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31.
A proposal for a new scenario framework to support research and assessment in different climate research communities 总被引:1,自引:0,他引:1
Detlef P. van Vuuren Keywan Riahi Richard Moss Jae Edmonds Allison Thomson Nebojsa Nakicenovic Tom Kram Frans Berkhout Rob Swart Anthony Janetos Steven K. Rose Nigel Arnell 《Global Environmental Change》2012,22(1):21-35
In this paper, we propose a scenario framework that could provide a scenario “thread” through the different climate research communities (climate change – vulnerability, impact, and adaptation - and mitigation) in order to support assessment of mitigation and adaptation strategies and climate impacts. The scenario framework is organized around a matrix with two main axes: radiative forcing levels and socio-economic conditions. The radiative forcing levels (and the associated climate signal) are described by the new Representative Concentration Pathways. The second axis, socio-economic developments comprises elements that affect the capacity for mitigation and adaptation, as well as the exposure to climate impacts. The proposed scenarios derived from this framework are limited in number, allow for comparison across various mitigation and adaptation levels, address a range of vulnerability characteristics, provide information across climate forcing and vulnerability states and span a full century time scale. Assessments based on the proposed scenario framework would strengthen cooperation between integrated-assessment modelers, climate modelers and vulnerability, impact and adaptation researchers, and most importantly, facilitate the development of more consistent and comparable research within and across these research communities. 相似文献
32.
Timothy M. Dellapenna Mead A. Allison Gary A. Gill Ronald D. Lehman Kent W. Warnken 《Estuarine, Coastal and Shelf Science》2006,69(3-4):519
To address the relative importance of shrimp trawling on seabed resuspension and bottom characteristics in shallow estuaries, a series of disturbance and monitoring experiments were conducted at a bay bottom mud site (2.5 m depth) in Galveston Bay, Texas in July 1998 and May 1999. Based on pre- and post-trawl sediment profiles of 7Be; pore water dissolved oxygen and sulfide concentration; and bulk sediment properties, it was estimated that the trawl rig, including the net, trawl doors, and “tickler chain,” excavate the seabed to a maximum depth of approximately 1.5 cm, with most areas displaying considerably less disturbance. Water column profile data in the turbid plume left by the trawl in these underconsolidated muds (85–90% porosity; <0.25 kPa undrained shear strength) demonstrate that suspended sediment inventories of up to 85–90 mg/cm2 are produced immediately behind the trawl net; an order of magnitude higher than pre-trawl inventories and comparable to those observed during a 9–10 m/s wind event at the study site. Plume settling and dispersion caused suspended sediment inventories to return to pre-trawl values about 14 min after trawl passage in two separate experiments, indicating particles re-settle primarily as flocs before they can be widely dispersed by local currents. As a result of the passage of the trawl rig across the seabed, shear strength of the sediment surface showed no significant increase, suggesting that bed armoring is not taking place and the trawled areas will not show an increase in critical shear stress. 相似文献
33.
34.
Allison L. Steiner Jeremy S. Pal Sara A. Rauscher Jason L. Bell Noah S. Diffenbaugh Aaron Boone Lisa C. Sloan Filippo Giorgi 《Climate Dynamics》2009,33(6):869-892
Coupling of the Community Land Model (CLM3) to the ICTP Regional Climate Model (RegCM3) substantially improves the simulation
of mean climate over West Africa relative to an older version of RegCM3 coupled to the Biosphere Atmosphere Transfer Scheme
(BATS). Two 10-year simulations (1992–2001) show that the seasonal timing and magnitude of mean monsoon precipitation more
closely match observations when the new land surface scheme is implemented. Specifically, RegCM3–CLM3 improves the timing
of the monsoon advance and retreat across the Guinean Coast, and reduces a positive precipitation bias in the Sahel and Northern
Africa. As a result, simulated temperatures are higher, thereby reducing the negative temperature bias found in the Guinean
Coast and Sahel in RegCM3–BATS. In the RegCM3–BATS simulation, warmer temperatures in northern latitudes and wetter soils
near the coast create excessively strong temperature and moist static energy gradients, which shifts the African Easterly
Jet further north than observed. In the RegCM3–CLM3 simulation, the migration and position of the African Easterly Jet more
closely match reanalysis winds. This improvement is triggered by drier soil conditions in the RegCM3–CLM3 simulation and an
increase in evapotranspiration per unit precipitation. These results indicate that atmosphere–land surface coupling has the
ability to impact regional-scale circulation and precipitation in regions exhibiting strong hydroclimatic gradients. 相似文献
35.
