Complex Topographic Features Research Articles

Reconstruction of Historical Atmospheric Data by a Hydroclimate Model for the Mekong River Basin

It is necessary to have historical atmospheric data at fine time and spatial grid resolutions as input to watershed-scale models of the Mekong River Basin to perform water balance studies over the basin. However, such historical atmospheric data are not available at the desired fine time-space scales for various reasons in this region. Therefore, it is necessary to reconstruct the atmospheric data over the Mekong River Basin at a fine spatial resolution (approximately 20 km) by means of a regional coupled atmospheric-hydrologic model from the available historical global atmospheric data that have a very coarse resolution (approximately 285 km). The coarse resolution (approximately 285 km) reanalysis of atmospheric data for 1956–2006 from the U.S. National Center for Atmospheric Research (NCAR) and the U.S. National Center for Environmental Prediction (NCEP) were used for the reconstruction of the fine resolution (approximately 20 km) historical atmospheric data over the basin. To incorporate the complex topographical and land surface features of this basin, a regional, fully coupled atmospheric-hydrologic hydro-climate model of the Mekong River Basin, called “RegHCM-Mekong,” was developed for the dynamic downscaling. The coarse time-space resolution NCEP-NCAR historical atmospheric data were then downscaled by RegHCM-Mekong to produce meteorological information on rainfall, air temperature, specific humidity, wind velocity, solar radiation, and net radiation at 0.2 degrees spatial resolution (approximately 20 km) and at hourly intervals over the whole Mekong River Basin during a historical period. After a bias correction of the RegHCM-Mekong-downscaled data (by means of Global Precipitation Climatology Project (GPCP) data), the RegHCM-Mekong-reconstructed historical rainfall fields were successfully validated through comparisons against available point-location observations. The comparisons against the interpolated spatial maps of historical precipitation showed satisfactory results.

Flights into the past: full-waveform airborne laser scanning data for archaeological investigation

Airborne Light Detection and Ranging (LiDAR) is a quite recent (mid-1990s) remote sensing technique used to measure terrain elevation. Recent studies have examined the possibility of using LiDAR in archaeological investigations to map and characterize earthworks, to capture features that may be indistinguishable on the ground and to aid the planning of archaeological excavation campaigns. Despite the great potential of LiDAR in archaeology, also linked to its unique capability to penetrate vegetation canopies and identify archaeological earthworks and remains even under dense vegetation cover, the use of airborne laser scanning data encounters serious challenges. Data filtering and processing as well as pattern extraction, classification of terrain information from raw LiDAR data is still a challenging ongoing research. In this paper, we present the data processing chain along with the threshold-based algorithm we devised for the classification of ground and non-ground points and for the detection of archaeological features. The classification of laser data was performed using a strategy based on a set of “filtrations of the filtrate”. Appropriate criteria for the classification and filtering were set to gradually refine the intermediate results in order to obtain the vegetation heights and to discriminate between canopy, understory and micro-topographic relief of archaeological interest. We selected sample areas within two abandoned medieval settlements in Southern Italy characterized by the presence of low and heterogeneous herbaceous cover and complex topographical and morphological features, which make the identification of archaeological features really complex. Results from our investigations pointed out that the applied data processing enables the detection of micro-topographic relief in sparsely as well as in densely vegetated areas. The most important facts to cope with different environmental situations are mainly linked with (i) the resolution of the acquired data set and (ii) the data acquisition and processing chain specifically devised for archaeological purposes.

On the LiDAR contribution for the archaeological and geomorphological study of a deserted medieval village in Southern Italy

Airborne laser scanning (ALS) is an optical measurement technique for obtaining high-precision information about the Earth's surface including basic terrain mapping (digital terrain model, bathymetry, corridor mapping), vegetation cover (forest assessment and inventory) and coastal and urban areas. Recent studies examined the possibility of using ALS in archaeological investigations to identify earthworks, although the ability of ALS measurements in this context has not yet been studied in detail. This paper focuses on the potential of the latest generation of airborne ALS for the detection and the spatial characterization of micro-topographic relief linked to archaeological and geomorphological features. The investigations were carried out near Monteserico, an archaeological area in the Basilicata region (Southern Italy) which is characterized by complex topographical and morphological features. The study emphasizes that the DTM-LiDAR data are a powerful instrument for detecting surface discontinuities relevant for investigating geomorphological processes and cultural features. The LiDAR survey allowed us to identify the urban shape of a medieval village, by capturing the small differences in height produced by surface and shallow archaeological remains (the so-called shadow marks) which were not visible from ground or from optical dataset. In this way, surface reliefs and small elevation changes, linked to geomorphological and archaeological features, have been surveyed with great detail.

