Gaussian plume modeling of contaminant transport     

Chris Kennedy  Hans Ericsson  P. L. R. Wong 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(1-2):119-125

A technique for modeling contaminant transport based on Markov process theory is developed. Transport is quantified by summing the first two moments of independent random displacements and applying the central limit theorem (CLT) to obtain solute distributions of a Gaussian nature. For non-uniform flow fields the CLT is applied in a streamfunction/equi-travel time space and transforms are used to give concentrations in Cartesian coordinates. Simulations in uniform, radially converging and circular flow fields show the method to be two to three orders of magnitude faster than modeling with the advection-dispersion equation, using a control volume technique.  相似文献   

Cosmogenic ¹⁰BE Age Constraints for The Wester Ross Readvance Moraine: Insights Into British Ice-Sheet Behaviour     

Jeremy D. Everest  Tom Bradwell  Chris J. Fogwill  Peter W. Kubik 《Geografiska Annaler: Series A, Physical Geography》2006,88(1):9-17

This study presents the first absoluteage constraints from a palaeo‐ice‐sheet margin in western Scotland. Cosmogenic ¹⁰Be from four Lewisian gneiss boulders on the Gairloch Moraine in NW Scotland have yielded reliable exposure ages. Three of these dates, taken from a single moraine ridge, cluster around c. 15.5–18 ka BP, with a weighted mean of 16.3 ± 1.6 ka BP. These findings indicate that the last British Ice Sheet had retreated to the present‐day coastline in NW Scotland by this time. It is suggested that the Wester Ross Readvance represents an ice‐sheet oscillation during, or in the immediate aftermath of, Heinrich Event 1 (c. 17–18 ka BP).  相似文献   

A transboundary study of urban sprawl in the Pacific Coast region of North America: The benefits of multiple measurement methods     

Chris Davis  Tim Schaub   《International Journal of Applied Earth Observation and Geoinformation》2005,7(4):268-283

Sprawling urban development has emerged as a primary concern of policy makers, land preservationists and both urban and rural communities in developing regions across the globe. For the first time in history, more global residents lived in urban areas than not and the trend to urbanization is in full force at the start of the 21st century. An understanding of the nature and character of urban sprawl is complicated by a failure to satisfactorily define it and by the limitations of measurement techniques designed to characterize complex landscape forms. Like other landscape patterns, the quantification of urban sprawl is highly spatially and temporally scale-dependent. This paper summarizes a recent project to measure urban sprawl in the transboundary region of the Pacific Coast of North America. The metropolitan centers of Portland, OR, Seattle, WA and Vancouver, BC, span two nations, three state/provincial governments and dozens of cities. As a region, this was a global leader in population growth in the 1990s. The study relied on three separate methods – an impervious surface metric, a neighborhood density metric and a building permit metric – for quantifying urban growth. The results provide insight on the strengths and shortcomings of different methods with respect to the challenges posed by data availability and format. Taken together they demonstrate the richer understanding that combined methods may offer in characterizing phenomena as difficult to communicate and agree upon as urban sprawl.  相似文献   

Acidification in European mountain lake districts: A regional assessment of critical load exceedance   总被引：1，自引：0，他引：1  

Chris J. Curtis  Ivan Botev  Lluis Camarero  Jordi Catalan  Dan Cogalniceanu  Mike Hughes  Martin Kernan  Jiří Kopáček  Atte Korhola  Roland Psenner  Michela Rogora  Evžen Stuchlík  Mauro Veronesi  Richard F. Wright 《Aquatic Sciences - Research Across Boundaries》2005,67(3):237-251

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Adaptive traveltime tomography of densely sampled seismic data   总被引：1，自引：0，他引：1  

Immo Trinks  Satish C. Singh  Chris H. Chapman  Penny J. Barton  Miguel Bosch  Adam Cherrett 《Geophysical Journal International》2005,160(3):925-938

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Profile response of a lacustrine multiple barred nearshore to a sequence of storm events     

