Terrain Gradient Research Articles

Regional infrasonic observations from surface explosions – influence of atmospheric variations and realistic terrain

SUMMARY A pair of 1-ton, conventional surface explosions were conducted at the Nevada National Security Site in the fall of 2020 producing seismoacoustic signatures observable hundreds of kilometres from the source location. Regional infrasonic observations include tropospheric ducting at large distances to the south, a wide stratospheric waveguide with signals observed more than 700 km to the east, and anomalous arrivals in the stratospheric shadow zone. Notable differences in propagation between the events are identified despite the explosions being conducted just two days apart due to a sharp temporal shift in the tropospheric winds as well as structural changes in the stratospheric winds. Propagation simulations of the two events have been completed using a combination of ray tracing and parabolic equation (PE) methods. Simulations have been conducted to quantify the impact of the temporal variations in the atmosphere as well as the influence of terrain on propagation. Temporal variations in reflection locations are found to produce notable changes in downrange propagation due to spatially varying terrain features. Finite frequency effects modelled by the PE are found to predict ensonification not included in corresponding 2D ray tracing simulations. Notable variations in predicted signal amplitude are found due to focusing by along-path and cross-path terrain gradients; though, the later of these is only modelled using fully 3D ray tracing analysis.

Visuelle Kommunikation von Fahrradrouten mittels kartographischer Symbolisierung

ZusammenfassungMit zunehmender Förderung nachhaltiger Mobilitätsformen im Rahmen der Verkehrswende stellt das Fahrrad eine umweltfreundliche Alternative zum motorisierten Individualverkehr dar - insbesondere zur Bewältigung innerstädtischer Wege. Im Gegensatz zu Autofahrenden hängt der empfundene Fahrkomfort und das Sicherheitsempfinden von Radfahrenden jedoch stark von Routenmerkmalen wie der Oberflächenbeschaffenheit oder der Verkehrsinfrastruktur ab. Aktuell verfügbare Systeme zur Fahrradnavigation berücksichtigen diese für die Routenwahl von Radfahrenden relevanten Faktoren jedoch kaum und die Visualisierung beschränkt sich vielfach auf eine einfache Hervorhebung der empfohlenen Route. In dieser Arbeit wird daher untersucht, inwieweit sich verschiedene kartographische Darstellungsvarianten für Fahrradrouten zur visuellen Kommunikation der Routenmerkmale Art des Untergrunds, Untergrundrauigkeit, Geländeneigung und Fahrtunterbrechungen, als angemessen erweisen. Im Rahmen einer Nutzerbefragung wird die Effektivität, Attraktivität, Eignung und Entbehrlichkeit einer Legende der verschiedenen Darstellungsvarianten für die unterschiedlichen Routenmerkmale überprüft. Die Ergebnisse der Umfrage zeigen auf, dass viele der vorgeschlagenen Visualisierungsvarianten angemessen für die visuelle Kommunikation von Fahrradrouten sind. Dies betrifft insbesondere Farbdarstellungen sowie Darstellungen mit Symbolen oder Signaturen. Hinsichtlich der getesteten Fahrradroutenmerkmale hängt die angemessenste Darstellung jedoch stark von der zu kommunizierenden Information ab. Die Erkenntnisse dieser Studie sollen zur Entwicklung von speziell auf die Bedürfnisse der Radfahrenden zugeschnittenen Routenvisualisierungen beitragen und somit Entwicklern von Fahrradnavigationssystemen bei Designentscheidungen unterstützen.

Explicit Identification of Pointwise Terrain Gradients for Speed Compensation of Four Driving Tracks in Passively Articulated Tracked Mobile Robot

