ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles  (22,389)
  • Wiley  (13,594)
  • Springer  (8,795)
  • 1995-1999  (11,743)
  • 1990-1994  (9,093)
  • 1940-1944  (1,553)
  • Geography  (22,389)
Collection
  • Articles  (22,389)
Years
Year
Journal
  • 101
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 47 (1992), S. 259-265 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary THETAPLOT is a diagram useful for the display and analysis of atmospheric thermodynamic soundings, particularly in relation to conditionally and convectively instable summertime weather situations. The basic coordinates of THETAPLOT are the equivalent potential temperature and the negative logarithm of pressure. The body of the diagram contains families of curves of constant potential temperature, mixing ratio and temperature. From any given sounding, three curves are plotted on the diagram: 1) Theta-ed, the equivalent potential temperature of air saturated at its dew point temperature; 2) Theta-e, equivalent potential temperature; and 3) Theta-es, the saturated equivalent potential temperature. The winds are plotted along the margin of the diagram.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 102
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 49 (1992), S. 187-207 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary This paper is concerned with the simulation of deep convection for the CCOPE 19 July 1981 case study. Clark's three-dimensional (3D) cloud model modified to use the bulk water parameterization scheme of Lin et al. has been used in the simulation of the CCOPE 19 July 1981 case in coarse mesh, fine mesh, and interactive grid nested schemes, respectively. Comparisons with observations show this 3D grid nested cloud model is capable of both capturing both the dynamic and microphysical properties of the cloud. In the nested grid fine mesh model simulation, the timing and mode of cloud growth, the diameter of liquid cloud, the cloud top rate of rise, the maximum cloud water content, and the altitude of first radar echo are consistent with observations. The simulated thunderstorm begins to dissipate, after precipitation reaches the ground as indicated by the decreasing values of maximum updraft and maximum liquid cloud water content, and ends as a precipitating anvil as was observed in the actual thunderstorm. The model precipitation developed through ice phase processes consistent with the analysis of observations from the actual thunderstorm. Qualitative comparisons of the actual radar RHIs with simulated reflectively patterns from the 3D model show remarkable similarity, especially after the mature stage is reached. Features of the actual RHI patterns, such as the weak echo region, upshear anvil bulge, strong upwind reflectivity gradients, and the upwind outflow region near the surface are reproduced in the simulation. Comparison of the actual radar PPIs with horizontal cross sections of radar reflectivity simulated by the 3D model, however, show modest differences in the storm size with the 3D simulated thunderstorm being 1–2 km longer in the west-east direction than the actual thunderstorm. The model-predicted maximum updraft speed is smaller than the 2D model-predicted maximum updraft speed, but still greater than what was observed. Comparisons among the nested grid fine mesh model (MB), nested grid coarse mesh model (MA), fine mesh model (FM), coarse mesh model (CM), and 2D model results previously published show that the nested grid fine mesh model (MB) gives the best simulation result. The various 3D model simulation results are generally similar to each other except for the difference in the domain maximum values. The domain maximum values in the fine mesh models (MB and FM) are generally higher than the coarse mesh models as a result of averaging over a smaller area.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 103
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary The Penn State University/National Center for Atmospheric Research (PSU/NCAR) mesoscale model is a widely used research tool that has been applied in a wide variety of real-data, mesoalpha-scale applications. Recently a nonhydrostatic version of this model has been developed by Dudhia (1993). It is the purpose of this paper to illustrate the capabilities of this modeling system by describing four examples of mesobeta-scale simulations: two of the cases involve maritime processes and two deal with continental weather events. All utilize fully three-dimensional sets of initial conditions that are based on real data, both standard data and from special measurements programs. One case employs the model in a data-assimilation configuration, wherein Newtonian relaxation terms are used in the equations to assimilate data from a variety of platforms. This example of nonhydrostatic four-dimensional data assimilation (FDDA) is performed for the purpose of generating a dynamically consistent four-dimensional data-set, however the same procedure can be used for model initialization. The first case, described in section 2, involves the simulation of a coastal front that forms offshore near the western edge of the Gulf Stream. In the second case, described in section 3, the model is used in the FDDA mode to define the mesobeta-scale windfield over the complex terrain of the region around Grand Canyon, Arizona. In sections 4 and 5 will be described the mesobeta-scale structure of cold fronts, one within a marine cyclone, and another near the Rocky Mountains.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 104