Unstructured grid generation using LiDAR data for urban flood inundation modelling

AbstractInundation disasters, caused by sudden water level rise or rapid flow, occur frequently in various parts of the world. Such catastrophes strike not only in thinly populated flood plains or farmland but also in highly populated villages or urban areas. Inundation of the populated areas causes severe damage to the economy, injury, and loss of life; therefore, a proper management scheme for the disaster has to be developed. To predict and manage such adversity, an understanding of the dynamic processes of inundation flow is necessary because risk estimation is performed based on inundation flow information. In this study, we developed a comprehensive method to conduct detailed inundation flow simulations for a populated area with quite complex topographical features using LiDAR (Light Detection and Ranging) data. Detailed geospatial information including the location and shape of each building was extracted from the LiDAR data and used for the grid generation. The developed approach can distinguish buildings from vegetation and treat them differently in the flow model. With this method, a fine unstructured grid can be generated representing the complicated urban land features precisely without exhausting labour for data preparation. The accuracy of the generated grid with different grid spacing and grid type is discussed and the optimal range of grid spacing for direct representation of urban topography is investigated. The developed method is applied to the estimation of inundation flows, which occurred in the basin of the Shin‐minato River. A detailed inundation flow structure is represented by the flow model, and the flow characteristics with respect to topographic features are discussed. Copyright © 2010 John Wiley & Sons, Ltd.

Full-waveform Airborne Laser Scanning for the detection of medieval archaeological microtopographic relief

Abstract This paper focuses on the detection and spatial characterization of microtopographic relief linked to archaeological remains using full-waveform (FW) Airborne Laser Scanning (ALS). ALS is an optical measurement technique for obtaining high-precision information on the Earth's surface including basic terrain mapping, such as Digital Terrain Model (DTM) and Digital Surface Model (DSM). In the field of cultural heritage management, ALS can provide detailed information useful for feature extraction, but the detection of archaeological microtopographic relief is still a challenge especially for vegetated and highly sloped areas. The investigation was carried out for the archaeological area of Monte Irsi (Southern Italy) characterized by dense herbaceous cover and complex topographical and morphological features, which make air/space prospection very difficult. Results from our investigations pointed out that ALS is a valuable data source to detect and map cultural features even under dense vegetation.

Diurnal variation in summer precipitation over the central Tibetan Plateau

The diurnal cycle of rainfall over the central Tibetan Plateau was investigated by examining data acquired by the Tropical Rainfall Measuring Mission Precipitation Radar during the summer monsoon season (June–August) from 1998–2007. High‐spatial‐resolution data (∼5 km × 5 km) were used to identify the role of complex topographic features of the plateau. Diurnal variations in rain rate, frequency of rain, conditional rain rate, and storm‐height were analyzed on a monthly basis to determine the characteristics of precipitation. The results are interpreted as precipitation characteristics in a semiarid region with weak prevailing winds. Distinct diurnal variation was seen over hilly regions, valleys, and lakes. Precipitation activity over the hilly region is generally strongest during the late afternoon. But in contrast, valleys and lakes show dominant late‐evening peaks, and a secondary morning rainfall peak is distinctly evident over large lakes. However, the time of peak rain rate is delayed with increasing lake size. The shift in rain peak location toward lakes and valleys also appeared clearly.

