A Spatial Data Infrastructure Approach for the Characterization of New Zealand's Groundwater Systems   总被引：1，自引：0，他引：1       下载免费PDF全文

Alexander Kmoch  Hermann Klug  Alistair B. H. Ritchie  Jochen Schmidt  Paul A. White 《Transactions in GIS》2016,20(4):626-641

The future information needs of stakeholders for hydrogeological and hydro‐climate data management and assessment in New Zealand may be met with an Open Geospatial Consortium (OGC) standards‐compliant publicly accessible web services framework which aims to provide integrated use of groundwater information and environmental observation data in general. The stages of the framework development described in this article are search and discovery as well as data collection and access with (meta)data services, which are developed in a community process. The concept and prototype implementation of OGC‐compliant web services for groundwater and hydro‐climate data include demonstration data services that present multiple distributed datasets of environmental observations. The results also iterate over the stakeholder community process and the refined profile of OGC services for environmental observation data sharing within the New Zealand Spatial Data Infrastructure (SDI) landscape, including datasets from the National Groundwater Monitoring Program and the New Zealand Climate Database along with datasets from affiliated regional councils at regional‐ and sub‐regional scales. With the definition of the New Zealand observation data profile we show that current state‐of‐the‐art standards do not necessarily need to be improved, but that the community has to agree upon how to use these standards in an iterative process.  相似文献   

Safeguarding the future of oceanic fisheries under climate change depends on timely preparation     

Jim Salinger  Alistair J. Hobday 《Climatic change》2013,119(1):3-8

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The effects of temperature and moisture on after-ripening of Cenchrus ciliaris seeds     

Farzad Sharif-Zadeh  Alistair J. Murdoch 《Journal of Arid Environments》2001,49(4):823

After-ripening of Cenchrus ciliaris L. spikelets was modelled during storage at various temperatures and equilibrium relative humidities (e.r.h.). At 40 and 50% e.r.h., the rate of after-ripening increased linearly with increase of storage temperature. The highest after-ripening rate was achieved by storing the seeds in 40°C and 50% e.r.h. At 70% e.r.h., however, seeds remained viable at 20 and 30°C but largely failed to after-ripen. Use of the model to predict the storage period required for decreasing dormancy to any desired level is described. The application to re-seeding degraded rangelands in arid areas is discussed.  相似文献   

Turbulent flow structure in a gravel-bed river: Markov chain analysis of the fluctuating velocity profile     

Alistair D. Kirkbride  Rob Ferguson 《地球表面变化过程与地形》1995,20(8):721-733

Three electromagnetic current meter probes were deployed in a Canadian gravel-bed river to obtain simultaneous records at 10 Hz of streamwise (u) and vertical (v) velocity components at three heights above the bed. By looking at the positive and negative signs of the instantaneous fluctuations from the time-average values of each velocity component at each height, the fluctuating velocity profile of u or v can be treated as a Markov chain with eight states and its statistical properties can be tested against null hypotheses based on the absence of spatial structure. We report results of this novel approach. The most common states of the u profile were those with either higher-than-average or lower-than-average velocities at all heights; these ‘high speed’ and ‘low speed’ states persisted for up to 3 s. The most common v profiles were all-upwards or all-downwards, but these persisted for shorter times than the high speed and low speed u profiles. Analysis of transition probabilities shows statistically significant tendencies for acceleration from the low speed u profile, and change from all-upwards to all-downwards v profile, to take place progressively from the uppermost probe downwards, in a sweep-like way. Deceleration from the high speed to low speed u profile and change from all-downwards to all-upwards v profile (burst-like behaviour) do not show such clear patterns. The results are interpreted in terms of the advection of inverted wedges of relatively high-momentum fluid, followed by more chaotic structures. A separate set of flow visualization experiments over a mixed gravel bed in a flume supports the presence of advected wedge structures, the decelerating part of the sequence corresponding to irregular ejections of near-bed fluid.  相似文献   

Uncertainty assessment in river flow projections for Ethiopia’s Upper Awash Basin using multiple GCMs and hydrological models     

Wilson C. H. Chan  Julian R. Thompson  Richard G. Taylor  Alistair E. Nay  Tenalem Ayenew  Alan M. MacDonald 《水文科学杂志》2020,65(10):1720-1737

ABSTRACT

Uncertainty in climate change impacts on river discharge in the Upper Awash Basin, Ethiopia, is assessed using five MIKE SHE hydrological models, six CMIP5 general circulation models (GCMs) and two representative concentration pathways (RCP) scenarios for the period 2071–2100. Hydrological models vary in their spatial distribution and process representations of unsaturated and saturated zones. Very good performance is achieved for 1975–1999 (NSE: 0.65–0.8; r: 0.79–0.93). GCM-related uncertainty dominates variability in projections of high and mean discharges (mean: –34% to +55% for RCP4.5, – 2% to +195% for RCP8.5). Although GCMs dominate uncertainty in projected low flows, inter-hydrological model uncertainty is considerable (RCP4.5: –60% to +228%, RCP8.5: –86% to +337%). Analysis of variance uncertainty attribution reveals that GCM-related uncertainty occupies, on average, 68% of total uncertainty for median and high flows and hydrological models no more than 1%. For low flows, hydrological model uncertainty occupies, on average, 18% of total uncertainty; GCM-related uncertainty remains substantial (average: 28%).  相似文献   