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary Hydrostatic and nonhydrostatic simulation models are employed to study the intensification of a terrain drag-induced dryline. The study develops a multi-stage theory for the evolution of the dryline including the concentration of potential vorticity accompanying meso-gamma scale dryline “bulges”. The numerical simulations indicate three fundamental stages of dryline intensification all of which are either directly or indirectly a result of the terrain-drag on the mid/upper-tropospheric jet stream by the Front Range of the Colorado Rocky Mountains. The first stage involves the downward momentum flux accompanying a large amplitude hydrostatic mountain wave which induces a downslope windstorm along the lee slopes. The surge of momentum (i.e., the dry, warm air associated with the downslope windstorm) propagates down the leeslope and modifies an existing weak dryline boundary. As the downslope windstorm initiates an undular bore along the lee slopes, the high momentum gradient which propagates downstream accompanying the bore, as well as the strong lower tropospheric sinking motions ahead of the bore, contract the scale of the surface moisture boundary between the dry air from above the leeslope and the moist air over the High Plains. This process further strengthens the dryline. The second stage involves the coupling of the terrain drag-induced along-stream ageostrophic front within the midtroposphere to the boundary layer through a thermally-indirect circulation. As the along-stream ageostrophic circulation intensifies within the middle troposphere down-stream from the mountain wave, sinking air parcels originating above 40 kPa descend to below 60 kPa over the High Plains where surface pressures are, only ∼85 kPa. These descending air parcels within the upstream branch of the along-stream ageostrophic thermally-indirect circulation contain high values of momentum and very low dewpoint values. As the planetary boundary layer (PBL) deepens due to surface warming during the morning hours, momentum and dry air from the midtropospheric along-stream ageostrophic front are entrained into the PBL. This process amplifies the bore-induced hydrostatic dryline bulge via low-level ageostrophic confluence. Finally, regions of low Richardson number (arising from strong vertical shears) within the amplifying midtropospheric along-stream ageostrophic thermally-indirect circulation become preferred regions for the development of non-hydrostatic evanescent internal gravity waves. These waves are embedded within the hydrostatic along-stream front above the low-level dryline and are accomapanied by very significant values of vertical momentum flux which act to focus the meso-gamma scale structure of the dryline into smaller scale bulges where low-level winds and vorticities are very high. This meso-gamma scale process follows the hydrostatic tilting and vortex tube stretching which creates meso-beta scale maxima of mid-lower tropospheric vorticity. The turbulent momentum fluxes accompanying wavebreaking within the nonhydrostatic dryline bulge create very large (i.e., stratospheric values of) potential vorticity near 70 kPa due to the nonconservation of potential vorticity on isentropic surfaces.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 105
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 49 (1992), S. 229-254 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary A nonhydrostatic numerical simulation of a tropical cyclone is performed with explicit representation of cumulus on a meso-β scale grid and for a brief period on a meso-γ scale grid. Individual cumulus plumes are represented by a combination of explicit resolution and a 1.5 level closure predicting turbulent kinetic energy (TKE). The results demonstrate a number of expected and unexpected important scale interaction processes. Within the central core of the developing cyclone, meso-β convective regions grow and breakdown into propagating inertiagravity waves throughout the lifecycle of the cyclone. In the early stages, the amplitude of pressure fluctuations associated with the meso-β scale convection exceed the central pressure of the cyclone and strongly modulate its intensity. With each meso-β scale pulsation, the cyclone core increases in strength, measured by the central pressure deficit. The increasingly strong inertial frequency of the storm core acts to increasingly trap the convection induced heating within the core by balancing the tangential wind against the low central pressure, before the meso-β scale convection breaks down and sends the warmth away as a propagating wave. Eventually, the slow manifold's amplitude exceeds the amplitude of the meso-β scale oscillations and a stable eye region is formed. As inertial instability increases, increasingly high thermal warmth can be protected in the core, allowing persistent subsidence to form and to clear out the cyclone eye. On the outside of the eye wall, strong inertial stability gradients in the troposphere cause convective warming to split the inflow to the eye wal! and spawn outwardly propagating inertia gravity waves. These waves carry away all of the heating forced by convection that is not inertially trapped by the eye wall and act as a moderating