Tracked mobile robots can overcome the limitations of wheeled and legged robots in environments, such as construction and mining, but there are still significant challenges to be addressed in terms of trajectory tracking. This study proposes a kinematic strategy to improve the trajectory-tracking performance of a PASTRo (Passively Articulated Suspension based Track-typed mobile robot), which comprises four tracks, two rockers, a differential gear, and a main body. Due to the difficulties in explicitly identifying track-terrain contact angles, suspension kinematics is used to identify track-terrain contact angles (TTCA) in arbitrarily rough terrains. Thus, the TTCA-based driving velocity projection method is proposed in this study to improve the maneuverability of PASTRo in arbitrarily rough terrains. The RecurDyn-Simulink co-simulator is used to examine the improvement of PASTRo compared to a tracked mobile robot non-suspension version. The results indicate that PASTRo has a 33.3% lower RMS(Root Mean Square) distance error, 56.3% lower RMS directional error, and 43.2% lower RMS offset error than the four-track skid-steer mobile robot (SSMR), even with planar SSMR kinematics. To improve the maneuverability of PASTRo without any information on the rough terrain, the TTCA is calculated from the suspension kinematics, and the TTCA obtained is used for both TTCA-based driving velocity projection methods. The results show that PASTRo, with the TTCA-based driving velocity projection method, has a 39.2% lower RMS distance error, 57.9% lower RMS directional error, and 51.9% lower RMS offset error than the four-track SSMR.

Distribution and change of China’s population on the terrain gradients from 2000 to 2020

Distribution and change of China’s population on the terrain gradients from 2000 to 2020

Terrain gradient response of landscape ecological environment to land use and land cover change in the hilly watershed in South China

There are abundant resources like climate, water, biological and tourism in the middle and upper reaches of the Ganjiang River (MU-GJR), which is an important ecological protection area in hilly areas of South China. The four periods of land use and land cover (LULC) data from 1980 to 2018 and DEM data are the main data support. The LULC change were analyzed with the area proportion, transfers chord diagram and change characteristics map, the response of ecological environment from LULC change was analyzed by using the landscape ecological environment quality (LEEQ) and contribution index. Then the terrain gradient was used to analyze the impact of LULC transfer on ecological environment under different terrain conditions. (1) The LULC characteristics in the study area show that was dominated by forest land and cultivated land (more than 90 %), various types of land transfer significantly from 2010 to 2018, especially the cultivated land, forest land and grassland. The stable type of LULC change was the most widely distributed, followed by the later change type (2010–2018) and mainly distributed in the flat valley, with the largest change range of cultivated land, forest land and grassland. (2) The LEEQ was generally well, but gradually deteriorates. The obvious change of LEEQ was found after 2010. The deterioration type of quality mostly occurs around the city, while the getting better type occurs in the transition area between the city and the mountains. (3) There are more deterioration categories than improvement categories of LULC transfer from 1980 to 2018. The improvement categories were mainly contributed by the transfer to other land to forest land and build-up land to other land. The deterioration categories were mainly contributed by the transfer of forest land to other land. (4) The impact of LULC change on the ecological environment decreases with the increase of elevation, slope and terrain position. There are differences in the impacts of various types of transfer on the ecological environment under the three gradients. In the elevation gradient, the improvement effect were dominant at −105–100 m and 200–500 m, and the deterioration effect were dominant at 100–200 m, 500–1000 m and 1000–2128 m. In the slope gradient, the improvement effect were dominant at 0–2°, 15–25° and 25–69.7°, and the deterioration effect were dominant at 2–6° and 6–15°. In terrain position gradient, improvement effect were dominant at 0–0.32, 0.32–0.51, 0.7–0.9 and 0.9–1.58, and deterioration effect were dominant at 0.51–0.7. Therefore, the specific conditions of different terrain gradients should be considered for land resource development in the middle and upper reaches of Ganjiang River region.

Uncommonly known change characteristics of land use pattern in Guangdong Province–Hong Kong–Macao, China: Space time pattern, terrain gradient effects and policy implication

Previous studies on land use have largely focused on characteristics of quota allocation and spatial distribution based on time series analysis. However, indwelling patterns, combined space–time characteristics and terrain gradient effects are often hidden from the regional territorial spatial planning process. By using spatial econometric techniques, including hot spot analysis, landscape theory, a space–time cube model and a terrain–niche index, this paper aimed to assist regional planning by revealing these hidden characteristics in Guangdong Province, China. The results were as follows: urban construction land had formed an agglomerated region at the center of the study area, surrounded by many smaller satellite cities, which resembled a mainland–island metapopulation pattern. Three hot spot types—oscillating (32.45 % of the region), sporadic (1.85 %) and persistent (6.83 %)—formed the main space–time pattern throughout the study period. The main patterns included persistent hot spots in the Pearl River Delta, approximating a strip pattern of sporadic and oscillating hot spots from the east to west, with persistent cold spots in the north. Dry land cropping showed an increase in area at terrain levels 3–6 while in other terrains the area of dry land cropping decreased over time. These findings indicate that more attention needs to be paid to maintaining or adjusting the shape and equilibrium between the mainland and the island cities in the future. Steeper terrain is normally considered for cropland when conflicts exist for land use, which might decrease cropland quality to some extent. Hence, current territorial and spatial planning should focus on changing spatial disequilibrium and the reduction in cropland quality, which might result from the land policy of “superior occupation and inferior compensation”, to slow regional differences and to achieve sustainable development.

