Cartographic support for locational problem‐solving by groups     

M. P. Armstrong  P. J. Densham 《International journal of geographical information science》2013,27(7):721-749

Collaborative spatial decision‐making environments in which group members individually and collectively pursue solutions to semi‐structured problems have a unique set of geographic visualization requirements. Group members often pursue diverse strategies as they attempt to solve such problems. As a consequence, numerous mapped representations of alternative solutions are generated. It is difficult to compare and synthesize these results, especially when decision‐makers have little or no previous cartographic training. In this paper, we derive several map types that synthesize representations of alternative solutions to location‐selection problems. These synthetic maps, designed to be accessible to group members, are created by decomposing solutions into a collection of atomic elements that are then placed into an accounting framework. Network map algebra operations are performed within this framework, and the results are accumulated and displayed as maps. Group members can use these maps to identify similar and dissimilar elements of alternative solutions to a problem. Such maps are intended to promote discussion and support group consensus‐building activities.  相似文献   

Hydroclimatic flood trends in the northeastern United States and linkages with large-scale atmospheric circulation patterns     

William H. Armstrong  Mathias J. Collins  Noah P. Snyder 《水文科学杂志》2013,58(9):1636-1655

Abstract

We evaluate flood magnitude and frequency trends across the Mid-Atlantic USA at stream gauges selected for long record lengths and climate sensitivity, and find field significant increases. Fifty-three of 75 study gauges show upward trends in annual flood magnitude, with 12 showing increases at p < 0.05. We investigate trends in flood frequency using partial duration series data and document upward trends at 75% of gauges, with 27% increasing at p < 0.05. Many study gauges show evidence for step increases in flood magnitude and/or frequency around 1970. Expanding our study area to include New England, we find evidence for lagged positive relationships between the winter North Atlantic Oscillation phase and flood magnitude and frequency. Our results suggest hydroclimatic changes in regional flood response that are related to a combination of factors, including cyclic atmospheric variability and secular trends related to climate warming affecting both antecedent conditions and event-scale processes.

Editor Z.W. Kundzewicz; Associate editor H. Lins  相似文献   

The changing environment of fisheries policy in Europe     

Margrethe Aanesen  Claire W. Armstrong  Luc van Hoof 《Marine Policy》2012

This paper presents how environmental concerns emanating outside the Common Fisheries Policy (CFP) are increasingly setting the stage for EU fisheries management. This is illustrated via what is termed the exogenous entrance of environmental concerns through the implementation of directives in EU policy. More endogenous entrance of environmental concerns occurs via stakeholder participation in Regional Advisory Councils (RACs) as well as market mechanisms, such as ecolabelling and traceability. This study discusses how these latter channels of environmental concern may have become a more potent and efficient way of reaching environmental goals, outside of the primacy of the CFP.  相似文献   

U–Pb SHRIMP ages and tectonic setting of the Munster Suite of the Margate Terrane of the Natal Metamorphic Belt     

P. Mendonidis  R.A. Armstrong  G.H. Grantham 《Gondwana Research》2009,15(1):28-37

New U–Pb Zircon SHRIMP ages of 1091 ± 7.1 Ma and 1093.1 ± 5.8 Ma have been determined for two discrete phases of the Munster Suite. The Munster Suite is a calc-alkaline mafic to intermediate suite of intrusive igneous rocks that form part of the southern-most tectonic Terrane of the Mesoproterozoic-aged Natal Metamorphic Belt. Previously published geochemical data indicate that the discrete phases of the Suite are consanguineous and that these rocks originated within an oceanic island arc environment. The new age determinations now show that the different phases are also coeval. Moreover, the ages also indicate that the intrusions were, within statistical error, coeval with S-type granites within the Terrane. This is interpreted to indicate that magmatic underplating provided both the magma by way of a number of progressively more evolved pulses to produce the Munster Suite, as well as the heat necessary for crustal melting to produce the S-type granites within an island arc environment. Therefore, these new age determinations indicate a period of crustal growth at circa 1090 Ma. This moreover, is a maximum constraint on the age of the northward-verging structures within the Margate Terrane.  相似文献   

