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1.
Youhua RAN Xin LI Guodong CHENG Zhuotong NAN Jinxing CHE Yu SHENG Qingbai WU Huijun JIN Dongliang LUO Zhiguang TANG Xiaobo WU 《中国科学:地球科学(英文版)》2021,64(1):62-79
Data scarcity is a major obstacle for high-resolution mapping of permafrost on the Tibetan Plateau(TP).This study produces a new permafrost stability distribution map for the 2010 s(2005–2015)derived from the predicted mean annual ground temperature(MAGT)at a depth of zero annual amplitude(10–25 m)by integrating remotely sensed freezing degree-days and thawing degree-days,snow cover days,leaf area index,soil bulk density,high-accuracy soil moisture data,and in situ MAGT measurements from 237 boreholes on the TP by using an ensemble learning method that employs a support vector regression model based on distance-blocked resampled training data with 200 repetitions.Validation of the new permafrost map indicates that it is probably the most accurate of all currently available maps.This map shows that the total area of permafrost on the TP,excluding glaciers and lakes,is approximately 115.02(105.47–129.59)×10^4 km^2.The areas corresponding to the very stable,stable,semi-stable,transitional,and unstable types are 0.86×10^4,9.62×10^4,38.45×10^4,42.29×10^4,and 23.80×10^4 km^2,respectively.This new map is of fundamental importance for engineering planning and design,ecosystem management,and evaluation of the permafrost change in the future on the TP as a baseline. 相似文献
2.
《Advances in water resources》2004,27(4):311-322
This article is offered to honor Professor George F. Pinder. Its technical contents were motivated by an Eulerian–Lagrangian method that was recently proposed by him and his collaborators. Two one-node-collocation algorithms, which may be used to advance that method are presented. Although they are here discussed for 1-D problems only, one of them has already been generalized to problems in several space variables. Thus, this paper essentially generalizes the above mentioned Eulerian–Lagrangian method of Pinder et al. to problems in several dimensions. Also, the results presented in this paper have a wider interest in water resources studies because they apply to advection diffusive transport processes in general. The methodology used to develop the new algorithms is a unified theory of domain decomposition methods (DDM), recently introduced by the authors and which owes much to George F. Pinder. The results reported in the present paper illustrate, by the way, its application and power. 相似文献
3.
Strong aftershocks have the potential to increase the damage state of the structures due to the damage accumulation. This paper investigates the damage spectra for the mainshock–aftershock sequence-type ground motions with Park–Ang damage index. A method of simulating the mainshock–aftershock sequence-type ground motions is proposed based on the modified form of Bath's law and NGA ground motion prediction equation. The damage spectra are computed using the recorded and simulated sequence-type ground motions, and the effects of period of vibration, strength reduction factor, site condition, seismic sequence, damping ratio and post-yield stiffness on damage spectra are studied statistically. The results indicate that the effect of aftershock on structural damage is significant and recorded sequence-type ground motions may underestimate the damage of long-period structures due to the incompleteness of dataset. A simplified equation is proposed to facilitate the application of damage spectra in the seismic practice for mainshock–aftershock sequence-type ground motions. 相似文献
4.
In this paper we present a reliable algorithm, the homotopy perturbation method, to construct numerical solutions of the space–time fractional advection–dispersion equation in the form of a rapidly convergent series with easily computable components. Fractional advection–dispersion equations are used in groundwater hydrology to model the transport of passive tracers carried by fluid flow in a porous medium. The fractional derivatives are described in the Caputo sense. Some examples are given. Numerical results show that the homotopy perturbation method is easy to implement and accurate when applied to space–time fractional advection–dispersion equations. 相似文献
5.