influence on storm intensity. Inertia gravity waves are also spawned in the stratosphere at the top of the eye wall by the revolution of asymmetric cumulus structures. In all instances, the tropospheric waves are coupled to the propagating stratospheric waves which both move at 35 ms−1, although there are many instances where the stratospheric waves seem to have no tropospheric counterpart. Hence the anvil top forcing and low level breakdown are linked. The outwardly propagating inertia gravity waves act to initiate outer bands of convection. This initiation is with the assistance of low level boundary layer variations of density related to previous convection and to virga falling from the anvil which moistens and destabilizes the mid levels ofθ e minimum. The convection initiated by these waves does not move substantially outward with the wave, although may appear to develop outward discontinuously.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 106
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 50 (1992), S. 75-88 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary The set of fully compressible nonhydrostatic equations governing a broad spectrum of atmospheric motion was transformed fromz coordinates to sigma coordinates under a hydrostatic base state. The hydrostatic base state may be either time-independent, such as a hydrostatic balance with-out motion or with motion such as a thermal wind balance, or time-dependent such as might be obtained from the result of integrating a hydrostatic model. The transformed set of equations can be used to predict and study all scales of at mospheric phenomena. The set of perturbation equations was also derived under the same condition. The computational sensitivity in computation of pressure gradient force in sigma coordinate can be improved by computing the pressure gradient interms of perturbations under a certain hydrostatic state. The hydrostatic regional spectral model developed by Juang and Kanamitsu (1991) was modified to be a nonhydrostatic spectral model based on the nonhydrostatic equations in sigma coordinates with time-dependent hydrostatic base states. A semi-implicit time integration scheme was used. Two experiments were performed to test this nonhydrostatic spectral model with acceptable results.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 107
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 50 (1992), S. 61-73 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary Most finite-difference numerical weather prediction models employ vertical discretizations that are staggered, and are low-order (usually second-order) approximations for the important terms such as the derivation of the geopotential from the hydrostatic equation, and the calculation of the vertically integrated divergence. In a sigma-coordinate model the latter is used for computing both the surface pressure change and the vertical velocity. All of the above-mentioned variables can diminish the accuracy of the forecast if they are not calculated accurately, and can have an impact on related quantities such as precipitation. In this study various discretization schemes in the vertical are compared both in theory and in practice. Four different vertical grids are tested: one unstaggered and three staggered (including the widely-used “Lorenz” grid). The comparison is carried out by assessing the accuracy of the grids using vertical numerics that range from second-order up to sixth-order. The theoretical part of the study examines how faithfully each vertical grid reproduces the vertical modes of the governing equations linearized with a basic state atmosphere. The performance of the grids is evaluated for 2nd, 4th and 6th-order numerical schemes based on Lagrange polynomials, and for a 6th-ordercompact scheme. Our interpretation of the results of the theoretical study is as follows. The most important result is that the order of accuracy employed in the numerics seems to be more significant than the choice of vertical grid. There are differences between the grids at second-order, but these differences effectively vanish as the order of accuracy increases. The sixth-order schemes all produce very accurate results with the grids performing equally well, and with the compact scheme significantly outperforming the Lagrange scheme. A second major result is that for the number of levels typically used in current operational forecast models, second-order schemes (which are used almost universally) all appear to be relatively poor, for other than the lowest modes. The theoretical claims were confirmed in practice using a large number (100) of forecasts with the Australian Bureau of Meteorology Research Centre's operational model. By comparing “test” model forecasts using the four grids and the different orders of numerics with very high resolution “control” model forecasts, the results of the theoretical study seem to be corroborated.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 108
