A mathematical model of water and sediment flow in open river channels

A one-dimensional mathematical model of water and sediment flow in open channels is proposed based on the forces influencing a water stream and bottom and stream sediments. The equations of water and sediment flow are closed by the equations of continuity of stream, velocity of particle motion in a stream, and the equation of balance of kinetic energy and moving particles: joint calculation of stream hydraulic characteristics and sediment discharge is performed. Hydraulic resistances are retrieved not from the Chezi formula, but based on the balance of forces and kinetic energy. A sediment discharge is calculated from velocities and the number of moving solid particles instead of empirical relationships whose accuracy is usually low. The model is verified against the data of experiments in hydraulic flumes with glass and sand bottom. Comparison with independent data in the glass flume in a wide range of water discharges and bottom inclinations showed a high accuracy of calculation of hydraulic characteristics (relative error is less than 4%). The experimental data showed that the accuracy of sediment discharge calculated by the model exceeds the accuracy of the calculation using traditional empirical formulas.     

Long-term variability and methods of forecasting dates of ice break-up in the mouth area of the Ob and Yenisei rivers

Long-term characteristics of the onset dates of spring ice phases at hydrological stations in the mouth areas of the Ob and Yenisei rivers for 1936–2006 are obtained. The correlations are analyzed between these dates and the frequency of different synoptic processes over the Atlantic and Eurasia in the fall-winter months, the dates when the accumulated temperatures at meteorological stations in the middle parts of the river basins reach 5, 10, 20, 30, and 40°C, and the dates of the start of ice drift at the upstream sections of the Yenisei. Prognostic relations are suggested and test forecasts of the onset dates of ice phases are verified. The percentage of correct forecasts was 67–86%, which makes it possible to recommend the relations for using in prognostic practice. The forecast lead time ranges from 3 to 110 days.     

Signification de la présence de radon 222 dans les fluides géothermiques

The²²²Rn content of a subterranean fluid depends on the physico-chemical nature of the media through which the fluid passes and on the time spent by the fluid in the various geological formations encountered. Consequently,²²²Rn measurement in a geofluid gives a clue to the subsurface transport conditions of this geofluid. Simple models are proposed for various types of buried structures connected with the surface by a geothermal well; they all lead to the²²²Rn concentration expressed as a function of the flow-rate of the carrier fluid. In real systems, the variations of this concentration with flow-rate would allow the type of structure feading the well to be determined, and, in propitious circumstances, the volume of the possible reservoir to be estimated.     

Application of a Numerical Inverse Laplace Integration Method to Surface Loading on a Viscoelastic Compressible Earth Model

Normal mode approaches for calculating viscoelastic responses of self-gravitating and compressible spherical earth models have an intrinsic problem of determining the roots of the secular equation and the associated residues in the Laplace domain. To bypass this problem, a method based on numerical inverse Laplace integration was developed by Tanaka et al. (2006, 2007) for computations of viscoelastic deformation caused by an internal dislocation. The advantage of this approach is that the root-finding problem is avoided without imposing additional constraints on the governing equations and earth models. In this study, we apply the same algorithm to computations of viscoelastic responses to a surface load and show that the results obtained by this approach agree well with those obtained by a time-domain approach that does not need determinations of the normal modes in the Laplace domain. Using the elastic earth model PREM and a convex viscosity profile, we calculate viscoelastic load Love numbers (h, l, k) for compressible and incompressible models. Comparisons between the results show that effects due to compressibility are consistent with results obtained by previous studies and that the rate differences between the two models total 10–40%. This will serve as an independent method to confirm results obtained by time-domain approaches and will usefully increase the reliability when modeling postglacial rebound.     

Analytical estimations of the efficiency of climate warming prevention by controlled aerosol emissions into the stratosphere

Analytical solutions of globally averaged energy-balance model to estimate the efficiency of controlled forcing on the climate in the result of sulfate aerosol emissions into the stratosphere are obtained. According to obtained results, the sulfate aerosol emissions, needed to prevent the warming, make up from 2 to 12 Mt S/year in the end of the 21st century depending on the anthropogenic impact scenario and aerosol parameters. In the case of the cessation of such compensative emissions of sulfate aerosols, the global temperature increase rate may reach 3 K per decade, that is several times more than values, derived when taking account of greenhouse effect only.     