Sources and losses of energetic protons in Saturn's magnetosphere     

C. Paranicas  D.G. Mitchell  D.C. Hamilton  N. Krupp  R.E. Johnson  T.P. Armstrong 《Icarus》2008,197(2):519-525

We present Cassini data revealing that protons between a few keV and about 100 keV energy are not stably trapped in Saturn's inner magnetosphere. Instead these ions are present only for relatively short times following injections. Injected protons are lost principally because the neutral gas cloud converts these particles to energetic neutral atoms via charge exchange. At higher energies, in the MeV to GeV range, protons are stably trapped between the orbits of the principal moons because the proton cross-section for charge exchange is very small at such energies. These protons likely result from cosmic ray albedo neutron decay (CRAND) and are lost principally to interactions with satellite surfaces and ring particles during magnetospheric radial diffusion. A main result of this work is to show that the dominant energetic proton loss and source processes are a function of proton energy. Surface sputtering by keV ions is revisited based on the reduced ion intensities observed. Relatively speaking, MeV ion and electron weathering is most important closer to Saturn, e.g. at Janus and Mimas, whereas keV ion weathering is most important farther out, at Dione and Rhea.  相似文献   

Initial yield to depth relation for water wells drilled into crystalline bedrock--Pinardville quadrangle, New Hampshire     

Drew LJ  Schuenemeyer JH  Armstrong TR  Sutphin DM 《Ground water》2001,39(5):676-684

A model is proposed to explain the statistical relations between the mean initial water well yields from eight time increments from 1984 to 1998 for wells drilled into the crystalline bedrock aquifer system in the Pinardville area of southern New Hampshire and the type of bedrock, mean well depth, and mean well elevation. Statistical analyses show that the mean total yield of drilling increments is positively correlated with mean total well depth and mean well elevation. In addition, the mean total well yield varies with rock type from a minimum of 46.9 L/min (12.4 gpm) in the Damon Pond granite to a maximum of 74.5 L/min (19.7 gpm) in the Permian pegmatite and granite unit. Across the eight drilling increments that comprise 211 wells each, the percentages of very low-yield wells (1.9 L/min [0.5 gpm] or less) and high-yield wells (151.4 L/min [40 gpm] or more) increased, and those of intermediate-yield wells decreased. As housing development progressed during the 1984 to 1998 interval, the mean depth of the wells and their elevations increased, and the mix of percentages of the bedrock types drilled changed markedly. The proposed model uses a feed-forward mechanism to explain the interaction between the increasing mean elevation, mean well depth, and percentages of very low-yielding wells and the mean well yield. The increasing percentages of very low-yielding wells through time and the economics of the housing market may control the system that forces the mean well depths, percentages of high-yield wells, and mean well yields to increase. The reason for the increasing percentages of very low-yield wells is uncertain, but the explanation is believed to involve the complex structural geology and tectonic history of the Pinardville quadrangle.  相似文献   

A strontium isotope evolution model for cenozoic magma genesis,Estern Great Basin,U.S.A.     

R. B. Scott  R. W. Nesbitt  E. Julius Dasch  R. L. Armstrong 《Bulletin of Volcanology》1971,35(1):1-26

Cenozoic volcanism in the Great Basin is characterized by an outward migration of volcanic centers with time from a centrally located core region, a gradational decrease in the initial Sr⁸⁷/Sr⁸⁶ ratio with decreasing age and increasing distance from the core, and a progressive change from calc-alkalic core rocks to more alkalic basin margin rocks. Generally each volcanic center erupted copious silicic ignimbrites followed by small amounts of basalt and andesite. The Sr⁸²/Sr⁸⁶ ratio for old core rocks is about 0.709 and the ratio for young basin margin rocks is about 0.705. Spatially and temporally related silicic and mafic suites have essentially the same Sr⁸⁷/Sr⁸⁶ ratios. The locus of older volcanism of the core region was the intersection of a north-south trending axis of crustal extension and high heat flow with the northeast trending relic thermal ridge of the Mesozoic metamorphic hinterland of the Sevier Orogenic Belt. Derivation of the Great Basin magmas directly from mantle with modification by crustal contamination seems unlikely. Initial melting of lower crustal rocks probably occurred as a response to decrease in confining pressure related to crustal extension. Volcanism was probably also a consequence of the regional increase in the geothermal gradient that is now responsible for the high heat flow of the Basin and Range Province. High Sr isotopic ratios of the older core volcanic rocks suggests that conditions suitable for the production of silicic magmas by partial fusion of the crust reached higher levels within the crust during initial volcanism than during production of later magmas with lower isotopic ratios and more alkaline chemistry. As the Great Basin became increasingly attenuated, progressively lower portions of the crust along basin margins were exposed to conditions suitable for magma genesis. The core region became exhausted in low temperature melting components, and volcanism ceased in the core before nearby areas had completed the silicic-mafic eruption cycle leading to their own exhaustion of crustal magma sources.  相似文献   

