facilitates the explicit resolution of complex terrain within the Weather Research and Forecasting (WRF) model. Two interpolation methods—trilinear and inverse distance weighting (IDW)—are used at the core of the IBM algorithm. This work expands on the previous two-dimensional IBM algorithm of Lundquist et al., which uses bilinear interpolation. Simulations of flow over a three-dimensional hill are performed with WRF’s native terrain-following coordinate and with both IB methods. Comparisons of flow fields from the three simulations show excellent agreement, indicating that both IB methods produce accurate results. IDW proves more adept at handling highly complex urban terrain, where the trilinear interpolation algorithm fails. This capability is demonstrated by using the IDW core to model flow in Oklahoma City, Oklahoma, from intensive observation period 3 (IOP3) of the Joint Urban 2003 field campaign. Flow in Oklahoma City is simulated concurrently with an outer domain with flat terrain using one-way nesting to generate a turbulent flow field. Results from the IBM-WRF simulation of IOP3 compare well with observations from the field campaign, as well as with results from an urban computational fluid dynamics code, Finite Element Model in 3-Dimensions and Massively Parallelized (FEM3MP), which used body-fitted coordinates. Using the FAC2 performance metric from Chang and Hanna, which is the fraction of predictions within a factor of 2 of observations, IBM-WRF achieves 100% and 71% for velocity predictions using cup and sonic anemometer observations, respectively. For the passive scalar, 53% of the model predictions meet the FAC5 (factor of 5) criteria.
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Feller, C., S. Fornasier, S. Ferrari, P. H. Hasselmann, A. Barucci, M. Massironi, J. D. P. Deshapriya et al. „Rosetta/OSIRIS observations of the 67P nucleus during the April 2016 flyby: high-resolution spectrophotometry“. Astronomy & Astrophysics 630 (20.09.2019): A9. http://dx.doi.org/10.1051/0004-6361/201833807.
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Context. From August 2014 to September 2016, the Rosetta spacecraft followed comet 67P/Churyumov–Gerasimenko along its orbit. After the comet passed perihelion, Rosetta performed a flyby manoeuvre over the Imhotep–Khepry transition in April 2016. The OSIRIS/Narrow-Angle-Camera (NAC) acquired 112 observations with mainly three broadband filters (centered at 480, 649, and 743 nm) at a resolution of up to 0.53 m/px and for phase angles between 0.095° and 62°. Aims. We have investigated the morphological and spectrophotometrical properties of this area using the OSIRIS/NAC high-resolution observations. Methods. We assembled the observations into coregistered color cubes. Using a 3D shape model, we produced the illumination conditions and georeference for each observation. We mapped the observations of the transition to investigate its geomorphology. Observations were photometrically corrected using the Lommel–Seeliger disk law. Spectrophotometric analyses were performed on the coregistered color cubes. These data were used to estimate the local phase reddening. Results. The Imhotep–Khepry transition hosts numerous and varied types of terrains and features. We observe an association between a feature’s nature, its reflectance, and its spectral slopes. Fine material deposits exhibit an average reflectance and spectral slope, while terrains with diamictons, consolidated material, degraded outcrops, or features such as somber boulders present a lower-than-average reflectance and higher-than-average spectral slope. Bright surfaces present here a spectral behavior consistent with terrains enriched in water-ice. We find a phase-reddening slope of 0.064 ± 0.001%/100 nm/° at 2.7 au outbound, similar to the one obtained at 2.3 au inbound during the February 2015 flyby. Conclusions. Identified as the source region of multiple jets and a host of water-ice material, the Imhotep–Khepry transition appeared in April 2016, close to the frost line, to further harbor several potential locations with exposed water-ice material among its numerous different morphological terrain units.
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Lin, Jung-Jun, und Chia-Hung Liang. „Terrain-based evaluation of groundwater potential and long-term monitoring at the catchment scale in Taiwan“. Advances in Geosciences 64 (26.07.2024): 13–17. http://dx.doi.org/10.5194/adgeo-64-13-2024.
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Abstract. In groundwater resource management, the hydrogeological framework significantly influences groundwater flow and storage. The complexity of groundwater systems in orogenic regions necessitates comprehensive investigations. To ensure sustainable groundwater management and address global climate change impacts, hydrogeological surveys and long-term monitoring at the catchment scale are essential. However, regional surveys are often limited by budget constraints and field accessibility. Therefore, integrating remote sensing and GIS technology to analyze terrain features, combined with field test results, facilitates the establishment of comprehensive terrain classifications and groundwater potential maps, aiding subsequent groundwater resource investigations and management. This study collected data from 75 field investigation sites spanning the mountainous to plain regions of central Taiwan at the catchment scale. The data included regolith thickness, hydraulic parameters, and nearly ten years of groundwater level observations. Terrain classifications were based on indices such as the topographic wetness index, topographic position index, and slope degree, resulting in seven distinct terrain types. The results revealed that in main riverbed deposits and flat slopes, there were higher average well yields and groundwater-level fluctuations. Greater fluctuations were observed in areas characterized by ridges, colluvium, and low elevation in slope areas and valleys. The variability in shallow aquifers was particularly pronounced, with outliers reaching higher levels in slope and valley terrains. These findings underscore the complexity of groundwater dynamics in diverse terrain types, highlighting the need for tailored management strategies to ensure sustainable groundwater resources.
