A simulation model of morphological,vegetation and sediment changes in ephemeral streams     

J. M. Hooke  C. J. Brookes  W. Duane  J. M. Mant 《地球表面变化过程与地形》2005,30(7):845-866

A model to simulate channel changes in ephemeral river channels and to test the effects of hydrological changes due to climate change and[sol ]or land use change was developed under the auspices of the EU funded MEDALUS programme (Mediterranean Desertification and Land Use). The model, CHANGISM (Channel Change GIS Simulation Model), is designed to simulate the effect of channel flow events and of climate conditions on morphology, sediment and vegetation, through sequences of events and conditions, over periods of up to several decades. The modelling is based on cellular automata but with calculations for water and sediment continuity. Process rules have both deterministic and stochastic elements. An important feature of the model is that it incorporates feedback elements between each event. The main aim of the model is to indicate the likely outcomes of events and combinations of conditions. It is linked to GIS for both input and output. The modelling is based on a channel reach and state is input as GIS layers of morphology (DEM), sediment and vegetation cover and state. Other initial conditions of soil moisture, groundwater level, and overall gradient are input. Parameters for processes are read from tables and can be easily changed for successive runs of the model. The bases for decisions on process specifications are discussed in this paper. Initial tests of the operation and sensitivity of the model were made on idealized reaches. The model was then tested using data from monitored sites in SE Spain. Simulations using clearwater flow worked well but initial simulations using events with sediment loads showed some tendency for excess deposition. Further tests and modifications are taking place. Overall, the model is one of the most sophisticated that simulates the interaction of flows with sediment and vegetation and the outcomes in terms of erosion, deposition, morphology, sediment cover, vegetation cover and plant survival over periods of up to 30 years for the scale of a channel reach. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Stratigraphy of Pleistocene glaciations in the St Elias Mountains,southwest Yukon,Canada          下载免费PDF全文

Derek G. Turner  Brent C. Ward  Duane G. Froese  Michel Lamothe  Jeffrey D. Bond  Nancy H. Bigelow 《Boreas: An International Journal of Quaternary Research》2016,45(3):521-536

At least five Middle to Late Pleistocene advances of the northern Cordilleran Ice Sheet are preserved at Silver Creek, on the northeastern edge of the St Elias Mountains in southwest Yukon, Canada. Silver Creek is located 100 km up‐ice of the Marine Isotope Stage (MIS) 2 McConnell glacial limit of the St Elias lobe. This site contains ~3 km of nearly continuous lateral exposure of glacial and non‐glacial sediments, including multiple tills separated by thick gravel, loess and tilted lake beds. Infrared‐stimulated luminescence (IRSL) and AMS radiocarbon dating constrain the glacial deposits to MIS 2, 4, either MIS 6 or mid‐MIS 7, and two older Middle Pleistocene advances. This chronology and the tilt of the lake beds suggest Pleistocene uplift rates of up to 1.9 mm a^?1 along the Denali Fault since MIS 7. The non‐glacial sediment consists of sand, gravel, loess and organic beds from MIS 7, MIS 3 and the early Holocene. The MIS 3 deposits date to between 30–36 ¹⁴C ka BP, making Silver Creek one of the few well‐constrained MIS 3‐aged sites in Yukon. This confirms that ice receded close to modern limits in MIS 3. Pollen and macrofossil analyses show that a meadow‐tundra to steppe‐tundra mosaic with abundant herbs and forbs and few shrubs or trees, dominated the environment at this time. The stratigraphy at Silver Creek provides a palaeoclimatic record since at least MIS 8 and comprises the oldest direct record of Pleistocene glaciation in southwest Yukon.  相似文献   

Mud volcanoes and evaporite seismites in a tidal flat of northern Kuwait—implications for fluid flow in sabkhas of the Persian (Arabian) Gulf     

Michael J. Duane  Linda Reinink-Smith  Christopher Eastoe  Ali T. Al-Mishwat 《Geo-Marine Letters》2015,35(3):237-246