Rapid zonation of abrupt mass movement hazard: Part I. General principles     

J.R. Ni  R.Z. Liu  Onyx W.H. Wai  Alistair G.L. Borthwick  X.D. Ge   《Geomorphology》2006,80(3-4):214-225

Hazards caused by mass movement cost many human lives and cause severe damage to property. Accurate zonation of such hazards provides an important tool for preventive measures. Previous approaches for mass movement hazard zonation are costly because they require large amounts of data, time and labor, and are only applicable to specific local areas. In this paper, a Rapid Zonation of Abrupt Mass-movement Hazard (RZAMH), applicable to large regions, is proposed. It involves the selection of appropriate zonation principles, routes, units, and indexes that can be used for the classification of reference groups, identification of matching groups of test sites, evaluation of blank test sites, and coalescence of sub-regions into specified zonation areas. The K-means clustering method is used in the classification processes. The applicability of the RZAMH approach to a large area implies that the number of reference sites required to build the reference groups is not of primary importance as long as the reference sites are representative. Therefore, for large areas, the RZAMH approach would be more economical than other conventional methods. The RZAMH approach is probably applicable to all abrupt mass movement hazards including rock falls, landslides, and debris flows.  相似文献   

The Effect of Spatial Heterogeneity in Soil Properties on Erosion Pattern: A Conceptual Model and Computer Simulations     

Alistair Smith  Vladimir Nikora 《Mathematical Geology》2006,38(8):1011-1016

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A sample of 6C radio sources designed to find objects at redshift z > 4 — I. The radio data     

Katherine M.Blundell  SteveRawlings  Stephen A.Eales  Gregory B.Taylor  Alistair D.Bradley 《Monthly notices of the Royal Astronomical Society》1998,295(2):265-279

We describe the selection of a sample of 34 radio sources from the 6C survey from a region of sky covering 0.133 sr. The selection criteria for this sample, hereafter called 6C*, were chosen to optimize the chances of finding radio galaxies at redshift z  > 4. Optical follow-up observations have already led to the discovery of the most distant known radio galaxy at z  = 4.41. We present VLA radio maps and derive radio spectra for all the 6C* objects.  相似文献   

Kinetics of the reactions of hydroxyl radicals with alkyl nitrates and with some oxygen-containing organic compounds studied under simulated atmospheric conditions   总被引：1，自引：0，他引：1  

J. Alistair Kerr  David W. Stocker 《Journal of Atmospheric Chemistry》1986,4(2):253-262

Rate constants have been measured for the reactions of hydroxyl radicals with alkyl nitrates and with some oxygen-containing organic compounds by a competitive technique. Mixtures of synthetic air containing a few ppm of nitrous acid, ethylene and the organic substrate were photolysed in a Teflon bag smog chamber. Based on the value k _HO+C2H₄}=8.1×10^-12 cm³ molecule^-1 s^-1 the following rate constants were obtained for the hydroxyl radical reactions at 750 Torr and at 303 K in units of 10^-12 cm³ molecule^-1: CH₃ONO₂, 0.37±0.09; C₂H₅ONO₂, 0.48±0.20; n-C₃H₇ONO₂, 0.70±0.22; C₂H₅OH, 3.6±0.4; CH₃COCH₃, 0.26±0.08; CH₃CO₂ i-C₃H₇, 3.0±0.8; CH₃CO₂ n-C₃H₇, 2.4±0.2. The results are discussed in relation to the available literature data and the implications of the results are considered in terms of the smog reactivity of these molecules.  相似文献   

Geological setting and tectonic subdivision of the Neoproterozoic orogenic belt of Tuludimtu, western Ethiopia     

Alistair Allen  Gebremedhin Tadesse 《Journal of African Earth Sciences》2003,36(4):329-343

The N–S trending Tuludimtu Belt in the extreme west of Ethiopia has been subdivided into five lithotectonic domains, from east to west, the Didesa, Kemashi, Dengi, Sirkole and Daka domains. The Kemashi, Dengi and Sirkole Domains, forming the core of the belt, contain volcano-sedimentary successions, whilst the Didesa and Daka Domains are gneiss terranes, interpreted to represent the eastern and western forelands of the Tuludimtu Belt. The Kemashi Domain, which consists of an ophiolitic sequence of ultramafic and mafic volcanic and plutonic rocks together with sedimentary rocks of oceanic affinity, is interpreted as oceanic crust and is considered to represent an arc-continent suture zone. The Dengi Domain, composed of mafic to felsic volcanic and plutonic rocks, and a sequence of volcanoclastic, volcanogenic, and carbonate sediments, is interpreted as a volcanic arc. The Sirkole Domain consists of alternating gneiss and volcano-sedimentary sequences, interpreted as an imbricated basement-cover thrust-nappe complex. All the domains are intruded by syn- and post-kinematic Neoproterozoic granitoids. Structural analysis within the Didesa and Daka Domains indicate the presence of pre-Pan African structures, upon which Neoproterozoic deformation has been superimposed. The gneissic rocks of these two domains are regarded as pre-Pan African continental fragments amalgamated to West Gondwana during Neoproterozoic collision events. Unconformably overlying all of the above are a series of tilted but internally undeformed conglomerate–sandstone–shale sequences, regarded as post-accretionary molasse-type deposits, formed during gravitational collapse of the Tuludimtu Belt. The Tuludimtu Belt is interpreted as a collision orogenic belt formed during the assembly of West Gondwana prior to final closure of the Mozambique Ocean.  相似文献