Spatial Response of Ecosystem Service Value to Urbanization in Fragile Vegetation Areas Based on Terrain Gradient.

The contradiction between urban expansion and ecological protection in fragile vegetation areas has become increasingly prominent with regional development. Revealing the relationship between urbanization and ecosystem services will help to provide solutions to this problem. In order to clarify the impact of urbanization on typical mountain areas with fragile vegetation on the Qinghai Tibet Plateau, we built an ecosystem service value (ESV) evaluation index system. We also evaluated the ESV and its spatial response to the urbanization of Shannan Prefecture in Tibet from 1990 to 2015 based on different terrain gradients (TGs) using vegetation biophysical data obtained from remote sensing platforms. The results show that ESV in Shannan increased first and then declined as the TG increased, reaching a maximum value at the third TG. ESV showed a decreased trend during the study period, with a significant decline at the second and third TGs, which were the main distribution areas of vegetation in Shannan. Through spatial correlation analysis, we observed that urbanization and ESV showed a significant spatial aggregation effect. Among them, the high-low type accounted for the largest proportion in the grid with the agglomeration effect, mainly concentrated at the lower TG in the southern of Shannan, where ESV decreases with the increasing urbanization. We highlight the need for targeted, sustainable development policies to rationally organize the urbanization process in the different-gradient plateau regions with fragile vegetation. These results can provide a reference for applying ESV to vegetation restoration and ecological protection in ecologically fragile mountain areas.

Multi-Scenario Prediction of Landscape Ecological Risk in the Sichuan-Yunnan Ecological Barrier Based on Terrain Gradients

Land use changes induced by human activities change landscape patterns and ecological processes, threatening regional and global ecosystems. Terrain gradient and anthropogenic multi-policy regulation can have a pronounced effect on landscape components. Forecasting the changing trend of landscape ecological risk (LER) is important for national ecological security and regional sustainability. The present study assessed changes in LER in the Sichuan-Yunnan Ecological Barrier over a 20-year period using land use data from 2000, 2010, and 2020. The enhanced Markov-PLUS (patch-generating land use simulation) model was used to predict and analyze the spatial distribution pattern of LER under the following three scenarios. These were business-as-usual (BAU), urban development and construction (UDC), and ecological development priority (EDP) in 2030. The influence of terrain conditions on LER was also explored. The results showed that over the past 20 years, the LER index increased and then decreased and was dominated by medium and low risk, accounting for more than 70% of the total risk-rated area. The highest and higher risk areas for the three future scenarios have increased in spatial extent. The UDC scenario showed the largest increase of 3341.13 km2 and 2684.85 km2, respectively. The highest-risk level has a strong selectivity for low gradients, with high-level risks more likely to occur at low gradients. The response of ecological risk to gradient changes shows a positive correlation distribution for high-gradient areas and a negative correlation distribution for low-gradient areas. The influence of future topographic gradient changes on LER remains significant. The value of multiscale geographically weighted regression (MGWR) for identifying the spatial heterogeneity of terrain gradient and LER is highlighted. It can play an important role in the formulation of scientific solutions for LER prevention and of an ecological conservation policy for mountainous areas with complex terrain.

Spatial identification and multilevel zoning of land use functions improve sustainable regional management: a case study of the Yangtze River Economic Belt, China.