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Xu, Anlun, und Jian Li. „An Overview of the Integrated Meteorological Observations in Complex Terrain Region at Dali National Climate Observatory, China“. Atmosphere 11, Nr. 3 (12.03.2020): 279. http://dx.doi.org/10.3390/atmos11030279.
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Systematically observing components of the climate system as well as their processes and interactions are crucial to understand the weather, climate, climate change, etc. In order to launch long-term, continuous, stereoscopic, and integrated meteorological observations for key regions of the climate system in southwestern China where it is sensitive to interactions among multiple layers and exchanges of mass and energy, the Dali National Climate Observatory (DNCO) was established in May 2006. To date, the DNCO has gradually performed an integrated meteorological observation network in a complex terrain region over the southeastern Tibetan Plateau including the conventional observations of weather and climate, and the special observations of radiation, lightning, soil moisture, wind profile, water vapor, water quality, water level, water temperature profile, turbulent fluxes of momentum, sensible heat, latent heat, carbon dioxide, and methane, etc. Furthermore, the DNCO mainly focuses on the field observation experiments and scientific research activities for mountain meteorology. This paper presents an overview of the DNCO including its location, climatology, scientific objectives, research tasks, and existing observation projects. The progresses in observation and associated research including data quality controls and assessments, recent observation results, and regional numerical model tests are summarized. Future works are also discussed.
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Elbing, Brian R., Trevor C. Wilson, Chris Petrin, Real J. KC, Taylor Swaim und Bryce B. Lindsey. „Tornado infrasound: Observations and potential mechanisms“. Journal of the Acoustical Society of America 153, Nr. 3_supplement (01.03.2023): A142. http://dx.doi.org/10.1121/10.0018441.
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Tornado warnings have not improved over the past 20 years, which is especially true in hilly terrain where radar cannot see near the ground due to the curvature of the earth. While Tornado Alley is best known for tornadoes, most tornado related deaths occur in the southeastern US where hilly terrain is more prevalent. Tornadoes emit sounds at frequencies below what humans can hear (infrasound), and there is strong evidence that these sounds carry information about the forming of the tornado as well as its size. In addition, these very low frequencies can travel well beyond the line-of-sight. Currently, this information is not used to guide warnings because we do not understand what makes it. Our team has been working on identifying the fluid mechanism for the past few years and there are four commonly proposed mechanisms that are consistent with observations; radial oscillation, latent heat effect, pressure relaxation, and shear instability. In this presentation each mechanism will be discussed relative to available observations. In addition, an overview of current field and laboratory testing motivated by the success and limitations of each proposed mechanism will be discussed.
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Zhou, Fan, Rongfan Li, Qiang Gao, Goce Trajcevski, Kunpeng Zhang und Ting Zhong. „Dynamic Manifold Learning for Land Deformation Forecasting“. Proceedings of the AAAI Conference on Artificial Intelligence 36, Nr. 4 (28.06.2022): 4725–33. http://dx.doi.org/10.1609/aaai.v36i4.20398.
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Landslides refer to occurrences of massive ground movements due to geological (and meteorological) factors, and can have disastrous impact on property, economy, and even lead to loss of life. The advances of remote sensing provide accurate and continuous terrain monitoring, enabling the study and analysis of land deformation which, in turn, can be used for possible landslides forecast. Prior studies either rely on independent observations for displacement prediction or model static land characteristics without considering the subtle interactions between different locations and the dynamic changes of the surface conditions. We present DyLand -- Dynamic Manifold Learning with Normalizing Flows for Land deformation prediction -- a novel framework for learning dynamic structures of terrain surface and improving the performance of land deformation prediction. DyLand models the spatial connections of InSAR measurements and estimates conditional distributions of deformations on the terrain manifold with a novel normalizing flow-based method. Instead of modeling the stable terrains, it incorporates surface permutations and captures the innate dynamics of the land surface while allowing for tractable likelihood estimates on the manifold. Our extensive evaluations on curated InSAR datasets from continuous monitoring of slopes prone to landslides show that DyLand outperforms existing bechmarking models.
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Grubišić, Vanda, und Mirko Orlić. „EARLY OBSERVATIONS OF ROTOR CLOUDS BY ANDRIJA MOHOROVIČIĆ“. Bulletin of the American Meteorological Society 88, Nr. 5 (01.05.2007): 693–700. http://dx.doi.org/10.1175/bams-88-5-693.