Substrate Topography Induces a Crossover from 2D to 3D Behavior in Fibroblast Migration

In a three-dimensional environment, cells migrate through complex topographical features. Using microstructured substrates, we investigate the role of substrate topography in cell adhesion and migration. To do so, fibroblasts are plated on chemically identical substrates composed of microfabricated pillars. When the dimensions of the pillars (i.e., the diameter, length, and spacing) are varied, migrating cells encounter alternating flat and rough surfaces that depend on the spacing between the pillars. Consequently, we show that substrate topography affects cell shape and migration by modifying cell-to-substrate interactions. Cells on micropillar substrates exhibit more elongated and branched shapes with fewer actin stress fibers compared with cells on flat surfaces. By analyzing the migration paths in various environments, we observe different mechanisms of cell migration, including a persistent type of migration, that depend on the organization of the topographical features. These responses can be attributed to a spatial reorganization of the actin cytoskeleton due to physical constraints and a preferential formation of focal adhesions on the micropillars, with an increased lifetime compared to that observed on flat surfaces. By changing myosin II activity, we show that actomyosin contractility is essential in the cellular response to micron-scale topographic signals. Finally, the analysis of cell movements at the frontier between flat and micropillar substrates shows that cell transmigration through the micropillar substrates depends on the spacing between the pillars.

FILMPAR: A parallel algorithm designed for the efficient and accurate computation of thin film flow on functional surfaces containing micro-structure

FILMPAR is a highly efficient and portable parallel multigrid algorithm for solving a discretised form of the lubrication approximation to three-dimensional, gravity-driven, continuous thin film free-surface flow over substrates containing micro-scale topography. While generally applicable to problems involving heterogeneous and distributed features, for illustrative purposes the algorithm is benchmarked on a distributed memory IBM BlueGene/P computing platform for the case of flow over a single trench topography, enabling direct comparison with complementary experimental data and existing serial multigrid solutions. Parallel performance is assessed as a function of the number of processors employed and shown to lead to super-linear behaviour for the production of mesh-independent solutions. In addition, the approach is used to solve for the case of flow over a complex inter-connected topographical feature and a description provided of how FILMPAR could be adapted relatively simply to solve for a wider class of related thin film flow problems. Program summary Program title: FILMPAR Catalogue identifier: AEEL_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEEL_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 530 421 No. of bytes in distributed program, including test data, etc.: 1 960 313 Distribution format: tar.gz Programming language: C++ and MPI Computer: Desktop, server Operating system: Unix/Linux Mac OS X Has the code been vectorised or parallelised?: Yes. Tested with up to 128 processors RAM: 512 MBytes Classification: 12 External routines: GNU C/C++, MPI Nature of problem: Thin film flows over functional substrates containing well-defined single and complex topographical features are of enormous significance, having a wide variety of engineering, industrial and physical applications. However, despite recent modelling advances, the accurate numerical solution of the equations governing such problems is still at a relatively early stage. Indeed, recent studies employing a simplifying long-wave approximation have shown that highly efficient numerical methods are necessary to solve the resulting lubrication equations in order to achieve the level of grid resolution required to accurately capture the effects of micro- and nano-scale topographical features. Solution method: A portable parallel multigrid algorithm has been developed for the above purpose, for the particular case of flow over submerged topographical features. Within the multigrid framework adopted, a W-cycle is used to accelerate convergence in respect of the time dependent nature of the problem, with relaxation sweeps performed using a fixed number of pre- and post-Red-Black Gauss–Seidel Newton iterations. In addition, the algorithm incorporates automatic adaptive time-stepping to avoid the computational expense associated with repeated time-step failure. Running time: 1.31 minutes using 128 processors on BlueGene/P with a problem size of over 16.7 million mesh points.

Topographic features around Zhongshan Station, southeast of Prydz Bay

Considering the complex topographic features of the southeast of Prydz Bay where China’s Zhongshan Station is located, three types of geomorphologic units can be identified, i.e., submarine slopes, canyons, and terrains. The major topographic features in the study area are the submarine canyon and trough system outside the calving ice front of Dalk Glacier. A 3.8 km × 80 m fissure is found on the submarine terrain at Zhongshan Anchorage, which, once triggered by geological hazards such as earthquakes and ice falls, would be a threat to the usage and maintenance of the anchorage.