The quantitative identification and zoning management of land use functions (LUFs) are important starting points for solving the problems of resource allocation and sustainable development. In this study, with the Yangtze River Economic Belt (YREB) as the case study area, LUFs were grouped into three primary categories: economic function (ENF), social function (SCF), and ecological function (ELF). The least square error model was adopted to identify the morphological changes of LUFs. A two-dimensional discriminant matrix of the dynamic degree of LUF change and terrain niche index was constructed to explain the terrain gradient effect of LUFs. Bivariate local spatial autocorrelation was used to analyze the trade-offs in 2018 between ELF and ENF, and ELF and SCF. Finally, a new multilevel zoning scheme for LUFs was proposed. The results showed that from 1990 to 2018, ENF increased rapidly in cities along the Yangtze River, the overall level of SCF declined, and ELF in the south of the Yangtze River was better than that in the north. LUFs' morphological zoning exhibited significant regional differences. SCF-ELF combination areas and ELF dominance areas were mainly optimized in the second-level zoning. The areas with weak ELF were concentrated in the east of the YREB. Based on these results, nine kinds of LUF zonings and six kinds of major functional zonings were devised, and policy allocation was arranged for each zoning to improve the efficiency of spatial zoning management. Our research provides a reference for large-scale regional sustainable development and land use zoning management.

Analysis of the effect of slope on the power characteristics of wind turbines in hillside terrain

As a kind of clean and renewable energy, wind power has a wide development prospect. The aerodynamic performance and power generation efficiency of wind turbines are influenced by the gradient of wind turbine installation terrain. In this paper, the 5 MW wind turbine is taken as the object, and the influence characteristics of slope of hillside terrain on the power of wind turbine are studied through the simulation software STAR CCM+, and the influence characteristics of slope of hillside terrain on the power characteristics of wind turbine are obtained. The results show that when the wind turbine is installed on the top platform of the slope, the power of the wind turbine increases first and then decreases with the increase of the slope, power increased by 16.3% when the slope increased from 15 degrees to 52 degrees, decreased by 22.6% when the slope increased from 52 degrees to 60 degrees and reaches the peak value when the slope is about 52°. The appropriate slope can play a positive role in improving the power generation efficiency of the wind turbine. When the wind turbine is installed at the bottom of the slope, the slope will have an obstruction effect on the incoming flow velocity of the wind turbine, and the obstruction effect becomes more obvious with the increase of the slope, As the slope increased from 15 degrees to 45 degrees, power decreased by 6.7%, thus reducing the power generation efficiency of the wind turbine. Therefore, the influence of the slope on the aerodynamic performance of the wind turbine should be considered in the installation of the wind turbine. This study reveals the influence characteristics of terrain slope on wind turbine power characteristics, and provides a theoretical reference for making full use of terrain advantages to arrange wind turbines reasonably.

Reveal the severe spatial and temporal patterns of abandoned cropland in China over the past 30 years

The abandonment phenomenon is familiar in China. It threatens food security and seriously affects the sustainable development of society, the economy, and the natural environment. However, monitoring and mapping abandoned cropland on a large scale remains a challenge because of its complex land-use change process. According to the World Food and Agriculture Organization, cropland not used for agricultural production for more than 5 years is defined as abandoned cropland. This study uses the Landsat high-precision long-time series product to detect cropland nationwide from 1990 to 2019 by using the sliding window method on Google Earth Engine to profile the spatial distribution, intensity, trend, frequency, and recultivation of abandoned cropland. Between 1992 and 2015, the results illustrate that the total area of abandoned cropland in China was 559,170.26 km2, 18.59 % of the cropland area. Excluding the recultivated cropland area, China's abandoned cropland area amounted to 392,156.24 km2, 13.03 % of the total cropland. Cropland abandonment is mainly distributed in the second terrain gradient in midwestern and southwestern regions such as Inner Mongolia and Gansu. It rarely happens in western and eastern coastal areas. A high abandonment rate area usually has high elevation and slope. The light index is negatively correlated with the abandonment rate in suburban areas. This study is the first to map the spatiotemporal distribution of abandoned cropland in China with high precision at 30 m resolution. It provides an important basis for policies regarding the recultivation of abandoned cropland.