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Reconstruction of Holocene paleohydrological and sedimentological characteristics of Umm Ar-Rimam basin (northern Kuwait)     

Adeeba?Al-HurbanEmail author  Michael?J.?Duane 《Arabian Journal of Geosciences》2016,9(13):621

The paleohydrological and sedimentological characteristics of a playa lake in northern Kuwait (Arabian Gulf) are reconstructed using sedimentological, geochemical, and isotopic techniques. The sequence consists of up to 8 cycles of S-poor, alluvial sediments capped by a thin organic soil interbedded with gravity-fall calcrete sediments. The succession is locally derived from mainly Quaternary sediments and is regressive with upsection filling of the subsiding basin by cycles of sheetwash flow in response to climatic change. There is no natural, open-water lake water as indicated by low total organic carbon (TOC) data, but the presence of incised calcrete yardangs suggests that more extensive open-water conditions were operative in the past. Stable isotope (δ¹⁸O‰ and δ¹³C‰) values of the authigenic carbonates indicate the following three distinct processes: evaporation, meteoric fluid infiltration, and rapid per-descensum flow (rapid downward movement of water and playa sediment through pipes) through a porous, clastic sequence. Because evaporites are scarce, other factors besides evaporation action control chemical and isotopic compositions of the per-decensum lake fluids. Consequently, the isotopic composition cannot be interpreted exclusively as an indicator of salinity or evaporation ratio. The degassing of CO₂ during groundwater discharge may explain the enriched carbon isotope values for the authigenic carbonates precipitated in the sediments. Hydrologically closed lake water bodies tend to show low negative carbonate oxygen and carbon isotopic signatures. Isotopically negative δ¹³C values imply a strong input of soil-zone carbon to the groundwater of the top 60 cm of the sediment. Lakes that are hydrologically closed and evaporate or equilibrate with atmospheric CO₂ will tend to have low negative δ¹⁸O and δ¹³C values in the carbonates as reported by Talbot (Chem Geol: Isotope Geosci Sect 80(4):261–279, 1990). Biologically active lakes will tend toward lower δ¹³C of dissolved carbon due to the photosynthetic effects of ¹²C withdrawal as reported by Dunagan and Driese (J Sed Res 69:772–783, 1999). Increased biological activity during sedimentation may account for low carbon isotope values where plants were abundant, but in shrinkage-dominated systems (those of clay-rich soil subjecting to wet-dry conditions), carbon isotopes will be largely inherited from the calcretic limestones in the land extending landward of the coast and not influenced by coastal processes (known as hinterland), such as Umm Ar-Rimam depression. This basin does not fit the classic shallow playa-type basins of the Arabian Peninsula but rather the recharge playas of the southwestern USA.  相似文献   

World oil: Hotelling depletion or accelerating use?     

Duane Chapman 《Natural Resources Research》1993,2(4):331-339

In theoretical Hotelling-type models of resource depletion, oil use declines monotonically over time to depletion. However, world oil use has been increasing for several years. Can theory and reality be reconciled? The answer is affirmative, if theory is modified to accommodate outward-shifting demand functions that are rising in response to growth in world population and income. Under this assumption, a Hotelling depletion model projects a 50-year period of increasing world oil use before the decline to exhaustion. This holds for both competitive and monopolistic regimes. Hotelling theory has been criticized by Adelman and others, in part because of the unreality of the theoretical projections. By combining the modified Hotelling theory with U.S. Geological Survey resource estimates, the numerical projections seem congruent with Adelman's near-term expectations. Finally, a backstop technology, such as renewable biomass ethanol, introduces a new dimension. Assuming a $2-per-gallon cost for the ethanol, the modified Hotelling theory projects accelerating use of conventional oil until depletion or substitution. Consequently, it does not seem unreasonable to believe that a finite, limited resource of conventional oil is consistent with growing use for several decades. A projected exhaustion in 100 years is consisten with increasing use for 50 years.  相似文献   