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 50 (1992), S. 127-142 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary Convective to planetary scale processes govern the motion and structure of tropical storms. A model with a high resolution and a large domain is required for accurate prediction of a storm's track and intensity. A series of integrations are performed using a primitive equation model and an initial state that defines a tropical storm that later developed into a hurricane in the real atmosphere. Increasing the horizontal resolution or domain of the model improves the forecast track. However only the increase in the horizontal resolution produces a better hurricane structure. Banded structure in the vertical motion field, asymmetries in the low tropospheric winds similar to those observed and upper tropospheric cyclonic outflow develop in high horizontal resolution experiments. It is shown that horizontal advection and pressure gradient terms produce wind tendencies in the low troposphere that displace the vortex in the observed direction. A high pressure area surrounding the central low pressure area appears in the upper troposphere. Around this high pressure area large pressure gradients develop that induce outflow winds in the distal storm area.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 109
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 50 (1992), S. 105-126 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary In this paper we present some recent work on typhoon prediction with a high resolution global model. The emphasis of this paper is on typhoon recurvature. Here we include examples of successful typhoon recurvature track forecasts made from a very high resolution global spectral model. The main objective of this study however is to go beyond the forecasts, i.e. to interrogate the history tapes and to diagnose residue-free budgets of the divergence and vorticity. The premise of this paper is that the recurvature of the typhoons depends on both the usual advection of vorticity by the layer mean winds and the advection of divergence in the outflow layers of the storm. The region immediately outside the heavy rain area of the storm experiences large values of divergent outflows which contribute a significant advection of divergence. Through the Dine's compensation this region must, in consort, experience an enhancement of low level convergence and of deep convection, thus contributing to the storm motion. We distinguish two facets of storm motion and recurvature, one based on the conventional steering that invokes the advection of vorticity by a vertical integrated flow, the other is the generation mechanism proposed here. During recurvature the storm appears to move in a direction which is influenced by the rotational and the divergent flow dynamics. Increased vertical resolution in the outflow layer is shown to resolve stronger amplitudes in the outflow layer divergence and thus to contribute to improved forecasts of recurvature. A number of processes seem to simultaneously evolve, these include the strong advection of divergence part of the wind, enhancement of cumulus convection over this region, an enhancement of lower tropospheric convergence, generation of vorticity of the lower troposphere and the attendant recurvature.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 110
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 50 (1992), S. 143-163 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary A number of forecast experiments were performed in order to assess the capability of reproducing, by means of a limited-area numerical model, the highly structured mesoscale circulations occurring in the Po Valley of Northern Italy during a north-westerly cold front passage across the Alpine chain, with particular attention to the modelling of the effects of organized convection. The case-study occurred during summer 1987 and the model used throughout was the 1989 version of the UB/NMC Limited Area Model (University of Belgrade, National Meteorological Centre of Washington). The model was integrated both with eta, η, and sigma, ϑ, as vertical coordinates and ECMWF initialized analyses were always used as initial conditions. ECMWF initialized analysis or operational forecast fields were also used for updating in time the lateral boundary conditions. Experiments show qualitative and quantitative agreement with observations, both in upper-air geopotential height fields, in MSLP and in cumulated precipitation. Several modelling issues were also investigated, e.g. sensitivity of the results to horizontal and vertical model resolution and to the influence of the lateral boundaries poitioning, finding large effects of the latter on quantitative precipitation fields. Difficulties in modelling very localized mesoscale phenomena, e.g. organized convective thunderstorms in the Po Valley and Alpine North Foehn in the Milan area, were generally encounted.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 111
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 50 (1992), S. 165-174 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary In this paper we present a methodology for evaluating rain rates from a mix of satellite and surface based observations. The component data sets include the outgoing longwave radiation (OLR), microwave radiometric data from the special sensor microwave imager (SSM/I) and surface raingauge data from the World Weather Watch. We have noted some deficiencies in the SSM/I algorithm-based rain rate over land areas; the OLR-based rain rates exhibit a larger lateral spread and lower intensities than the observed rainfall structures. The proposed combined method assimilates these three data sets to provide improved fields of global tropical rainfall.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 112