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This article delivers a short history of the early quantitative documentation of a rotor-type circulation in the bora-type flow on the northern Adriatic by Andrija Mohorovičić, an all-around geophysicist and the father of Croatian geophysical research who is widely known as the discoverer of discontinuity between the Earth's crust and mantle. This historical work presents an overview of Mohorovičić's research technique and rotor-related contributions, together with a short account of other observations of rotors contemporary to Mohorovičić as well as those from the 1920s and 1930s, considered to be seminal work on the subject on atmospheric rotors to date. In the year that marks the 150th anniversary of Mohorovičićs birth, his early meteorological observations remain germane for atmospheric rotor research, which is currently experiencing a renaissance with the Terrain-Induced Rotor Experiment (T-REX), a recently completed international field campaign and an ongoing research effort focused on atmospheric terrain-induced rotors.
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Griffith, Caitlin A., Juan M. Lora, Jake Turner, Paulo F. Penteado, Robert H. Brown, Martin G. Tomasko, Lyn Doose und Charles See. „Possible tropical lakes on Titan from observations of dark terrain“. Nature 486, Nr. 7402 (Juni 2012): 237–39. http://dx.doi.org/10.1038/nature11165.
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Kopp, Fred J., Paul L. Smith und Harold D. Orville. „On the Computation of Gradients from Observations over Complex Terrain“. Journal of Applied Meteorology 40, Nr. 10 (Oktober 2001): 1775–82. http://dx.doi.org/10.1175/1520-0450(2001)040<1775:otcogf>2.0.co;2.
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Neff, W. D. „Observations of complex terrain flows using acoustic sounders: Echo interpretation“. Boundary-Layer Meteorology 42, Nr. 3 (Februar 1988): 207–28. http://dx.doi.org/10.1007/bf00123813.
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Jindal, Abhinav S., Samuel P. D. Birch, Alexander G. Hayes, Orkan M. Umurhan, Raphael Marschall, Jason M. Soderblom, Jean-Baptiste Vincent und Dennis Bodewits. „Topographically Influenced Evolution of Large-scale Changes in Comet 67P/Churyumov–Gerasimenko's Imhotep Region“. Planetary Science Journal 3, Nr. 8 (01.08.2022): 193. http://dx.doi.org/10.3847/psj/ac7e48.
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Abstract Large portions of comet 67P/Churyumov–Gerasimenko’s northern hemisphere are blanketed by fallback material consisting of centimeter-sized particles termed the smooth terrains. Observations from the Rosetta mission show that the most drastic transient changes during 67P’s 2015 perihelion passage occurred within a subset of these deposits. However, we still do not understand the processes driving these changes, limiting our overall understanding of how comets evolve over both seasonal and multiorbit timescales. Herein we provide a complete documentation of scarp-driven activity on 67P’s largest smooth terrain deposit, a highly active portion of the Imhotep region that is the southernmost of all smooth terrain basins on 67P. We also present a thermal model that accurately predicts when and where scarps originate during the course of the observed activity. Assuming a uniform surface composition, our model shows that activity is heavily controlled by local topography rather than the presence of ice-enhanced hot spots on the surface. Scarps within the smooth terrain deposits in central Imhotep also exhibit a peculiar behavior, where three scarps originate from the same location but at different times and migrate in opposite directions. This behavior indicates that the landscape retains a memory of previous cycles of erosion and deposition, reflected by the depth of the volatile-rich layer. Future work will need to couple our thermal model with a landscape evolution model in order to explain the complete dynamic evolution of these terrains.
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Wang, Yansen, Christopher M. Hocut, Sebastian W. Hoch, Edward Creegan, Harindra J. S. Fernando, C. David Whiteman, Melvin Felton und Giap Huynh. „Triple Doppler wind lidar observations during the mountain terrain atmospheric modeling and observations field campaign“. Journal of Applied Remote Sensing 10, Nr. 2 (05.05.2016): 026015. http://dx.doi.org/10.1117/1.jrs.10.026015.
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Zhang, Yilin, Jiayu Zeng, Huimin Sun, Honglin Sun und Kenji Hashimoto. „Dual-Layer Reinforcement Learning for Quadruped Robot Locomotion and Speed Control in Complex Environments“. Applied Sciences 14, Nr. 19 (26.09.2024): 8697. http://dx.doi.org/10.3390/app14198697.