In this study, a new model is developed for the aseismic design of a periodic viaduct when the pile–soil–structure interaction is considered. To account for the influence of the pile–soil–structure interaction, a wavenumber domain boundary element method (WDBEM) model for the periodic pile row supporting the viaduct is developed using the sequence Fourier transform as well as the boundary element method for the elastic medium. By using the WDBEM model for the pile row, the transfer matrices for the beams and piers, the joint conditions at the beam–beam–pier (BBP) junction as well as the periodicity condition for the viaduct, the wavenumber domain response of the periodic viaduct to spatially harmonic waves is determined. Based on the wavenumber domain response of the viaduct, the space-domain response of the viaduct to an arbitrary seismic wave can be obtained by invoking the inverse sequence Fourier transform method. Numerical results show that when the periodic viaduct is exposed to the spatially harmonic wave, resonances may occur at the bounding frequencies of the passbands of the characteristic waves of the viaduct. Also, it is found that the coincidence between the traveling seismic wave and characteristic waves of the viaduct will generate additional resonant frequencies located in passbands of the characteristic waves. 相似文献
6.
Meir Abelson Amotz Agnon Ahuva Almogi-Labin 《Earth and Planetary Science Letters》2008,265(1-2):33-48
The Eocene/Oligocene boundary, at about 33.5 Myr ago, marks the transition from ‘greenhouse-’ to ‘icehouse-world’, accompanied by a sudden cooling of ocean bottom-water. We show that this global event is simultaneous with a deep rooted mantle process: an abrupt suppression of the Iceland plume triggered rapid deepening of the Greenland–Scotland Ridge (GSR) — the sill moderating deep circulation between the Nordic seas and North Atlantic. Striking coincidence of several sets of events reflects the abrupt suppression of the Iceland plume and a rapid removal of its influence on the nearby Reykjanes Ridge (RR): 1) A sudden segmentation of the paleo-RR seen on seafloor magnetic anomalies, 2) a drop in spreading rate of the North Atlantic, 3) a transition from thick to normal oceanic crust, and 4) a rapid deepening and accelerated subsidence of the GSR, inferred from the sedimentary record of DSDP site 336. The plume suppression and the concomitant GSR deepening coincide with the initiation of North Atlantic Deep Water (NADW) at the Eocene/Oligocene (E/O) transition, attested by onset of drift sedimentation in the Faroe–Shetland Channel (FSC), the deepest spill-point on the GSR, and in the North Atlantic, the Feni Drift. These processes have influenced global deepwater composition and temperature as indicated by the striking correlation with the jump in global δ18O (> 1‰) measured on benthic foraminifers that reflects the E/O global cooling, and with enrichment of unradiogenic Nd isotopes in the southeastern Atlantic and Southern Ocean. The initiation of Atlantic thermohaline circulation at that time is inferred from the abrupt split between planktonic and benthic δ18O, indicating the building of ocean-water stratification. This scenario is further corroborated by a reversal in benthic δ18O at the late Oligocene, coincident with the renewal of vigorous Iceland plume some 25 Myr ago, causing a considerable retardation in NADW fluxes. The plume renewal is inferred from the emergence of the Iceland plateau, the transition to oblique-unsegmented RR axis, the cessation in deepening of the GSR, and rapid increase in spreading rate of the North Atlantic. These events coincide with decreasing difference in planktonic–benthic in global δ18O by the late Oligocene. All these inferences suggest the role of the NADW sourced at the Nordic seas to form background cooler conditions in the long time scale since the early Oligocene, or to form permanent conditions of invigorated thermohaline circulation that forces CO2 trap in the oceans. 相似文献
7.
In this paper, we use the inertial coupling relation as a similarity model for the air–sea boundary layer, to predict the 10-m drag coefficient. Excellent agreement with the commonly used statistical relationship of Garratt (1992) is found for a fully developed growing wind wave sea with a constant inertial drag coefficient, KI = 1.5 × 10–3. This suggests that the inertial coupling model can be used to realistically predict the 10 m drag coefficient under more general wind wave conditions.Acknowledgements The paper was completed while JATB was a Fellow at the Hanse-Wissenschaftskolleg in Delmenhorst, Germany, in July and August 2004. The comments of two anonymous reviewers are gratefully acknowledged. 相似文献
8.
Motovilov Yu. G. Golosov S. D. Datsenko Yu. S. Zverev I. S. Puklakov V. V. Fashchevskaya T. B. 《Water Resources》2020,47(5):751-762
Water Resources - An Information–Modeling Complex has been developed for the information support of managerial decision making in the field of rational use, protection, and restoration of... 相似文献
9.