Combined Digital Photogrammetry and Time-of-Flight Laser Scanning for Monitoring Cliff Evolution 总被引:4,自引:0,他引:4
Michael Lim David N. Petley Nicholas J. Rosser Robert J. Allison Antony J. Long David Pybus 《The Photogrammetric Record》2005,20(110):109-129
Although cliffs form approximately 75% of the world's coastline, the understanding of the processes through which they evolve remains limited because of a lack of quantitative data on the morphological changes they undergo. In this paper the combination of terrestrial time-of-flight laser scanning with high-resolution digital photogrammetry is examined to generate high-quality data-sets pertaining to the geomorphic processes governing cliff development. The study was undertaken on a section of hard rock cliffs in North Yorkshire, UK, which has been monitored over a 12-month period. High-density, laser-scanned point clouds have been used to produce an accurate representation of these complex surfaces, free from the optical variations that degrade photographic data. These data-sets have been combined with high-resolution photographic monitoring, resampled with the fixed accuracies of the terrestrial laser survey, to generate a new approach to recording the volumetric changes in complex coastal cliffs. This has led to significant improvements in the understanding of the activity patterns of coastal cliffs. 相似文献
36.
Grain Size Analysis and Permeametry for Estimating Hydraulic Conductivity in Engineered Porous Media
Grain size analysis and permeametry are common methods for estimating the hydraulic conductivity (K) of porous media. It is well known that these methods have limited accuracy when they are used to characterize natural sediments. However, hydrogeological research has increasingly introduced technologies dependent on engineered porous media that may be less problematic because complex geologic structures are eliminated in the lab and field-scale packings. The recently introduced Horizontal Reactive Media Treatment Wells (HRX® Wells), for in situ, passive remediation of groundwater is one such example. The HRX Well passively collects groundwater and directs it through a horizontal pipe packed with an engineered porous medium. In this project, grain size analysis was conducted for sand and sand-iron mixtures to estimate K using the 16 algorithms provided in the HydrogeoSieveXL2.3.2 software. The results were compared to K determined by permeametry and a field-scale column, 30 cm long and 25 cm in diameter, representing an HRX Well. The best comparability of K estimates from grain size analysis and permeametry were obtained using the USBR, Slichter, and Shepherd K estimation methods. These also showed good agreement between lab-scale and field-scale K estimations, with reproducibility within the range ±20%. This study shows that laboratory K estimations can be representative across various relevant scales, including the field-scale, for engineered porous media. This finding extends to filter packs, and other engineered porous media design methods by emphasizing and demonstrating one case of accuracy in lab-scale permeability estimation for field-scale implementations. 相似文献
37.
Variations in the stone covers on desert surfaces have implications for the operation of hydrological processes. Some recent attention has been given to the difficulties of identifying and quantifying relevant characteristics of stone covers. Investigation of how such characteristics vary in relation to geological and topographical controls are limited. Results are presented of a field study of the characteristics of stone covers on four lithologies in the late Tertiary to Quaternary basalt plateau of northeast Jordan. Marked variations occur in clast dimensions and the characteristics of sorting between lithologies which are likely to affect hydrological response. A more subtle control, relating to slope conditions, is superimposed on the lithological differences. R- and Q-mode factor analysis identifies groupings within the data, which demonstrate the distinctiveness of different lithologies. Characteristics of the stone covers on sites affected by human occupation are markedly different from undisturbed sites on the same lithology. 相似文献
38.