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Walking robots have been widely applied in complex terrains due to their good terrain adaptability and trafficability. However, in some environments (such as disaster relief, field navigation, etc.), although a single strategy can adapt to various environments, it is unable to strike a balance between speed and stability. Existing control schemes like model predictive control (MPC) and traditional incremental control can manage certain environments. However, they often cannot balance speed and stability well. These methods usually rely on a single strategy and lack adaptability for dynamic adjustment to different terrains. To address this limitation, this paper proposes an innovative double-layer reinforcement learning algorithm. This algorithm combines Deep Double Q-Network (DDQN) and Proximal Policy Optimization (PPO), leveraging their complementary strengths to achieve both fast adaptation and high stability in complex terrains. This algorithm utilizes terrain information and the robot’s state as observations, determines the walking speed command of the quadruped robot Unitree Go1 through DDQN, and dynamically adjusts the current walking speed in complex terrains based on the robot action control system of PPO. The speed command serves as a crucial link between the robot’s perception and movement, guiding how fast the robot should walk depending on the environment and its internal state. By using DDQN, the algorithm ensures that the robot can set an appropriate speed based on what it observes, such as changes in terrain or obstacles. PPO then executes this speed, allowing the robot to navigate in real time over difficult or uneven surfaces, ensuring smooth and stable movement. Then, the proposed model is verified in detail in Isaac Gym. Wecompare the distances walked by the robot using six different control methods within 10 s. The experimental results indicate that the method proposed in this paper demonstrates excellent speed adjustment ability in complex terrains. On the designed test route, the quadruped robot Unitree Go1 can not only maintain a high walking speed but also maintain a high degree of stability when switching between different terrains. Ouralgorithm helps the robot walk 25.5 m in 10 s, outperforming other methods.
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Varvayanni, Melpomeni, John G. Bartzis, Nicolas Catsaros, Panagiotis Deligiannis und Chuck E. Elderkin. „Simulation of Nocturnal Drainage Flows Enhanced by Deep Canyons: The Rocky Flats Case“. Journal of Applied Meteorology 36, Nr. 6 (01.06.1997): 775–91. http://dx.doi.org/10.1175/1520-0450-36.6.775.
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Abstract The DELTA–ADREA (discretization with elements of triangle approach–atmospheric dispersion of pollutants over irregular terrain) numerical prediction model, developed at the National Center for Scientific Research Demokritos, is specifically designed to perform wind field calculations over terrains of high complexity. The numerical model has the capability to handle air–ground interaction processes by describing the ground-surface details while keeping the computation time at a reasonable level. The numerical model is applied here to a high-resolution topographical representation of the region surrounding the Rocky Flats Facility in Colorado, based on a digitized map consisting of approximately 4.8 × 106 points. Wind field calculations over the region are made using the atmospheric experimental data of 4 February 1991, collected by the participants within the Atmospheric Studies in Complex Terrain research program. The numerical predictions indicate strong drainage flows created at different altitudes with interaction between them, resulting in a quite complicated mesoscale wind field during nighttime. Available observations support the predicted flow features.
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Sechaud, Mathieu. „Approche socio-ethnographique des processus de socialisation chez les adolescents d’une équipe de football amateur“. Revue internationale animation, territoires et pratiques socioculturelles, Nr. 13 (19.03.2018): 101–14. http://dx.doi.org/10.55765/atps.i13.265.
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Peu d’études socio-ethnographiques évoquent l’importance du football dans les processus de socialisation des jeunes. Cette recherche se veut résolument inductive et se base sur l’observation ethnographique du terrain de la Jeunesse Sportive Lafarge Limoges (JSL), un club de football d’un quartier de Limoges (Limousin). L’auteur souligne l’importance de l’esprit de compétition et de camaraderie, mais aussi l’émergence de préoccupations institutionnelles plus éducatives qui frappent ce milieu. L’analyse des observations de terrain a conduit à des sociologues de l’école de Chicago comme Berger et Luckmann, Goffman et Becker. Une observation plus attentive de ces rencontres quasi-quotidiennes entre joueurs, éducateurs et parents révèle ainsi des processus d’apprentissage et de socialisation plus complexes et réciproques entre les jeunes et le club.
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Gueye, ML, Y. Seye, ISS Sarr, PM Faye, M. Ndiaye, O. Thiam, AO Touré et al. „C45: Syndrome de Wilkie : A propos de 6 observations“. African Journal of Oncology 2, Nr. 1 Supplement (01.03.2022): S19—S20. http://dx.doi.org/10.54266/ajo.2.1s.c45.xszo1bitxc.