Numerical study of the impact of urbanization on the precipitation over Taiwan

A highly developed industry and a large population density have turned the western plain of Taiwan into a mega-suburb with many cities and small towns and countless factories, and roads. As a result, the western plain is experiencing a regional heat-island effect. The MM5 mesoscale model was conducted in order to study and evaluate the impacts of the heat-island effect on regional weather, including thunderstorms, over Taiwan. According to land use data provided by the US Geological Survey (USGS), we assumed three different urban sizes in the simulation study to theoretically evaluate the impact of urbanization on the precipitation. Along with urban size increase in central Taiwan, more pronounced effects of meteorological parameters were shown in the sensitivity experiment with urban cases. For the urban case (case SA, with urban size 15×15 km 2), sensible heat flux is nearly 500 W m −2 around noon-time. It is about a factor of 3 more than the non-urban case (case CT) over the western plain. The surface air temperature in case SA increased by nearly 3 °C and humidity decreased with nearly 10% more than case CT. Along with the urban size increases in central Taiwan, the effects are the surrounding areas and were more pronounced not only the precipitation over downwind areas. Apparently, the unique and complex topographic features in Taiwan, including the lifting effect of the mountain bordering the western plain, are also play important roles for precipitation formation. Numerical study suggests that the heat-island effect over the western plain could perturb thermal and dynamic processes and hence affect the location of thunderstorms and precipitation over Taiwan's western plain.

Investigating the spectral capability of QuickBird data to detect archaeological remains buried under vegetated and not vegetated areas

Abstract The spectral capability of satellite QuickBird imagery for the identification of archaeological marks linked to the presence of buried remains is here discussed for two medieval archaeological sites in the South of Italy. The considered test sites present complex topographical and morphological features, typical of many medieval settlements, which make archaeological prospection with any remote sensing technologies difficult. Results from the performed investigations showed that the satellite QuickBird imagery can be a valuable data source for reconstructing the urban shape of buried settlements up to single building scale. Such analyses can be useful for detecting locations and extracting features of archaeological sites especially prior to any excavation work and for increasing the cultural value of historical sites.

Quantifying the influence of topographic position on cougar (Puma concolor) movement in southern California, USA

AbstractLarge carnivores are frequently used as focal species for landscape‐level planning and conservation purposes. Information on cougars Puma concolor, for example, is being used to predict movement corridors and linkage areas in habitats influenced by rapid urbanization. However, animal movement through habitat terrain is a function of multiple factors, including complex topographic features. To assess the use of topographic position during movements by cougars in the Santa Ana Mountain Range of southern California, we analyzed the travel paths of 10–17 radio‐tagged individuals monitored during 44 overnight sessions. We examined selection for canyon bottom, gentle slope, steep slope and ridgeline topography at the scale of the movement session and at the scale of the home range. At both scales of selection, our results suggest that traveling or hunting cougars discriminated in their use of topographic position, that canyon bottoms and gentle slopes (<6°) ranked highest in compositional analyses of selection, and that these patterns were not highly confounded by the presence of preferred vegetation types. Ridgelines were used significantly less often than other positions. Our novel method of quantifying availability and use of topographic positions permits the assessment of terrain features, such as canyon bottoms, in facilitating cougar movements. For complex landscapes, models of animal movement should consider the topographic context that motivates patterns of habitat use, and should be developed using data obtained and analyzed at the appropriate spatial and temporal scales.

Cellular Responses to Substrate Topography: Role of Myosin II and Focal Adhesion Kinase

Although two-dimensional cultures have been used extensively in cell biological research, most cells in vivo exist in a three-dimensional environment with complex topographical features, which may account for at least part of the striking differences between cells grown in vivo and in vitro. To investigate how substrate topography affects cell shape and movement, we plated fibroblasts on chemically identical polystyrene substrates with either flat surfaces or micron-sized pillars. Compared to cells on flat surfaces, 3T3 cells on pillar substrates showed a more branched shape, an increased linear speed, and a decreased directional stability. These responses may be attributed to stabilization of cell adhesion on pillars coupled to myosin II-dependent contractions toward pillars. Moreover, using FAK−/− fibroblasts we showed that focal adhesion kinase, or FAK, is essential for the responses to substrate topography. We propose that increased surface contact provided by topographic features guides cell migration by regulating the strength of local adhesions and contractions, through a FAK- and myosin II-dependent mechanism.