《Advances in water resources》1999,23(3):271-301
Primary variable switching appears as a promising numerical technique for variably saturated flows. While the standard pressure-based form of the Richards equation can suffer from poor mass balance accuracy, the mixed form with its improved conservative properties can possess convergence difficulties for dry initial conditions. On the other hand, variable switching can overcome most of the stated numerical problems. The paper deals with variable switching for finite elements in two and three dimensions. The technique is incorporated in both an adaptive error-controlled predictor–corrector one-step Newton (PCOSN) iteration strategy and a target-based full Newton (TBFN) iteration scheme. Both schemes provide different behaviors with respect to accuracy and solution effort. Additionally, a simplified upstream weighting technique is used. Compared with conventional approaches the primary variable switching technique represents a fast and robust strategy for unsaturated problems with dry initial conditions. The impact of the primary variable switching technique is studied over a wide range of mostly 2D and partly difficult-to-solve problems (infiltration, drainage, perched water table, capillary barrier), where comparable results are available. It is shown that the TBFN iteration is an effective but error-prone procedure. TBFN sacrifices temporal accuracy in favor of accelerated convergence if aggressive time step sizes are chosen. 相似文献
10.
A. M. Fetisova R. V. Veselovskiy F. Scholze Yu. P. Balabanov 《Izvestiya Physics of the Solid Earth》2018,54(1):150-162
The results of detailed paleomagnetic studies in seven Upper Permian and Lower Triassic reference sections of East Europe (Middle Volga and Orenburg region) and Central Germany are presented. For each section, the coefficient of inclination shallowing f (King, 1955) is estimated by the Elongation–Inclination (E–I) method (Tauxe and Kent, 2004) and is found to vary from 0.4 to 0.9. The paleomagnetic directions, corrected for the inclination shallowing, are used to calculate the new Late Permian–Early Triassic paleomagnetic pole for the East European Platform (N = 7, PLat = 52.1°, PLong = 155.8°, A95 = 6.6°). Based on this pole, the geocentric axial dipole hypothesis close to the Paleozoic/Mesozoic boundary is tested by the single plate method. The absence of the statistically significant distinction between the obtained pole and the average Permian–Triassic (P–Tr) paleomagnetic pole of the Siberian Platform and the coeval pole of the North American Platform corrected for the opening of the Atlantic (Shatsillo et al., 2006) is interpreted by us as evidence that ~250 Ma the configuration of the magnetic field of the Earth was predominantly dipolar; i.e., the contribution of nondipole components was at most 10% of the main magnetic field. In our opinion, the hypothesis of the nondipolity of the geomagnetic field at the P–Tr boundary, which has been repeatedly discussed in recent decades (Van der Voo and Torsvik, 2001; Bazhenov and Shatsillo, 2010; Veselovskiy and Pavlov, 2006), resulted from disregarding the effect of inclination shallowing in the paleomagnetic determinations from sedimentary rocks of “stable” Europe (the East European platform and West European plate). 相似文献
11.
A comprehensive analysis of Kamchatka seismicity for the period 2005–2007 using the regional catalog
We characterize the Kamchatka seismicity for the period 2005–2007. Regional catalogs of Kamchatka earthquakes were used to
develop 2D distributions of parameters of background seismicity. The characteristics we consider include the activity A
10, the slope of the recurrence curve γ, the parameters involved in the methods RTL, ΔS, and the “Z-function”, as well as the control of earthquake clustering. We have detected the space-time agreement between the anomalies
exhibited by several parameters. 相似文献
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13.
《Advances in water resources》1999,23(3):229-237
It can be very time consuming to use the conventional numerical methods, such as the finite element method, to solve convection–dispersion equations, especially for solutions of large-scale, long-term solute transport in porous media. In addition, the conventional methods are subject to artificial diffusion and oscillation when used to solve convection-dominant solute transport problems. In this paper, a hybrid method of Laplace transform and finite element method is developed to solve one- and two-dimensional convection–dispersion equations. The method is semi-analytical in time through Laplace transform. Then the transformed partial differential equations are solved numerically in the Laplace domain using the finite element method. Finally the nodal concentration values are obtained through a numerical inversion of the finite element solution, using a highly accurate inversion algorithm. The proposed method eliminates time steps in the computation and allows using relatively large grid sizes, which increases computation efficiency dramatically. Numerical results of several examples show that the hybrid method is of high efficiency and accuracy, and capable of eliminating numerical diffusion and oscillation effectively. 相似文献
14.