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INTRODUCTION : Le syndrome de la pince aorto-mésentérique ou syndrome de Wilkie est une entité rare. Il est défini par la compression de la troisième portion duodénale au niveau de l’angle formé par l'artère mésentérique supérieure et l'aorte abdominale. La tomodensitométrie permet de poser le diagnostic. Les étiologies sont variées et le traitement peut être conservateur ou chirurgical. Sa prise en charge ne doit souffrir d’aucun délai sous peine de grever le pronostic. Nous rapportons 6 cas de syndrome de Wilkie, d’étiologies et de pronostics divers. OBSERVATIONS : Il s’agissait de six patients, dont trois de sexe masculin ; l’âge moyen était de 34,2 ans. Le motif de consultation était un syndrome de sténose digestive haute (six). Les circonstances de survenue étaient une chirurgie d’arthrodèse du rachis pour une scoliose idiopathique à J3 post-opératoire (un) ; un amaigrissement récent important faisant suite à une gastroentérite sévère sur terrain diabétique (un) ; une toux vespéro-nocturne avec syndrome infectieux (deux) et un terrain d’anxiété avec anorexie (un) et une tumeur antro-pylorique (un cas). La TDM abdominale montrait dans tous les cas (six) : un angle aorto-mésentérique inférieur à 22 degrés. La distance aorto-mésentérique était également inférieure à huit mm dans les six cas. Trois patients avaient un taux de protidémie bas. Un traitement conservateur était instauré chez trois patients, avec la mise sous nutrition parentérale exclusive chez ces patients. L’évolution était marquée chez ces trois patients par une régression des symptômes (un), un décès (un) par probable syndrome de Mendelson, et une irritation péritonéale au 3ème jour de la nutrition parentérale, imposant une exploration chirurgicale (un). Celle-ci montrait une nécrose gastrique étendue sur un estomac hyper dilaté et une compression du D3. Chez les trois autres patients, l’indication chirurgicale était retenue d’emblée. Les gestes réalisés (trois) étaient : une duodéno-jéjunostomie trans-mésocolique sur D3 (un), une gastro-entéro-anastomose trans-mésocolique (un) et une gastrectomie totale avec anastomose œso-jéjunale (un). CONCLUSION : Le syndrome de Wilkie est une affection rare, qui se manifeste par un syndrome de sténose digestive haute. Un amaigrissement récent ou une chirurgie du rachis sont des terrains à rechercher systématiquement devant cette symptomatologie. Le traitement repose sur une nutrition parentérale, qui en cas d’échec, impose une chirurgie dans les meilleurs délais.
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Bieringer, Paul E., Peter S. Ray und Andrew J. Annunzio. „The Effect of Topographic Variability on Initial Condition Sensitivity of Low-Level Wind Forecasts. Part I: Experiments Using Idealized Terrain“. Monthly Weather Review 141, Nr. 7 (01.07.2013): 2137–55. http://dx.doi.org/10.1175/mwr-d-11-00054.1.
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Abstract The concept of improving the accuracy of numerical weather forecasts by targeting additional meteorological observations in areas where the initial condition error is suspected to grow rapidly has been the topic of numerous studies and field programs. The challenge faced by this approach is that it typically requires a costly observation system that can be quickly adapted to place instrumentation where needed. The present study examines whether the underlying terrain in a mesoscale model influences model initial condition sensitivity and if knowledge of the terrain and corresponding predominant flow patterns for a region can be used to direct the placement of instrumentation. This follows the same concept on which earlier targeted observation approaches were based, but eliminates the need for an observation system that needs to be continually reconfigured. Simulations from the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) and its adjoint are used to characterize the locations, variables, and magnitudes of initial condition perturbations that have the most significant impact on the surface wind forecast. This study examines a relatively simple case where an idealized mountain surrounded by a flat plain is located upwind of the forecast verification region. The results suggest that, when elevated terrain is present upstream of the target forecast area, the largest forecast impact (defined as the difference between the simulation with perturbed initial conditions and a control simulation where the initial condition was not perturbed) occurs when the initial analysis perturbations are made in regions with complex terrain.
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Burgess, M. M., und D. G. Harry. „Norman Wells pipeline permafrost and terrain monitoring: geothermal and geomorphic observations, 1984–1987“. Canadian Geotechnical Journal 27, Nr. 2 (01.04.1990): 233–44. http://dx.doi.org/10.1139/t90-027.
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A long-term permafrost and terrain research and monitoring program along the 869 km buried oil pipeline between Norman Wells, Northwest Territories, and Zama, Alberta, has been undertaken by the Geological Survey of Canada, in cooperation with the Department of Indian and Northern Affairs Canada. The two main program components are (1) the detailed quantification of changes in the geothermal regime and geomorphic conditions at instrumented monitoring sites and (2) general observations of terrain conditions and performance along the pipeline route. Pipeline operation commenced in April 1985. Observations during the first 2.5 years of pipeline operation indicate that, as expected, the pipe thermal regime and ground thermal regime have not yet stabilized in response to construction and operation. Warming trends in both mean annual pipe temperature and mean annual right-of-way ground temperature have occurred. Surface settlement in permafrost terrain is ongoing in the pipe trench as well as on the remainder of the right-of-way. Surface erosion has occurred, particularly at stream crossings and on low-angle slopes lacking erosion control structures. Key words: pipeline, permafrost, thermal regime, thaw settlement, surface erosion, instrumentation, Norman Wells, Mackenzie Valley, Canada.