Rhiannon G. MAYNE Jessica M. SUNSHINE Harry Y. McSWEEN Timothy J. McCOY Catherine M. CORRIGAN Allison GALE 《Meteoritics & planetary science》2010,45(7):1074-1092
Abstract– We investigate the relationship between the petrology and visible–near infrared spectra of the unbrecciated eucrites and synthetic pyroxene–plagioclase mixtures to determine how spectra obtained by the Dawn mission could distinguish between several models that have been suggested for the petrogenesis of Vesta’s crust (e.g., partial melting and magma ocean). Here, we study the spectra of petrologically characterized unbrecciated eucrites to establish spectral observables, which can be used to yield mineral abundances and compositions consistent with petrologic observations. No information about plagioclase could be extracted from the eucrite spectra. In contrast, pyroxene dominates the spectra of the eucrites and absorption band modeling provides a good estimate of the relative proportions of low‐ and high‐Ca pyroxene present. Cr is a compatible element in eucrite pyroxene and is enriched in samples from primitive melts. An absorption at 0.6 μm resulting from Cr3+ in the pyroxene structure can be used to distinguish these primitive eucrites. The spectral differences present among the eucrites may allow Dawn to distinguish between the two main competing models proposed for the petrogenesis of Vesta (magma ocean and partial melting). These models predict different crustal structures and scales of heterogeneity, which can be observed spectrally. The formation of eucrite Allan Hills (ALH) A81001, which is primitive (Cr‐rich) and relatively unmetamorphosed, is hard to explain in the magma ocean model. It could only have been formed as a quench crust. If the magma ocean model is correct, then ALHA81001‐like material should be abundant on the surface of Vesta and the Vestoids. 相似文献
39.
When spatial datasets are overlaid, corresponding features do not always coincide. This may be a result of the datasets having differing quality characteristics, being captured at different scales or perhaps being in different projections or datums. Data integration methods have been developed to bring such datasets into alignment. Although these methods attempt to maintain topological relationships within each dataset, spatial relationships between features in different datasets are generally not considered. The preservation of inter‐dataset topology is a research area of considerable current interest. This research addresses the preservation of topology within a data integration process. It describes the functional models established to represent a number of spatial relationships as observation equations. These are used to provide additional information concerning the relative positions of features. Since many topological relationships are best modelled as inequalities, an algorithm is developed to accommodate such relationships. The method, based on least squares with inequalities (LSI), is tested on simulated and real datasets. Results are presented to illustrate the optimal positioning solutions determined using all of the available information. In addition, updated quality parameters are provided at the level of the individual coordinate, enabling communication of local variation in the resultant quality of the integrated datasets. 相似文献
40.
M. A. Allison C. A. Nittrouer L. E. C. Faria Jr. O. M. Silveira A. C. Mendes 《Geo-Marine Letters》1996,16(1):36-40
Modern and Holocene muddy strata were studied along the shoreline adjacent to the Amazon river mouth using sedimentological, radiochemical, physical, and seismic methods. The present paper is a synthesis of the results, collected during the AmasSeds project, that is used to outline a regional shoreline sediment budget. Erosion of relict Amazon muds in southern Amapa supplies 106 tons yr–1 to the Amazon advective mud stream. Local rivers are sediment-poor (total suspended discharge ~ 1 × 106 tons yr–1), but form depositional sandflats on the shoreface downdrift of the river mouths. Mudflat accumulation in northern Amapa sequesters 106–107 tons yr–1 by tidal-flat aggradation, alongshore mudcape accretion, and sediment trapping by mangroves. The processes temporarily store 1.5 × 108 tons of Amazon mud in January–June. 相似文献