A priori testing of sparse adaptive polynomial chaos expansions using an ocean general circulation model database   总被引：1，自引：0，他引：1  

Justin Winokur  Patrick Conrad  Ihab Sraj  Omar Knio  Ashwanth Srinivasan  W. Carlisle Thacker  Youssef Marzouk  Mohamed Iskandarani 《Computational Geosciences》2013,17(6):899-911

This work explores the implementation of an adaptive strategy to design sparse ensembles of oceanic simulations suitable for constructing polynomial chaos surrogates. We use a recently developed pseudo-spectral algorithm that is based on a direct application of the Smolyak sparse grid formula and that allows the use of arbitrary admissible sparse grids. The adaptive algorithm is tested using an existing simulation database of the oceanic response to Hurricane Ivan in the Gulf of Mexico. The a priori tests demonstrate that sparse and adaptive pseudo-spectral constructions lead to substantial savings over isotropic sparse sampling in the present setting.  相似文献   

Earth observations during space shuttle mission sts‐69 Endeavour's Images of Earth (September 7–18, 1995)     

Susan Runco  Kamlesh Lulla  David L. Amsbury  Cynthia Evans  M. Justin Wilkinson  Kim Willis 《国际地球制图》2013,28(1):91-104

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Crime on the edges: patterns of crime and land use change   总被引：1，自引：0，他引：1  

Justin Song  Patricia L. Brantingham  Valerie Spicer 《制图学和地理信息科学》2013,40(1):51-61

ABSTRACT

Criminologists have long-known that different locations have varying levels of risk for criminal victimization. Based on the geometry of crime and its corresponding crime generators and crime attractors, edges (boundaries between relatively homogeneous neighborhoods) are locations with an elevated risk of criminal victimization. In this article, we investigate the importance of edges. We find that criminal victimization rates are 2–3 times on an edge compared to elsewhere. However, this effect decreases very quickly moving away from these locations, with the effect gone at 40 meters. This general effect is identified in a number of contexts and locations.  相似文献   

SYNERGICITY: Reinventing the Postindustrial City. Edited by Paul Hardin Kapp and Paul J. Armstrong     

Justin B. Hollander 《Geographical review》2013,103(2):310-312

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Subregionalization of Low-Frequency Summer Drought Variability in the Southeastern United States   总被引：1，自引：0，他引：1  

Jason T. Ortegren  Ashley Weatherall  Justin T. Maxwell 《The Professional geographer》2013,65(2):323-332

Freshwater resources are particularly limited in the Southeastern United States. In recent years, severe summer droughts have placed substantial strain on municipal and industrial water resources, emphasizing the need for further research on the causes of long-term moisture deficits. Previous research has identified a Southeast drought region and specific low-frequency ocean-atmosphere influences on drought. In this article, we identify three distinct subregions of low-frequency summer drought variability in the Southeastern United States using principal components analysis. Multidecadal drought variability is most pronounced in the Southeastern Atlantic Coastal States (SEACS) subregion. The SEACS drought variability is significantly associated with ocean-atmosphere variability in the Atlantic and Pacific basins. The significance of ocean-atmosphere influences on drought in the Southeast is spatially confined within only the SEACS subregion. The Eastern Gulf States (EGS) subregion exhibits a long-term increase in summer moisture that is significantly associated with Northern Hemisphere surface temperature increases during the last century. The peninsular Florida subregion is characterized by high-frequency drought variability that is not associated with any of the climate indexes included in this study.  相似文献   

A method for semi‐automated objective quantification of linear bedforms from multi‐scale digital elevation models     

Pierre W. Cazenave  Justin K. Dix  David O. Lambkin  Lisa C. McNeill 《地球表面变化过程与地形》2013,38(3):221-236

The increasing availability of large, detailed digital representations of the Earth's surface demands the application of objective and quantitative analyses. Given recent advances in the understanding of the mechanisms of formation of linear bedform features from a range of environments, objective measurement of their wavelength, orientation, crest and trough positions, height and asymmetry is highly desirable. These parameters are also of use when determining observation‐based parameters for use in many applications such as numerical modelling, surface classification and sediment transport pathway analysis. Here, we (i) adapt and extend extant techniques to provide a suite of semi‐automatic tools which calculate crest orientation, wavelength, height, asymmetry direction and asymmetry ratios of bedforms, and then (ii) undertake sensitivity tests on synthetic data, increasingly complex seabeds and a very large‐scale (39 000 km²) aeolian dune system. The automated results are compared with traditional, manually derived, measurements at each stage. This new approach successfully analyses different types of topographic data (from aeolian and marine environments) from a range of sources, with tens of millions of data points being processed in a semi‐automated and objective manner within minutes rather than hours or days. The results from these analyses show there is significant variability in all measurable parameters in what might otherwise be considered uniform bedform fields. For example, the dunes of the Rub' al Khali on the Arabian peninsula are shown to exhibit deviations in dimensions from global trends. Morphological and dune asymmetry analysis of the Rub' al Khali suggests parts of the sand sea may be adjusting to a changed wind regime from that during their formation 100 to 10 ka BP. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

The Multiscale TROPIcal CatchmentS critical zone observatory M-TROPICS dataset I: The Nyong River Basin,Cameroon     

