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311.
Equipped to deal with uncertainty in climate and impacts predictions: lessons from internal peer review 总被引:1,自引:0,他引:1
312.
Tony Waltham 《Geology Today》2010,26(4):152-158
Gigantic floods that, for just a few days, had flow rates many times greater than the combined flows of all the other rivers of the world put together. Sounds ridiculous, and it's almost inconceivable, but it's real, and it all happened at the end of the last Ice Age. The water came from Lake Missoula, which exists no more, but the effects are still to be seen in the landscapes, most notably in the vast scablands of eastern Washington. 相似文献
313.
A spatio-temporal model of housing price trends is developed that focuses on individual housing sales over time. The model
allows for both the spatio-temporal lag effects of previous sales in the vicinity of each housing sale, and for general autocorrelation
effects over time. A key feature of this model is the recognition of the unequal spacing between individual housing sales
over time. Hence the residuals are modeled as a first-order autoregressive process with unequally spaced events. The maximum-likelihood
estimation of this model is developed in detail, and tested in terms of simulations based on selected data. In addition, the
model is applied to a small data set in the Philadelphia area. 相似文献
314.
This effort aims to determine the generation source sites in the Luzon Strait for energetic, long-crest, transbasin internal waves (IW) observed in the northern South China Sea (NSCS). The roles of islands distributed on eastern side of the strait, Kuroshio, submarine ridges, shoaling thermocline, and strait configuration played in the IW generation are examined using the cruise data analysis, satellite data interpretation, and dynamical analysis. The islands and channels on eastern side of the strait are excluded from a list of possible IW source sites owing to their unmatched horizontal dimensions to the scale of IW crest line length, and the relative low Reynolds number. The Kuroshio has a potential to be a radiator for the long-crest IW disturbances, meanwhile, the Kuroshio west (east) wing absorbs the eastward (westward) propagating IW disturbance. Namely, the Kuroshio blockades the outside west-east propagating IW disturbances. The 3-D configuration of the Luzon Strait is characterized by a sudden, more than one order widening of the cross-section areas at the outlets on both sides, providing a favorable condition for IW type initial disturbance formation. In the Luzon Strait, the thermocline is featured by a westward shoaling all the year around, providing the dynamical conditions for the amplitude growth (declination) to the westward (eastward) propagating IW type disturbance. Thus,the west slope of western submarine ridge at the western outlet of the Luzon Strait is a high possibility source sites for energetic,long-crest, transbasin Iws in the NSCS. The interpretation results of satellite SAR images during a 13 a period from 1995 to 2007 provide the convincing evidence for the conclusions. 相似文献
315.
Dynamical analysis of mesoscale eddy-induced ocean internal waves using linear theories 总被引:3,自引:1,他引:2
This study aims to explore generation mechanisms of the ocean internal wave using the dynamical analysis methods based on linear theories. Historical cruise measurements and recent synthetic aperture radar (SAR) observations of mesoscale eddies with diameter of several tens of kilometers to hundreds of kilometers show that the internal wave packets with wavelength of hundreds of meters to kilometer exist inside the mesoscale eddies. This coexistence phenomenon and inherent links between the two different scale processes are revealed in the solutions of governing equations and boundary conditions for the internal wave disturbance with a horizontally slowly variable amplitude in a cylindrical coordinate system. The theoretical solutions indicate that the instability of eddy current field provides the dynamical mechanism to internal wave generation. The derived dispersion relation indicates that the internal wave propagation is modified by the eddy current field structure. The energy equation of the internal waves clearly shows the internal wave energy increment comes from the eddy. The theoretical models are used to explain the observation of the mesoscale eddy-induced internal waves off the Norwegian coast. The two-dimensional waveform solution of the anticyclonic eddy-induced internal wave packet appears as ring-shaped curves, which contains the typical features of eddy stream lines. The comparison of theoretical solutions to the structure of the internal wave packets on SAR image shows a good agreement on the major features. 相似文献
316.