The influence of palaeotopography on facies architecture and pyroclastic flow processes of a lithic-rich ignimbrite in a high gradient setting: The Abrigo Ignimbrite, Tenerife, Canary Islands

The late Pleistocene (188 ± 19 ka) Abrigo Ignimbrite represents the last major explosive caldera-forming eruption on Tenerife. It consists almost entirely of a moderate volume (≫ 1.8 km 3) light grey phonolitic lithic-rich ignimbrite deposit, although a possible Abrigo Member thin fall deposit is locally preserved beneath the ignimbrite, suggesting an initial short-lived stable plinian eruption column. The ignimbrite deposit is dispersed radially around the lower flanks of the Las Cañadas edifice and correlates to a clast-supported lithic breccia on the eastern and northern caldera wall. Much of the ignimbrite was probably deposited offshore or within the caldera, now buried by more recent lavas. Two major depositional units, separated by a co-ignimbrite ash cloud deposit, and which display dramatic variations in thickness (< 1 to 25 m thick) and facies architecture across the radial drainage pattern, occur across most of the southern coastal plain of the island. Valley-ponded, massive, lithic-rich ignimbrite deposits were deposited by progressive aggradation from a sustained pyroclastic flow. Matrix-supported lithic block concentration zones within depositional units consist of either entrained, locally derived or vent-derived lithic clasts and were deposited in valleys during intervals of relatively high flow energy. Stratified ignimbrite veneer deposits on palaeoridges were deposited by incremental aggradation under pulsatory flow conditions. Valley-ponded to veneer deposit transitions, which occur over even subtle variations in topographic relief, were controlled by the bulk flow velocity, lithic-rich nature (high bulk density) and moderate volume of the pyroclastic flow system. Pumice-rich ignimbrite facies (matrix-supported pumice concentration zones; massive, pumice-rich ignimbrite lobes; planar and laterally complex stratified pumice-rich ignimbrite) were distributed at the deposit front or where the upper pumiceous part of the pyroclastic flow interacted with palaeoridges. Localised facies and bedforms were associated with complex topographic features. Multiple depositional units of massive, lithic-rich ignimbrite occur on the northern and western flanks of the Las Cañadas edifice. The steeper, more vegetated northern flanks also enhanced fines-depletion in the formation of clast-supported lithic breccia. Pyroclastic flows were channelised along and deposited within the same valleys that exist today and were commonly continuous and sheet-like across the interfluves. The basal zones of pyroclastic flows are envisaged as a bed-load of coarse lithic lapilli and blocks transported under their own momentum and with the support of the surrounding fine ash-gas granular flow.

QuickBird‐based analysis for the spatial characterization of archaeological sites: Case study of the Monte Serico medieval village

The potential of high‐resolution QuickBird satellite imagery for archaeological investigations is assessed in the well documented site of Monteserico Village in the Southern Italy. The considered test site presents complex topographical and morphological features, typical of many medieval settlements, which make archaeological prospection with any remote sensing technologies difficult. Results from our investigations showed that the QuickBird fused products can be a valuable data source for reconstructing the urban shape of buried settlements up to single building scale.

A High-Resolution Numerical Simulation of the Wind Flow in the Ross Island Region, Antarctica

Abstract A detailed description of the characteristics of the three-dimensional wind flow for the Ross Island region of Antarctica is presented. This region of Antarctica has complex topographic features, and the wind flow is dependent on the topography and the local meteorological conditions. High-resolution nonhydrostatic numerical simulations are conducted over a high-resolution domain in the Ross Island region. Two simulations are performed corresponding to the two dominant wind flow patterns in the Ross Island region. The first simulation is a light wind case with a stable lower atmosphere and the second is a high wind speed event. Froude number calculations, along with a study of the equation of motion, are included for a more complete understanding of the dynamics of the wind flow. The results of the simulations show a favorable correlation to past research results and observations, and provide a more complete understanding of the three-dimensional wind flow in the region. In addition to a more tho...

Microfabrication of an analog of the basal lamina: biocompatible membranes with complex topographies.