Monitoring the Spatiotemporal Dynamics of Habitat Quality and Its Driving Factors Based on the Coupled NDVI-InVEST Model: A Case Study from the Tianshan Mountains in Xinjiang, China

Globally, mountains have suffered enormous biodiversity loss and habitat degradation due to climate change and human activities. As an agent of biodiversity, evaluating habitat quality (HQ) change is an indispensable key step for regional ecological security and human well-being enhancement, especially for fragile mountain ecosystems in arid areas. In this study, we aimed to propose an integrated framework coupled with the Normalized Difference Vegetation Index (NDVI) and Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST)-HQ module to improve the effectiveness and accuracy of HQ estimation. We highlighted the Tianshan Mountains in Xinjiang as an example to validate the model, as it is a typical representative of mountain ecosystems in the temperate arid zone. Specifically, we aimed to assess the spatiotemporal dynamics of HQ over the past two decades and investigate its influencing factors using a geographical detector model. The results show that, first, grassland and unused land were the main land-use types in the study area. The land-use transitions were mainly concentrated in grassland, woodland, water body, and unused land. Second, the total area of very important habitats and general habitats accounted for over 70% of the Tianshan Mountains. The average HQ decreased from 0.5044 to 0.4802 during 1995–2015. Third, the HQ exhibited significant spatial differentiation, and the Ili River Valley and Kaidu River Basin were the hot spots, while the south and east of the Tianshan Mountains were the cold spots. Habitat quality was strongly related to the terrain gradient, with an inverted “U” type. Protected areas of different categories played a vital role in biodiversity conservation. Finally, soil type, land-use change, precipitation, temperature, and grazing intensity were the dominant factors in response to HQ change for both the total Tianshan Mountains and sub-regions, followed by elevation, the relief degree of the land surface, gross domestic product, population density, and distance to tourism attractions. The interaction effects of the influencing factors were improved compared to the effects of the individual factors in each zone. Furthermore, these results provide decision-making criteria for formulating a scientific and systematic protection of ecology and restoration planning systems to enhance the capacity to address climate change.

How Rough Is the Path? Terrain Traversability Estimation for Local and Global Path Planning

Perception and interpretation of the terrain is essential for robot navigation, particularly in off-road areas, where terrain characteristics can be highly variable. When planning a path, features such as the terrain gradient and roughness should be considered, and they can jointly represent the traversability cost of the terrain. Despite this range of contributing factors, most cost maps are currently binary in nature, solely indicating traversible versus non-traversible areas. This work presents a joint local and global planning methodology for building continuous cost maps using LIDAR, based on a novel traversability representation of the environment. We investigate two approaches. The first, a statistical approach, computes terrain cost directly from the point cloud. The second, a learning-based approach, predicts an IMU response solely from geometric point cloud data using a 2D-Convolutional-LSTM neural network. This allows us to estimate the cost of a patch without directly driving over it, based on a data set that maps IMU signals to point cloud patches. Based on the terrain analysis, two continuous cost maps are generated to jointly select the optimal path considering distance and traversability cost for local navigation. We present a real-time terrain analysis strategy applicable for local planning, and furthermore demonstrate the straightforward application of the same approach in batch mode for global planning. Off-road autonomous driving experiments in a large and hybrid site illustrate the applicability of the method. We have made the code available online for users to test the method.

The Spatial Features and Driving Mechanism of Homestead Agglomeration in the Mountainous and Hilly Areas of Southwestern China: An Empirical Study of 22 Villages in Chongqing

Scientific analysis of the spatial features and driving factors of homestead agglomeration in different landform types of mountainous and hilly areas in Southwest China is of great significance for the optimization of national spatial patterns and high-quality rural development. This paper selects 22 villages in 3 towns with different landform types in Chongqing and examines the spatial features and driving factors of homestead agglomeration in different landform types from the perspectives of terrain gradient, kernel density estimation, farmer household agglomeration status, and landscape index. We analyzed the agglomeration spatial features of different landform types and explored their driving factors and mechanisms. It was found that (1) the distribution of homesteads in mountainous and hilly areas has obvious terrain gradient characteristics, and the layout of platform area homesteads is not constrained by terrain conditions. (2) Chongqing homesteads show a spatially dispersed pattern, but the degree of homestead spatial agglomeration varies significantly among different landform types, with those in mountainous and hilly areas being mainly dispersed and those in platform areas being mainly clustered. (3) Homestead spatial agglomeration is characterized by a combination of factors inside and outside the rural system and farmers’ willingness. There are differences in the driving factors of homestead agglomeration in different landform types. Homestead agglomeration in mountainous and hilly areas is mainly driven externally, while homestead agglomeration in platform areas is mainly driven internally. In both situations, farmers’ willingness must be fully considered. The results of this study can provide a scientific basis for the spatial planning and optimal allocation of land resources in the southwestern hilly area.