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Ahijevych, D. A., C. A. Davis, R. E. Carbone und J. D. Tuttle. „Initiation of Precipitation Episodes Relative to Elevated Terrain“. Journal of the Atmospheric Sciences 61, Nr. 22 (01.11.2004): 2763–69. http://dx.doi.org/10.1175/jas3307.1.
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Abstract The western and central United States experience a pronounced diurnal cycle in rainfall during the warm season. Over the higher terrain west of 105°W, most precipitation occurs in the afternoon, whereas the central United States experiences more nocturnal events. This coherent phase transition between the Rocky Mountains and the U.S. Great Plains is well defined for all warm seasons between 1996 and 2003, provided that the rainfall observations are remapped relative to the elevated terrain in the western United States prior to north–south averaging. Due to the westward shift of the Continental Divide north of 42°N and its intersection with the warm season storm track for 2002, the diurnal coherence greatly improves after remapping the 2002 rainfall observations. This speaks to the long-range influence of orography on precipitation frequency and suggests that the primary east–west corridor of precipitation for an individual warm season intersects the cordillera over a fairly narrow latitude range.
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Gofa, Flora, Helena Flocas, Petroula Louka und Ioannis Samos. „A Coherent Approach to Evaluating Precipitation Forecasts over Complex Terrain“. Atmosphere 13, Nr. 8 (22.07.2022): 1164. http://dx.doi.org/10.3390/atmos13081164.
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Precipitation forecasts provided by high-resolution NWP models have a degree of realism that is very appealing to most users of meteorological data. However, it is a challenge to demonstrate whether or not such forecasts contain more skillful information than their lower resolution counterparts. A verification procedure must be based on equally detailed observations that are also realistic in areas where ground observations are not available and remote sensing data can only increase the accuracy of the location of rain events at the cost of decreased accuracy in estimating the amount of rain that has actually reached the ground. Traditional verification methods based on station or grid point comparison yield poor results for high-resolution fields due to the double penalty error that is attributed to finite space and time displacement that such methods do not account for. A complete approach to evaluating precipitation forecasts over complex terrain is suggested. The method is based on realistic gridded precipitation observations generated by an interpolation method that uses long climate data series to determine the geographical characteristics that this parameter is best correlated with as well as remote sensing estimates as background information to cover the areas where observations are insufficient. Spatial verification methodologies are subsequently applied to a convective event that accentuate the relative skill of high-resolution COSMOGR forecasts in revealing characteristics in the precipitation patterns such as structure and intensity.
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Arthur, Robert S., Katherine A. Lundquist, Jeffrey D. Mirocha und Fotini K. Chow. „Topographic Effects on Radiation in the WRF Model with the Immersed Boundary Method: Implementation, Validation, and Application to Complex Terrain“. Monthly Weather Review 146, Nr. 10 (18.09.2018): 3277–92. http://dx.doi.org/10.1175/mwr-d-18-0108.1.
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Abstract Topographic effects on radiation, including both topographic shading and slope effects, are included in the Weather Research and Forecasting (WRF) Model, and here they are made compatible with the immersed boundary method (IBM). IBM is an alternative method for representing complex terrain that reduces numerical errors over sloped terrain, thus extending the range of slopes that can be represented in WRF simulations. The implementation of topographic effects on radiation is validated by comparing land surface fluxes, as well as temperature and velocity fields, between idealized WRF simulations both with and without IBM. Following validation, the topographic shading implementation is tested in a semirealistic simulation of flow over Granite Mountain, Utah, where topographic shading is known to affect downslope flow development in the evening. The horizontal grid spacing is 50 m and the vertical grid spacing is approximately 8–27 m near the surface. Such a case would fail to run in WRF with its native terrain-following coordinates because of large local slope values reaching up to 55°. Good agreement is found between modeled surface energy budget components and observations from the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) program at a location on the east slope of Granite Mountain. In addition, the model captures large spatiotemporal inhomogeneities in the surface sensible heat flux that are important for the development of thermally driven flows over complex terrain.
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Wan, Mingfei, Daoguang Liu, Jun Wu, Li Li, Zhangjun Peng und Zhigui Liu. „State Estimation for Quadruped Robots on Non-Stationary Terrain via Invariant Extended Kalman Filter and Disturbance Observer“. Sensors 24, Nr. 22 (14.11.2024): 7290. http://dx.doi.org/10.3390/s24227290.