We present a unified model of the air–sea boundary layer, which takes account of the air–sea momentum exchange across the
sea surface. The recognition of the importance of the velocity shears in the water (which comprise a frictional shear and
the Stokes shear due to the wave motion) in determining the sea surface roughness is a distinctive feature of the analysis,
which leads to a prediction of the Charnock constant (α) in terms of two independent parameters, namely the wave age and the ratio of the Stokes shear to the Eulerian shear in the
water. This expression is used to interpret the large observational variability of the Charnock constant. The 10-m drag coefficient
can also be expressed using similar reasoning, and the introduction of a relation in which the ratio of the frictional shear
in the water to the frictional shear in the air decreases with the friction velocity yields predictive relations for the variation
of the 10-m drag coefficient at very high wind speeds both in the open ocean and in wind–wave tanks. The physical interpretation
of this relation is that the production of spray essentially returns momentum from the ocean to the atmosphere, and this process
becomes progressively more important as the wind speed increases. 相似文献
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Laryunin O. A. Kurkin V. I. Berngardt O. I. Salimov B. G. Podlesnyi A. V. 《Geomagnetism and Aeronomy》2019,59(1):101-104
Geomagnetism and Aeronomy - Vertical ionograms often contain traces of reflections that cannot be attributed to any type of the sporadic Es layer and are classified as anomalous reflections.... 相似文献
18.
The rainfall–runoff modelling being a stochastic process in nature is dependent on various climatological variables and catchment characteristics and therefore numerous hydrological models have been developed to simulate this complex process. One approach to modelling this complex non-linear rainfall–runoff process is to combine the outputs of various models to get more accurate and reliable results. This multi-model combination approach relies on the fact that various models capture different features of the data, and hence combination of these features would yield better result. This study for the first time presented a novel wavelet based combination approach for estimating combined runoff The simulated daily output (Runoff) of five selected conventional rainfall–runoff models from seven different catchments located in different parts of the world was used in current study for estimating combined runoff for each time period. Five selected rainfall–runoff models used in this study included four data driven models, namely, the simple linear model, the linear perturbation model, the linearly varying variable gain factor model, the constrained linear systems with a single threshold and one conceptual model, namely, the soil moisture accounting and routing model. The multilayer perceptron neural network method was used to develop combined wavelet coupled models to evaluate the effect of wavelet transformation (WT). The performance of the developed wavelet coupled combination models was compared with their counterpart simple combination models developed without WT. It was concluded that the presented wavelet coupled combination approach outperformed the existing approaches of combining different models without applying input WT. The study also recommended that different models in a combination approach should be selected on the basis of their individual performance. 相似文献
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F. L. M. Diermanse K. M. De Bruijn J. V. L. Beckers N. L. Kramer 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(3):637-652
During flood events, breaching of flood defences along a river system can have a significant reducing effect on downstream water levels and flood risks. This paper presents a Monte Carlo based flood risk framework for policy decision making, which takes this retention effect into account. The framework is developed to estimate societal flood risk in terms of potential numbers of fatalities and associated probabilities. It is tested on the Rhine–Meuse delta system in the Netherlands, where floods can be caused by high flows in the Rhine and Meuse rivers and/or high sea water levels in the North Sea. Importance sampling is applied in the Monte Carlo procedure to increase computational efficiency of the flood risk computations. This paper focuses on the development and testing of efficient importance sampling strategies for the framework. The development of an efficient importance sampling strategy for river deltas is more challenging than for non-tidal rivers where only discharges are relevant, because the relative influence of river discharge and sea water level on flood levels differs from location to location. As a consequence, sampling methods that are efficient and accurate for one location may be inefficient for other locations or, worse, may introduce errors in computed design water levels. Nevertheless, in the case study described in this paper the required simulation time was reduced by a factor 100 after the introduction of an efficient importance sampling method in the Monte Carlo framework, while at the same time the accuracy of the Monte Carlo estimates were improved. 相似文献