Assessing the Terrain Gradient Effect of Landscape Ecological Risk in the Dianchi Lake Basin of China Using Geo-Information Tupu Method.

The assessment of landscape ecological risk (LER) in different terrain gradients is beneficial to ecological environmental protection and risk management in different terrain gradients. Due to the impact of urban expansion, the landscape pattern of the Dianchi Lake basin (DLB) changed obviously, resulting in significant spatial difference of LER. At present, the LER assessment of the DLB is not clear, and the evolution mechanism of LER in different terrain gradients has not been revealed. Based on the LER assessment model, the geo-information Tupu method, the terrain niche gradient, and distribution index, this paper analyzed the LER and its terrain gradient effect in the DLB of China. The conclusions are as follows: (1) Since 1995, the land use type has mainly changed from grassland and cultivated land to construction land in the DLB of China. (2) The LERs in the DLB of China were mainly low, med low, and med high due to the transformation of land use type. The dominance distribution of the low and high LER was obviously constrained by terrain gradient. While the dominance distribution of med-low LER expanded to med-high terrain gradient, the dominance distribution of the med-high LER decreased to med-low terrain gradient. (3) The Tupu LERs were mainly a stable type of “medium” risk and anaphase change type of “med-high to medium” risk. The dominant distribution regions of the stable type, the prophase change type, and the continuous change type were relatively stable; the anaphase and middle change type expanded to the higher terrain gradient, and the repeated change type decreased to the med-high terrain gradient. In the process of ecological risk management and protection in the DLB, attention should be paid to the water area structure and LER control in med-high and high terrain gradients.

The Influence of a Cold Front and Topography on the Initiation and Maintenance of a Precipitation Convective System in North China: A Case Study.

By using the convection-resolving weather research and forecasting simulation, a convective rainfall event over the middle portions of the eastern foothills of the Taihang Mountains in North China is investigated in this study. The influences of the cold front and complex topography on the initiation and maintenance of the convective system are analyzed. Results show two reasons why the convective clusters are initiated near noon on the hillsides at an elevation of 800 m. First, a local topographic convergence zone usually appears on the eastern slope of the Taihang Mountains near noon in May. Second, such a topographic convergence zone is enhanced by a cold front system and then triggers the convective clusters. Subsequently, the convective cells strengthen when moving downslope and weaken when moving eastward on the plain. When moving downslope, the atmospheric stratification is convectively unstable, and the mountain–plains solenoid (MPS) is strong near the foot of the mountain. The large amount of water vapor carried by the MPS-induced easterly wind is forced to ascend by topographic obstructions, and therefore the convective cells develop. As a result, heavy rainfall occurs on the hillsides with an elevation of 200–600 m. When the convective cells move eastward on the plain, the atmospheric stratification is stable, and the MPS is weak. Thus, convective activities weaken. Moreover, the results reveal that the mesoscale convergence line, slope gradient and slope aspect of the local terrain, local atmospheric instability, and the MPS play different roles in maintaining the convective system at elevations of 200–600 m along the eastern foothills of the Taihang Mountains.

Efficient and multifidelity terrain modeling for 3D large‐scale and unstructured environments

AbstractThe vast amount of data captured by robots in large‐scale unstructured environments brings computation and storage problems to terrain modeling methods. Considering the practical terrain geometry structures, we design a large‐scale terrain modeling framework for efficiently generating the compact and accurate terrain models from incomplete and uncertain measurements. The multiresolution elevation filtering is developed to generate terrain surfaces that preserve terrain details in the bumpy areas while achieving a sparse representation over the flat areas, which simultaneously reduces the computation time, storage space, and inference error. To further reduce the high computational complexity, we propose a computation decomposition strategy by adopting the Gaussian mixture model to partition the whole terrain surface into several subsurfaces, enabling the method to scale to much larger environments. For each subsurface, we train a Gaussian process model using the local data to adapt to the local terrain structure, concurrently resolving the data incompleteness and uncertainty. Furthermore, to provide a more informative terrain model, we efficiently derive terrain gradient through a closed‐form solution by treating the generated terrain models as continuous functions, enabling more robotics applications, such as the path planning. We perform extensive experiments to evaluate our framework, including the use of two medium‐sized terrain data sets to evaluate the overall and local performance, and two large‐scale glacier terrain and mountain terrain in the area of up to 9 km2 to validate the practical applications.