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Quadruped robots possess significant mobility in complex and uneven terrains due to their outstanding stability and flexibility, making them highly suitable in rescue missions, environmental monitoring, and smart agriculture. With the increasing use of quadruped robots in more demanding scenarios, ensuring accurate and stable state estimation in complex environments has become particularly important. Existing state estimation algorithms relying on multi-sensor fusion, such as those using IMU, LiDAR, and visual data, often face challenges on non-stationary terrains due to issues like foot-end slippage or unstable contact, leading to significant state drift. To tackle this problem, this paper introduces a state estimation algorithm that integrates an invariant extended Kalman filter (InEKF) with a disturbance observer, aiming to estimate the motion state of quadruped robots on non-stationary terrains. Firstly, foot-end slippage is modeled as a deviation in body velocity and explicitly included in the state equations, allowing for a more precise representation of how slippage affects the state. Secondly, the state update process integrates both foot-end velocity and position observations to improve the overall accuracy and comprehensiveness of the estimation. Lastly, a foot-end contact probability model, coupled with an adaptive covariance adjustment strategy, is employed to dynamically modulate the influence of the observations. These enhancements significantly improve the filter’s robustness and the accuracy of state estimation in non-stationary terrain scenarios. Experiments conducted with the Jueying Mini quadruped robot on various non-stationary terrains show that the enhanced InEKF method offers notable advantages over traditional filters in compensating for foot-end slippage and adapting to different terrains.
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Jia, Junru, Massimo Menenti, Li Jia, Qiting Chen und Anlun Xu. „Retrieval of At-Surface Upwelling Radiance and Albedo by Parameterizing Cloud Scattering and Transmittance over Rugged Terrain“. Remote Sensing 16, Nr. 10 (13.05.2024): 1723. http://dx.doi.org/10.3390/rs16101723.
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Accurate and continuous estimation of surface albedo is vital for assessing and understanding land–surface–atmosphere interactions. We developed a method for estimating instantaneous all-sky at-surface shortwave upwelling radiance and albedo over the Tibetan Plateau. The method accounts for the complex interplay of topography and atmospheric interactions and aims to mitigate the occurrence of data gaps. Employing an RTLSR-kernel-driven model, we retrieved surface shortwave albedo with a 1 km resolution, incorporating direct, isotropic diffuse; circumsolar diffuse; and surrounding terrain irradiance into the all-sky solar surface irradiance. The at-surface upwelling radiance and surface shortwave albedo estimates were in satisfactory agreement with ground observations at four stations in the Tibetan Plateau, with RMSE values of 56.5 W/m2 and 0.0422, 67.6 W/m2 and 0.0545, 98.6 W/m2 and 0.0992, and 78.0 98.6 W/m2 and 0.639. This comparison indicated an improved accuracy of at-surface upwelling radiance and surface albedo and significantly reduced data gaps. Valid observations increased substantially in comparison to the MCD43A2 data product, with the new method achieving an increase ranging from 40% to 200% at the four stations. Our study demonstrates that by integrating terrain, cloud properties, and radiative transfer modeling, the accuracy and completeness of retrieved surface albedo and radiance in complex terrains can be effectively improved.
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Ahrens, B. „Distance in spatial interpolation of daily rain gauge data“. Hydrology and Earth System Sciences Discussions 2, Nr. 5 (08.09.2005): 1893–922. http://dx.doi.org/10.5194/hessd-2-1893-2005.
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Abstract. Spatial interpolation of rain gauge data is important in forcing of hydrological simulations or evaluation of weather predictions, for example. The spatial density of available data sites is often changing with time. This paper investigates the application of statistical distance, like one minus common variance of time series, between data sites instead of geographical distance in interpolation. Here, as a typical representative of interpolation methods the inverse distance weighting interpolation is applied and the test data is daily precipitation observed in Austria. Choosing statistical distance instead of geographical distance in interpolation of an actually available coarse observation network yields more robust interpolation results at sites of a denser network with actually lacking observations. The performance enhancement is in or close to mountainous terrain. This has the potential to parsimoniously densify the currently available observation network. Additionally, the success further motivates search for conceptual rain-orography interaction models as components of spatial rain interpolation algorithms in mountainous terrain.
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Ahrens, B. „Distance in spatial interpolation of daily rain gauge data“. Hydrology and Earth System Sciences 10, Nr. 2 (04.04.2006): 197–208. http://dx.doi.org/10.5194/hess-10-197-2006.
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Abstract. Spatial interpolation of rain gauge data is important in forcing of hydrological simulations or evaluation of weather predictions, for example. This paper investigates the application of statistical distance, like one minus common variance of observation time series, between data sites instead of geographical distance in interpolation. Here, as a typical representative of interpolation methods the inverse distance weighting interpolation is applied and the test data is daily precipitation observed in Austria. Choosing statistical distance instead of geographical distance in interpolation of available coarse network observations to sites of a denser network, which is not reporting for the interpolation date, yields more robust interpolation results. The most distinct performance enhancement is in or close to mountainous terrain. Therefore, application of statistical distance in the inverse distance weighting interpolation or in similar methods can parsimoniously densify the currently available observation network. Additionally, the success further motivates search for conceptual rain-orography interaction models as components of spatial rain interpolation algorithms in mountainous terrain.