Chris Houser  Brian Greenwood 《Geomorphology》2005,69(1-4):118-137

Profile change in a lacustrine multiple-barred nearshore was investigated over the ice-free season of 2001/2002 at Burley Beach on the southeastern shore of Lake Huron in order to identify the feedback mechanisms between the pre-existing morphology and the wave forcing and the consequence of those feedbacks to the behaviour of the nearshore environment. The characteristics of the offshore wave field were monitored using a Falmouth Scientific combined 3D-ACM wave recorder and pressure transducer. Supplemental wave data were downloaded from a 3-m discus buoy operated by the National Data Buoy Center, 75 km to the NW of the study site. The three nearshore bars were in a quasi-equilibrium state through a large part of the ice-free season, with dramatic changes occurring during relatively moderate storm events that followed much larger storms in late October. A comparison of the incident wave field with changes in the nearshore profile through canonical correlation analysis indicates that the morphology responds to the distribution of the significant, root-mean-square (rms) and average wave heights between surveys. The threshold between bar decay and onshore bar migration and growth is associated with the onset of breaking of the rms wave at the bar crest (H_rms h_cr⁻¹ ≈0.3–0.4). The threshold between onshore and offshore migration is associated with the onset of breaking of the average wave at the bar crest (H_avg h_cr⁻¹ ≈0.3–0.4), coincident with complete dissipation of the significant wave over the lakeward slope of the bar (H_s h_cr⁻¹ >0.6). Inshore wave data collected during an instrumented study at the same site revealed that the middle and inner bars remained at the threshold of onshore and offshore migration over a wide range of offshore significant wave heights (0.8 to 2.4 m) prior to the October storms. This self-organised equilibrium is a result of changes to the incident wave distribution through breaking on the outer bar. It is concluded that the prediction of bar response requires an understanding of the feedback between the bar and the local wave distribution in addition to an understanding of the feedback associated with the profile as a whole.  相似文献   

Inference of past climate from borehole temperature data using Bayesian Reversible Jump Markov chain Monte Carlo     

Peter O. Hopcroft  Kerry Gallagher  Chris C. Pain 《Geophysical Journal International》2007,171(3):1430-1439

Estimates of past climate derived from borehole temperatures are assuming a greater importance in context of the millennial temperature variation debate. However, recovery of these signals is usually performed with regularization which can potentially lead to underestimation of past variation when noise is present. In this work Bayesian inference is applied to this problem with no explicit regularization. To achieve this Reversible Jump Markov chain Monte Carlo is employed, and this allows models of varying complexity (i.e. variable dimensions) to be sampled so that it is possible to infer the level of ground surface temperature (GST) history resolution appropriate to the data. Using synthetic examples, we show that the inference of the GST signal back to more than 500 yr is robust given boreholes of 500 m depth and moderate noise levels and discuss the associated uncertainties. We compare the prior information we have used with the inferred posterior distribution to show which parts of the GST reconstructions are independent of this prior information. We demonstrate the application of the method to real data using five boreholes from southern England. These are modelled both individually and jointly, and appear to indicate a spatial trend of warming over 500 yr across the south of the country.  相似文献   

Lagoon subsidence and tsunami on the West Coast of New Zealand     

S.L. Nichol  J.R. Goff  R.J.N. Devoy  C. Chagu-Goff  B. Hayward  I. James 《Sedimentary Geology》2007,200(3-4):248-262

Sediment core and trench data from a coastal lagoon on the West Coast of the South Island, New Zealand are used to investigate evidence for co-seismic subsidence and associated tsunami inundation. Physical data are used to document a salt marsh soil buried  80 cm below the modern sediment surface that is locally covered by a gravelly sand bed. The sediment record also contains geochemical and biological (diatom and foram) evidence for abrupt changes in salinity of lagoon waters that link to subsidence, tsunami flooding and to the open versus closed state of the lagoon tidal entrance. At the local scale, these relationships allow for separation of tsunami evidence from other agents of environmental change in the lagoon. We also propose a conceptual connection between these local changes and regional drivers of landscape development, most notably major earthquakes and resultant pulses in sediment supply to the coast.  相似文献   

Realizing the Literate Traveller     

William E Cartwright  Bob Williams  Chris Pettit 《Transactions in GIS》2007,11(1):9-27

A current research project is addressing the problem of finding appropriate geographical information by developing a (geo)information realization resource based upon the concepts of the Literate Traveller. It has as its main goal to provide tools for geographical knowledge building and exploration, by providing conventional spatial information plus geographical interpretation and appreciation artifacts. These artifacts are delivered in an interactive multimedia environment. This research examines the formulation of an initial prototype component to assist in providing geographical knowledge. The prototype is based on a study site in Townsville, Australia, and is being used as a vehicle to explore enhanced spatial information provision through the use of rich media. The research examines new ways to prospect for, discover and disseminate spatial knowledge within an intelligence‐briefing context. The paper reports on the concepts behind the design of the application developed for the test site, and presents initial findings from the early evaluation of the prototype.  相似文献   

On 50th Anniversary of the Global Carbon Dioxide Record     

Georgii A Alexandrov  Martin Heimann  Chris D Jones  Pieter Tans 《Carbon balance and management》2007,2(1):11-2

The 50-year global CO₂ record led the way in establishing a scientific fact: modern civilization is changing important properties of the global atmosphere, oceans and biosphere. The evidence on which this scientific fact is based will be refined further, but the next challenge for scientists is broader. In addition to its traditional role in providing discovery, diagnosis, and prediction of the changes that are taking place on our planet, science has now also a role in helping society mitigate emissions by objectively quantifying them, and in helping adaptation by providing environmental forecasts on regional scales. Science is also expected to provide new options for society to tackle the transition to a new energy system, and to provide thorough environmental evaluation of all such options. This is what the meeting recognized as planetary responsibilities for scientists in the next 50 years.  相似文献