Spatial cluster detection techniques are widely used in criminology, geography, epidemiology, and other fields. In particular,
spatial scan statistics are popular and efficient techniques for detecting areas of elevated crime or disease events. The
majority of spatial scan approaches attempt to delineate geographic zones by evaluating the significance of clusters using
likelihood ratio statistics tested with the Poisson distribution. While this can be effective, many scan statistics give preference
to circular clusters, diminishing their ability to identify elongated and/or irregular shaped clusters. Although adjusting
the shape of the scan window can mitigate some of these problems, both the significance of irregular clusters and their spatial
structure must be accounted for in a meaningful way. This paper utilizes a multiobjective evolutionary algorithm to find clusters
with maximum significance while quantitatively tracking their geographic structure. Crime data for the city of Cincinnati
are utilized to demonstrate the advantages of the new approach and highlight its benefits versus more traditional scan statistics. 相似文献
317.
318.
Wisconsinan and Holocene Climate History from an Ice Core at Taylor Dome, Western Ross Embayment, Antarctica 总被引:4,自引:0,他引:4
Eric J. Steig David L. Morse Edwin D. Waddington Minze Stuiver Pieter M. Grootes Paul A. Mayewski Mark S. Twickler & Sallie I. Whitlow 《Geografiska Annaler: Series A, Physical Geography》2000,82(2-3):213-235
Geochemical data and geophysical measurements from a 554-m ice-core from Taylor Dome, East Antarctica, provide the basis for climate reconstruction in the western Ross Embayment through the entire Wisconsinan and Holocene. In comparison with ice cores from central East and West Antarctica, Taylor Dome shows greater variance of temperature, snow accumulation, and aerosol concentrations, reflecting significant variability in atmospheric circulation and air mass moisture content. Extreme aridity during the last glacial maximum at Taylor Dome reflects both colder temperatures and a shift in atmospheric circulation patterns associated with the advance of the Ross Sea ice sheet and accounts for regional alpine glacier retreats and high lake levels in the Dry Valleys. Inferred relationships between spatial accumulation gradients and ice sheet configuration indicate that advance of the Ross Sea ice sheet began in late marine isotope stage 5 or early stage 4. Precise dating of the Taylor Dome core achieved by trace-gas correlation with central Greenland ice cores shows that abrupt deglacial warming at Taylor Dome was near-synchronous with the ∼14.6 ka warming in central Greenland and lags the general warming trend in other Antarctic ice cores by at least 3000 years. Deglacial warming was following by a warm interval and transient cooling between 14.6 and 11.7 ka, synchronous with the Bølling/Allerød warming and Younger Dryas cooling events in central Greenland, and out of phase with the Antarctic Cold Reversal recorded in the Byrd (West Antarctica) ice core. Rapid climate changes during marine isotope stages 4 and 3 at Taylor Dome are similar in character to, and may be in phase with, the Northern Hemisphere stadial–interstadial (Dansgaard–Oeschger) events. Results from Taylor Dome illustrate the importance of obtaining ice cores from multiple Antarctic sites, to provide wide spatial coverage of past climate and ice dynamics. 相似文献
319.
320.
The extent and kinetics of Np(V)O2+ adsorption from dilute aqueous solutions and seawater onto a variety of synthetic and natural solids were determined at 25°C and 1 atm total pressure. Extensive and complex adsorption reactions were found, contrary to speculations in the literature that NpO2+ should behave as a simple monovalent ion with a low affinity for surfaces. When normalized to adsorption per unit solid surface area, the ranking for the synthetic solids was aragonite ? calcite > goethite ? MnO2 ≈ clays. Natural materials generally followed the same behavior patterns as their synthetic counterparts. The dissolved/adsorbed ratio was found to be constant over a wide range (10?13–10?7M) of NpO2+ concentrations. At higher concentrations the extent of adsorption decreased until a solubility limit was reached at approximately 10?5 M.Solution composition had the most significant influence for NpO2+ adsorption on goethite, where much more extensive adsorption occurs in dilute solutions than in seawater. When seawater is added to a dilute solution, extensive desorption of NpO2+ from goethite occurs. Tests conducted on NpO2+ adsorbed on carbonates indicated that it remained in the V oxidation state.There is a growing consensus that Pu dissolved in natural waters also occurs dominantly in the V oxidation state as PuO2+ ion. Consequently, these results for NpO2+ may serve as a guide for Pu behavior when also in the V oxidation state. The fact that most adsorbed Pu is found in the III or IV oxidation states indicates that reduction of Pu may occur subsequent to adsorption in the V oxidation state. 相似文献