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Kim, Dong-Ju, Geon Kang, Do-Yong Kim und Jae-Jin Kim. „Characteristics of LDAPS-Predicted Surface Wind Speed and Temperature at Automated Weather Stations with Different Surrounding Land Cover and Topography in Korea“. Atmosphere 11, Nr. 11 (13.11.2020): 1224. http://dx.doi.org/10.3390/atmos11111224.
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We investigated the characteristics of surface wind speeds and temperatures predicted by the local data assimilation and prediction system (LDAPS) operated by the Korean Meteorological Administration. First, we classified automated weather stations (AWSs) into four categories (urban flat (Uf), rural flat (Rf), rural mountainous (Rm), and rural coastal (Rc) terrains) based on the surrounding land cover and topography, and selected 25 AWSs representing each category. Then we calculated the mean bias error of wind speed (WE) and temperature (TE) using AWS observations and LDAPS predictions for the 25 AWSs in each category for a period of 1 year (January–December 2015). We found that LDAPS overestimated wind speed (average WE = 1.26 m s−1) and underestimated temperature (average TE = −0.63 °C) at Uf AWSs located on flat terrain in urban areas because it failed to reflect the drag and local heating caused by buildings. At Rf, located on flat terrain in rural areas, LDAPS showed the best performance in predicting surface wind speed and temperature (average WE = 0.42 m s−1, average TE = 0.12 °C). In mountainous rural terrain (Rm), WE and TE were strongly correlated with differences between LDAPS and actual altitude. LDAPS underestimated (overestimated) wind speed (temperature) for LDAPS altitudes that were lower than actual altitude, and vice versa. In rural coastal terrain (Rc), LDAPS temperature predictions depended on whether the grid was on land or sea, whereas wind speed did not depend on grid location. LDAPS underestimated temperature at grid points on the sea, with smaller TE obtained for grid points on sea than on land.
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Hernandez-Joset, Alison, Virginie Nicaise und Natacha Chetcuti-Osorovitz. „Terrain de football, terrain de luttes : un nouvel espace de pratiques féministes, queer et sportives“. Nouvelles Questions Féministes Vol. 43, Nr. 1 (14.05.2024): 72–86. http://dx.doi.org/10.3917/nqf.431.0072.
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Depuis le début des années 2010, se multiplient en France des équipes de football se présentant comme féministes, lesbiennes et/ou queer. Les modalités organisationnelles de ces équipes sont proches de celles étudiées au sein des milieux féministes et queer mais peu communes dans le monde sportif. Ainsi, les équipes ne s’institutionnalisent pas auprès de la puissante Fédération française de football, mais préfèrent se développer au sein de l’espace sportif auto-organisé. De plus, elles se détachent de la non-mixité, norme dominante du monde sportif fédéral, en faisant de la mixité choisie un principe fondateur de leurs pratiques. À travers l’étude de cas d’une équipe, auprès de laquelle des observations et des entretiens ont été menés, l’article ambitionne de questionner les réflexions politiques de cet espace autour de l’institutionnalisation et de l’usage de la mixité choisie.
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Nakata, Makiko, Itaru Sano, Sonoyo Mukai und Alexander Kokhanovsky. „Characterization of Wildfire Smoke over Complex Terrain Using Satellite Observations, Ground-Based Observations, and Meteorological Models“. Remote Sensing 14, Nr. 10 (12.05.2022): 2344. http://dx.doi.org/10.3390/rs14102344.
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The severity of wildfires is increasing globally. In this study, we used data from the Global Change Observation Mission-Climate/Second-generation Global Imager (GCOM-C/SGLI) to characterize the biomass burning aerosols that are generated by large-scale wildfires. We used data from the September 2020 wildfires in western North America. The target area had a complex topography, comprising a basin among high mountains along a coastal region. The SGLI was essential for dealing with the complex topographical changes in terrain that we encountered, as it contains 19 polarization channels ranging from near ultraviolet (380 nm and 412 nm) to thermal infrared (red at 674 nm and near-infrared at 869 nm) and has a fine spatial resolution (1 km). The SGLI also proved to be efficient in the radiative transfer simulations of severe wildfires through the mutual use of polarization and radiance. We used a regional numerical model SCALE (Scalable Computing for Advanced Library and Environment) to account for variations in meteorological conditions and/or topography. Ground-based aerosol measurements in the target area were sourced from the National Aeronautics and Space Administration-Aerosol Robotic Network; currently, official satellite products typically do not provide the aerosol properties for very optically thick cases of wildfires. This paper used satellite observations, ground-based observations, and a meteorological model to define an algorithm for retrieving the aerosol properties caused by severe wildfire events.