The Use of Specific Capacity to Assess Transmissivity in Fractured-Rock Aquifers   总被引：6，自引：0，他引：6  

David Huntley  Roger Nommensen  Duane Steffey 《Ground water》1992,30(3):396-402

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Representation of tropical subseasonal variability of precipitation in global reanalyses     

Daehyun Kim  Myong-In Lee  Dongmin Kim  Siegfried D. Schubert  Duane E. Waliser  Baijun Tian 《Climate Dynamics》2014,43(1-2):517-534

Tropical subseasonal variability of precipitation from five global reanalyses (RAs) is evaluated against Global Precipitation Climatology Project (GPCP) and Tropical Rainfall Measuring Mission (TRMM) observations. The RAs include the three generations of global RAs from the National Center for Environmental Prediction (NCEP), and two other RAs from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC). The analysis includes comparisons of the seasonal means and subseasonal variances of precipitation, and probability densities of rain intensity in selected areas. In addition, the space–time power spectrum was computed to examine the tropical Madden-Julian Oscillation (MJO) and convectively coupled equatorial waves (CCEWs). The modern RAs show significant improvement in their representation of the mean state and subseasonal variability of precipitation when compared to the two older NCEP RAs: patterns of the seasonal mean state and the amplitude of subseasonal variability are more realistic in the modern RAs. However, the probability density of rain intensity in the modern RAs show discrepancies from observations that are similar to what the old RAs have. The modern RAs show higher coherence of CCEWs with observed variability and more realistic eastward propagation of the MJO precipitation. The modern RAs, however, exhibit common systematic deficiencies including: (1) variability of the CCEWs that tends to be either too weak or too strong, (2) limited coherence with observations for waves other than the MJO, and (3) a systematic phase lead or lag for the higher-frequency waves.  相似文献   

Cloud computing and virtualization within the regional climate model and evaluation system     

Chris A. Mattmann  Duane Waliser  Jinwon Kim  Cameron Goodale  Andrew Hart  Paul Ramirez  Dan Crichton  Paul Zimdars  Maziyar Boustani  Kyo Lee  Paul Loikith  Kim Whitehall  Chris Jack  Bruce Hewitson 《Earth Science Informatics》2014,7(1):1-12

The Regional Climate Model Evaluation System (RCMES) facilitates the rapid, flexible inclusion of NASA observations into climate model evaluations. RCMES provides two fundamental components. A database (RCMED) is a scalable point-oriented cloud database used to elastically store remote sensing observations and to make them available using a space time query interface. The analysis toolkit (RCMET) is a Python-based toolkit that can be delivered as a cloud virtual machine, or as an installer package deployed using Python Buildout to users in order to allow for temporal and spatial regridding, metrics calculation (RMSE, bias, PDFs, etc.) and end-user visualization. RCMET is available to users in an “offline”, lone scientist mode based on a virtual machine dynamically constructed with model outputs and observations to evaluate; or on an institution’s computational cluster seated close to the observations and model outputs. We have leveraged RCMES within the content of the Coordinated Regional Downscaling Experiment (CORDEX) project, working with the University of Cape Town and other institutions to compare the model output to NASA remote sensing data; in addition we are also working with the North American Regional Climate Change Assessment Program (NARCCAP). In this paper we explain the contribution of cloud computing to RCMES’s specifically describing studies of various cloud databases we evaluated for RCMED, and virtualization toolkits for RCMET, and their potential strengths in delivering user-created dynamic regional climate model evaluation virtual machines for our users.  相似文献   

NASA Landsat program accomplishments continue to make a difference II     

Kamlesh Lulla  M. Duane Nellis  Brad Rundquist 《国际地球制图》2013,28(5)

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Commentary on “A Rationale for the National Center for Geographic Information and Analysis”     

M. Duane Nellis 《The Professional geographer》1993,45(2):220-222

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