How urbanization affect the ecosystem health of Tibet based on terrain gradients: a case study of Shannan, China

ABSTRACT Urbanization has significant impacts on ecosystem health (ESH) by affecting land-use patterns. The evaluation of the ESH and the spatial correlations between human interference provides an insight into sustainable development as a response to potential ecological degradation if ESH is threatened by further urbanization. We applied the Vigor-Organization-Resilience-Services (VORS) modelto detect the responses of ESH of Shannan Prefecture in the Tibet to urbanization from 1990 to 2015, based on different levels of terrain gradients. The results show that the ESH of the most areas in Shannan reaches the levels of highest health and average health during the study period. By 2015, the area proportion at the highest health level increased by 0.68%, while that of degraded level decreased by 1.51%. Overall, the ESH of areas tends to shrink at higher-level TGs, and urban sprawl with ESH shrinking existed in middle-level TGs in Shannan. Furthermore, a significant spatial aggregation effect was found concerning that low ESH–high CUL type is mainly distributed on the middle-level TGs with dense human population. The results highlight the needs to rationally organize urbanization process in plateau regions based on different TGs, which contribute to maintain ESH advancing people livelihood improvement.

Analyzing the characteristics of land use distribution in typical village transects at Chinese Loess Plateau based on topographical factors

Abstract The spatial distribution of land use at different terrain gradients has been used as an important index for the land management and ecological restoration in the Loess Plateau of China. Based on the land use data surveyed in 2015 and digital elevation model data with a resolution of 30 m from typical village transects in the Loess Plateau area in Yan’an City, Shaanxi Province, this study analyzed the terrain niche index, distribution index, land utilization comprehensive index, and land use equilibrium degree for four village transects. The results demonstrated that the land use types in the four village transects were mainly grassland, forest land, and cropland. Land use types showed obvious differences in respect to topographical gradient with built-up land, traffic land, water bodies, cropland, and orchard distributed in low terrain gradient areas, forest land, and grassland distributed in medium- and high-terrain areas. As terrain gradient increased, the land utilization comprehensive index and land use equilibrium degree showed a generally decreasing trend. These findings may provide a useful reference for land use planning and land resource allocation in the Loess Plateau region.

Dynamical and thermodynamical interactions in daily precipitation regimes in the Western Himalayas

AbstractThe mechanisms by which moisture interacts with the Himalayas largely determine the amount of precipitation in Himalayan basins. While many recent studies have focused on mechanisms of independent precipitation events, climatological studies that are essential for a complete understanding of precipitation‐generating mechanisms are limited. This work presents synoptic regimes, which produced precipitation across all seasons in the Western Himalayas (WH) from 2000 to 2018. Using the k‐means clustering algorithm, seven clusters are employed to define relatively mild, moderate and wet regimes, showing distinct seasonality and a synoptic meteorology. We found positive precipitation anomalies at lower elevations in monsoonal regimes (M1, M2 and M3) but at higher elevations in winter (W1 and W2) and transitional regimes (T1 and T2). Moist monsoonal regimes are associated with dynamical interactions between low‐level tropical cyclonic circulations and mid‐level subtropical troughs. Synchronous primary and secondary cyclonic circulations facilitate tropical moisture influx and obstruct the further northward movement of cyclonic circulations, which results in large magnitudes of precipitation at lower elevations in monsoonal regimes. On the other hand, winter regimes exhibit intense western disturbances, which enable orographic ascent of tropical moisture towards higher elevations. Despite weaker dynamical interactions, a stronger thermodynamical instability and a steeper terrain gradient trigger deep convection at higher elevations in transitional regimes. Overall, monsoonal regimes account for 52% of rainy days, whereas winter and transitional regimes account for 20 and 28%, respectively. We present a methodology that identifies hotspots of anomalous precipitation over vulnerable higher elevations by tracking atmospheric variables in Delhi. Our results illustrate the dynamical and thermodynamical interactions responsible for precipitation and highlight the significant contribution from nonmonsoonal regimes to the precipitation across higher elevations in the WH.