Stéphane Audry  Henriette Ateba Bessa  Jean-Pierre Bedimo Bedimo  Jean-Loup Boeglin  Laurie Boithias  Jean-Jacques Braun  Bernard Dupré  Mikael Faucheux  Christelle Lagane  Jean-Christophe Maréchal  Jules Remy Ndam-Ngoupayou  Bernadette Nka Nnomo  Justin Nlozoa  Jean-Claude Ntonga  Olivier Ribolzi  Jean Riotte  Emma Rochelle-Newall  Laurent Ruiz 《水文研究》2021,35(5):e14138

Simultaneously acquiring time series of climate, hydrology and hydrochemical data over decades on river systems is pivotal to understand the complex interactions involving rock, soil water, air and biota in the Critical Zone, to build integrated modelling and to propose predictive scenarios. Among the Critical Zone Observatories (CZOs) implemented in the past 25 years, only a few are located in the humid Tropics despite the importance of these regions in terms of population density, fast-changing land use, biodiversity hotspots, biomass stock on continents, size of river systems, etc. Since 1994, weathering and erosion processes and fluxes have been investigated at both local (experimental watershed) and regional scales in the Nyong River Basin (Cameroon) which belongs to the Critical Zone Observatories network named Multiscale TROPIcal CatchmentS (M-TROPICS). The data shared by M-TROPICS in Cameroon are: (1) rainfall; (2) air temperature, air relative humidity, wind speed and direction, and global radiation; (3) stream and river water level; (4) pH, electrical conductivity, water temperature and suspended particulate matter (SPM) concentration; (5) major ion, alkalinity and dissolved organic carbon (DOC) concentrations. The dataset already contributed to describe the water partitioning in these tropical humid watersheds, to better understand the factors controlling chemical weathering and physical erosion in tropical ecosystems, particularly the role of organic matter. The dataset also contributed to calculate elemental weathering fluxes and saprolite production rate and to propose denudation rates on tropical cratonic landscapes. Hydrological modelling allowed quantification of the geographical water sources contributing to streamflow. DOC data were used to determine greenhouse-gas emissions and carbon budgets from African inland waters. However, long-term solute concentrations at the outlet of a small tributary of the Nyong River exhibit non-stationary behaviour over the last 26 years. The processes governing those fluctuations are not yet fully understood and might be related to changes in the hydrological regime, land-cover and land-use. The latter highlights the need for longer time-series and continued support for CZOs particularly in the humid tropics.  相似文献   

High‐pressure metamorphic mineralogy of the Martian crust with implications for density and seismic profiles     

Julia Semprich  Justin Filiberto 《Meteoritics & planetary science》2020,55(7):1600-1614

Here, we calculate the mineralogy of the Martian lower crust and upper mantle as a function of pressure and temperature with depth using four bulk compositions (average crust, Gusev basalt, olivine‐phyric shergottite, and primitive average mantle). We then use this mineralogy to extract rock properties such as density and seismic velocities, describe their changes with varying conditions and geotherms, and make predictions for the crust–mantle boundary. Mineralogically, all compositions produce garnet, orthopyroxene, clinopyroxene in varying proportions at high pressures, with differences in minor minerals (spinel, ilmenite, rutile, and/or K‐feldspar). According to our calculations, the average crust and Gusev basalt compositions have the potential to yield higher densities than the average mantle composition, particularly for thicker crusts and/or colder geotherms. Therefore, recycling of the Martian crust into the mantle could occur through the process of crustal delamination, if not kinetically inhibited. However, our results show that, depending on crustal thickness, the crust may not be easily distinguishable from the mantle in seismic properties.  相似文献   

Anthropocene dwelling: Lessons from post-disaster Christchurch     

Justin Westgate 《New Zealand geographer》2020,76(1):26-38

This article takes circumstances of post-quake Christchurch as an analogue for Anthropocene emergency. I argue that Christchurch events are more than a reminder of the Earth's geologic volatility; for the Anthropocene-as-disaster, it is a prompt to contemplate what it is to dwell on unstable ground. Urban locations—towns, cities, mega-cities—are all rendered vulnerable on the surface of an unruly planet, offering no absolute refuge from planetary fluctuations. Such unsettling is deeply felt, physically and psychologically, resulting in homelessness both literal and figurative. Ensuing analysis offers insight into potential strategies for unsettled planetary dwelling to come.  相似文献   

U‐Pb zircon dating of metaigneous rocks from the Nordbreen Nappe of Svalbard’s Ny‐Friesland suggests their affinity to Northeast Greenland     

Jakub Bazarnik  Jaros&#x;aw Majka  William C. McClelland  Justin V. Strauss  Karolina Komi&#x;ska  Karsten Piepjohn  Synnve Elvevold  Zbigniew Czupyt  Tom&#x; Miku&#x; 《地学学报》2019,31(6):518-526

SIMS U‐Pb zircon dating of metaigneous rocks of the Nordbreen Nappe from the West Ny‐Friesland terrane (Eastern Basement Province of Svalbard) yields crystallization ages of 1,761 ± 4 Ma for a felsic metatuff and 1,373 ± 4 Ma for a metagabbro dyke. The Palaeoproterozoic age of the metatuff is similar to previously obtained ages for various felsic rocks from the study area, whereas the Mesoproterozoic age of the metagabbro has not been thus far documented on Svalbard. However, a similar age pattern has been reported from Northeast Greenland. Therefore, we conclude that the West Ny‐Friesland terrane can be correlated with age equivalent units of Northeast Greenland. We also explore similarities and dissimilarities between the study area and other terranes of Svalbard and speculate on regional‐scale correlations. Together, the presented new ages provide critical piercing points in palaeogeographic reconstructions of the relatively poorly understood circum‐Arctic region.  相似文献