Disjunctive kriging revisited: Part I     

M. Armstrong  G. Matheron 《Mathematical Geology》1986,18(8):711-728

Difficulties in applying disjunctive kriging (D.K.) with an anamorphosis to a normal distribution have led to an interest in D.K. based on other distributions. After reviewing Gaussian D.K., this paper reviews other types of D.K. based on other infinitely divisible distributions (gamma, Poisson, and negative binomial).  相似文献   

A data-model intercomparison study of Arctic sea-ice variability   总被引：1，自引：0，他引：1  

Armstrong  A.  Tremblay  L.-B.  Mysak  L. 《Climate Dynamics》2003,20(5):465-476

The dynamic-thermodynamic granular rheology sea-ice model of Tremblay and Mysak is validated against 40 years of observed sea-ice concentration (SIC) data. Subsequently, the mechanisms responsible for producing SIC anomalies in the model are evaluated by studying the coupled variance (using the singular value decomposition method, SVD) between the simulated SIC anomalies and the ice speed and air temperature anomalies. To execute this validation, a 49-year (1949-97) simulation (including a 9-year spin-up period) of the Arctic and peripheral sea-ice cover using daily varying winds and monthly mean air temperatures is produced. In general, the simulated SIC variations for 1958-97 in the East Siberian, Chukchi and Beaufort seas are in agreement with observations, while larger discrepancies occur in the Laptev and Kara seas. Moreover, the sensitivity of the model to southerly wind anomalies in creating summer SIC anomalies compares well with the observed sensitivity; however, the model's sensitivity to summer air temperature anomalies is weaker than observed. The summer SIC anomalies over an entire sea are not influenced by variations in the level of river runoff. Results from the SVD analysis show that the main source of variability in the peripheral seas is associated with the variation in the strength of the Arctic High; in the East Siberian and Laptev seas, the strengthening and weakening of the Transpolar Drift Stream also play an important role. Over the entire Arctic domain, surface air temperature anomalies are negatively correlated with sea-ice anomalies. Finally, the observed downward trend in total sea-ice cover in the last two decades as well as record minima in the East Siberian Sea are well reproduced in the simulation.  相似文献   

Provenance ages of the Neoproterozoic Katanga Supergroup (Central African Copperbelt), with implications for basin evolution   总被引：2，自引：0，他引：2  

S. Master  C. Rainaud  R.A. Armstrong  D. Phillips  L.J. Robb 《Journal of African Earth Sciences》2005,42(1-5):41

New age data on detrital zircons and micas are presented from key units within the Neoproterozoic Katanga Supergroup, which hosts the major stratiform Cu–Co deposits of the Central African Copperbelt. Detrital zircon ages indicate a mainly Palaeoproterozoic (between 2081 ± 28 and 1836 ± 26 Ma) provenance for the Katanga basin, derived from the Lufubu Metamorphic Complex of the Kafue Anticline and the Bangweulu Block to the north of the outcrop belt. Detrital zircons and clasts from the Grand Conglomerat glacial diamictite indicate a source from the Palaeoproterozoic metavolcanic porphyries and granitoids of Luina Dome region, which was a basement high during Nguba Group deposition. Minor zircons of Mesoproterozoic age may have been derived from the Kibaran belt. Finally, ⁴⁰Ar/³⁹Ar age data from detrital muscovites from Biano Group siltstones give a maximum age of sedimentation of 573 Ma, strongly supporting previous models that the Biano Group was deposited in a foreland basin of the Lufilian Orogen.  相似文献