A microfabrication approach was used to produce novel analogs of the basal lamina with complex topographic features. A test pattern of ridges and channels with length scales (40 to 310 micrometer) similar to the invaginations found in a native basal lamina was laser machined into the surface of a polyimide master chip. Negative replicates of the chip were produced using polydimethylsiloxane silicone elastomer and these replicates were used as templates for the production of thin ( approximately 21 micrometer) membranes of collagen or gelatin. The resulting membranes had a complex topography of ridges and channels that recapitulated the features of the master chip. To demonstrate their utility, these complex membranes were laminated to type I collagen sponges and their surfaces were seeded with cultured human epidermal keratinocytes to form a skin equivalent. The keratinocytes formed a differentiated and stratified epidermis that conformed to the features of the microfabricated membrane. The topography of the membrane influenced the differentiation of the keratinocytes because stratification was enhanced in the deeper channels. Membrane topography also controlled the gross surface features of the skin equivalent; infolds of the epidermis increased as channel depth increased. These novel microfabricated analogs of the basal lamina will help to elucidate the influence of topography on epithelial cell proliferation and differentiation and should have applications in the tissue engineering of skin equivalents as well as other basal lamina-containing tissues.

AN ALGEBRAIC GRID GENERATION TECHNIQUE FOR THREE-DIMENSIONAL NATURAL RIVER REACHES

An algebraic grid generation scheme is presented to generate a three-dimensional non-orthogonal boundary-fitted grid for natural river reaches. The smooth distribution of the grid points along any co-ordinate direction, is performed using arc length as the controlling parameter along a cubic spline. The grid concentration in areas of large gradients is done using a simple segmentation process. If required, boundary orthogonality may be achieved through a projection from the boundary to the interior of the physical domain. The final grid is obtained using an iterative procedure in each of the co-ordinate directions. The method is computationally efficient and has been kept very simple. Application of the method is demonstrated by generating a non-orthogonal three-dimensional grid for a 3 mile reach of the Columbia River, downstream of Wanapum Dam. The reach contains a variety of complex topographic features (including two islands) and provides an excellent test case. © 1997 John Wiley & Sons, Ltd.

MODELLING FLOOD HYDRAULICS AND OVERBANK DEPOSITION ON RIVER FLOODPLAINS

This paper outlines a numerical model for the prediction of floodplain inundation sequences, overbank deposition rates and deposit grain size distributions. The model has two main components: first, a simplified hydraulic scheme which predicts floodwater flow depths and velocities, and second, a sediment transport element which employs a mass balance relation describing suspended sediment dispersion by convective and diffusive processes and sediment deposition as a function of particle settling rates. These relationships are solved numerically on a finite difference grid that accurately replicates the complex topographic features typical of natural river floodplains. The model is applied to a 600 m reach of the River Culm, Devon, U.K. using data derived from a range of field and laboratory techniques. Continuous records of river stage and suspended sediment concentration provide the model's upstream boundary input requirements. These are supplemented by measurements of the in situ settling characteristics of the suspended sediment load. The model's sediment transport component is calibrated with the aid of a dataset of measured overbank deposition amounts derived from flood events over a 16 month period. The model is shown to predict complicated floodwater inundation sequences and patterns of suspended sediment dispersion and deposition, which are largely a product of the complex topography of the floodplain. These results compare favourably with observations of overbank processes and are an improvement over those of previous models which have employed relatively simple representations of floodplain geometry. © 1997 by John Wiley & Sons, Ltd.

A Investigation of the Sensitivity of Simulated Precipitation to Model Resolution and Its Implications for Climate Studies

Abstract This paper examines the sensitivity of a regional atmospheric model to horizontal resolution and topographic forcing. The model is run for January and July month-long simulations over the European region at gridpoint spacings ranging from 200 to 50 km and with various topography configurations. Different precipitation parameterizations of complexity and structure similar to those used in present-day climate models are tested. When averaged over the whole continent, the precipitation amounts are more sensitive to gridpoint spacing than to topographic forcing. Topography mostly contributes to spatially redistributing precipitation, and its effect is dominant only over subregions characterized by complex topographical features (e.g., the Alps). Other variables, such as cloudiness, surface energy fluxes, and precipitation intensity distributions are also sensitive to resolution. Finally, simulated precipitation amounts vary with the parameterization scheme used at all resolutions. These results have ...