Stratospheric temperature trends: impact of ozone variability and the QBO

In most climate simulations used by the Intergovernmental Panel on Climate Change 2007 fourth assessment report, stratospheric processes are only poorly represented. For example, climatological or simple specifications of time-varying ozone concentrations are imposed and the quasi-biennial oscillation (QBO) of equatorial stratospheric zonal wind is absent. Here we investigate the impact of an improved stratospheric representation using two sets of perturbed simulations with the Hadley Centre coupled ocean atmosphere model HadGEM1 with natural and anthropogenic forcings for the 1979–2003 period. In the first set of simulations, the usual zonal mean ozone climatology with superimposed trends is replaced with a time series of observed zonal mean ozone distributions that includes interannual variability associated with the solar cycle, QBO and volcanic eruptions. In addition to this, the second set of perturbed simulations includes a scheme in which the stratospheric zonal wind in the tropics is relaxed to appropriate zonal mean values obtained from the ERA-40 re-analysis, thus forcing a QBO. Both of these changes are applied strictly to the stratosphere only. The improved ozone field results in an improved simulation of the stepwise temperature transitions observed in the lower stratosphere in the aftermath of the two major recent volcanic eruptions. The contribution of the solar cycle signal in the ozone field to this improved representation of the stepwise cooling is discussed. The improved ozone field and also the QBO result in an improved simulation of observed trends, both globally and at tropical latitudes. The Eulerian upwelling in the lower stratosphere in the equatorial region is enhanced by the improved ozone field and is affected by the QBO relaxation, yet neither induces a significant change in the upwelling trend.     

On the correlation-regression analysis of thermohaline structure of the northeastern Barents Sea waters

The results of the investigation of thermohaline structure of waters in the northeastern part of the Barents Sea are based on the data of the CTD-survey of hydrophysical testing area (for the regular grid with the resolution of 10 miles), as well as on the data of the stations of the northern part of meridional and quasi-zonal sections up to Novaya Zemlya carried out in August–September 1998 during the 14th cruise of the research vessel Akademik Sergei Vavilov of the Institute of Oceanology of the Russian Academy of Sciences. The methodology includes the analysis of average T, S-characteristics and isopycnic, correlation-regression, and factor analyses of temperature field. The vertical profiles of thermohaline properties in the testing area enable to separate at least five typical elements within the general water stratification. The representative isopycnics for the cores of water masses and transition layers are determined from the averaged T, S-diagrams. The temperature and salinity at the isopycnic surfaces in these layers fit well the linear regression model with rather high level of statistical significance, that indicates a quasi-linear nature of the state equation. The areas of the highest correlations within the water column are separated using the factor analysis of temperature field.     

On the necessity and features of the study of modern natural and man-made geological and hydrometeorological processes in engineering and environmental studies

The limitations of the regulatory framework for the study of hydrometeorological and geological processes in engineering ecological surveys are determined. The necessity of the combination of anthropocentric and biocentric concepts during surveys is justified. The principles of ecologically oriented evaluations of hydrometeorological and geological processes during engineering ecological surveys are defined.     

Reconstruction of the ore-forming system in the Mnogovershinnoe gold-silver deposit (Lower Amur River Region) based on the structure of ore-bearing zones and isotopic studies

The hydrothermal ore-forming paleosystem of the Mnogovershinnoe deposit is reconstructed by defining lithothectonic elements constituting ore-bearing zones with account for their formation mechanisms and positions in the conditional geochronological scale of the hydrothermal activity and isotopic data. The use of lithotectonic elements for deciphering ore genesis events made it possible to take into account both synchronously and successively formed parts of ore bodies, which substantially improved the quality of the reference data for developing a dynamic model of the deposit. The approach proposed for reconstructing the hydrothermal paleosystem of the Mnogovershinnoe deposit may be used for developing models of other ore objects.