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 50 (1992), S. 175-187 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary The Kuo-type cumulus parameterization and rainfall rate scheme is extended by including the outgoing longwave radiation (OLR), the local time rate of change of OLR, and the horizontal Laplacian of OLR to include the additional source of mesoscale moisture supply. The extended scheme remains simple and efficient. A series of 5-day forecasts of the 1979 monsoon for the tropical belt between the Arabian Sea and the western Pacific Ocean show improvement in the 3-day forecast in the daily accumulated precipitation in both the amount and location. Further RMS error analyses indicate that using OLR and the Laplacian of OLR also produces a significant improvement in a 3-day forecast. Additional tests of the extended scheme for the 1987 and 1988 monsoons produced consistent and characteristic areal rainfall rates in the tropics. The improvement in the “OLR model” forecasts is attributed to the improved skill of OLR forecast in the forecast model as the RMS errors for 5 consecutive days in the 6 experimental forecasts are smaller than those of the 3 control forecasts.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 113
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 50 (1992), S. 189-195 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary A special analytical solution is derived for the classical orographic configuration of two-dimensional, stratified, linear, non-hydrostatic and dry model (without friction and Coriolis force). The well-known differential equation for the vertical velocity involves the vertical distribution of the Scorer parameterl 2(z) and in this casel 2 is specified such that the lower atmosphere has a stable duct near the surface and is capped by a layer which acts as a good reflector. Examination of the solution for the vertical amplitude in the vicinity of singularities indicates the dominant lee wavelength and observations confirm that in comparable settings resonant trapped gravity waves develop in the lee of mountains. Comparison with a real atmospheric lee-wave events gives good predictions for the wavelength and wave drag, but, as in other linear models, the amplitude is underestimated.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 114
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 50 (1992), S. 237-238 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 115
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 50 (1992), S. 231-236 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary In this paper we combine chaotic theory with statistics to present three forecast models: a model of equal distance ind-dimensional phase space, a mode regression model of twelve units and a model of neighborhood model regression. Many experiments show that all these models can generate accurate forcasts.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 116
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 51 (1993), S. 1-24 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary Nonlinear interactions and feedbacks in frontal dynamics are studied with two-dimensional quasigeostrophic, semigeostrophic and primitive equation models for given cases of moderate surface cold fronts. According to the degree of approximation these feedbacks are in effect as a result of geostrophic and ageostrophic advection configuring the further frontal development and the associated energy-transfers between the geostrophic and the ageostrophic scales. The most prominent feedback processes, including the feedback connected with the ageostrophic along-front windv ag , are theoretically reviewed. In cases of smallv ag values, their effects on form and horizontal scale of the frontal secondary circulation are discussed by comparing the products of different model versions and the cross-frontal spectral analysis of the ageostrophic wind fields. To scrutinize the role played by thev ag -field, further experiments were based on a hierarchy ofv ag -substitutes parameterized by the momentum equation of the crossfrontal winddu/dt=fv ag . Tentative results show the tendency towards very localized effects.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 117
    Electronic Resource
    Electronic Resource
    Springer
    Journal of geographical systems 1 (1999), S. 277-303 
    ISSN: 1435-5949
    Keywords: Key words: Higher education ; geodemographics ; participation rates ; JEL classification: C80 ; I21 ; I28 ; J11
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract. Higher education in England has expanded rapidly in the last ten years with the result that currently more than 30% of young people go on to university. Expansion is likely to continue following the recommendations of a national committee of inquiry (the Dearing Committee). The participation rate is known to vary substantially among social groups and between geographical areas. In this paper the participation rate is calculated using a new measure, the Young Entrants Index (YEI), and the extent of variation by region, gender and residential neighbourhood type established. The Super Profiles geodemographic system is used to facilitate the latter. This is shown to be a powerful discriminator and to offer great potential as an alternative analytical approach to the conventional social class categories, based on parental occupation, that have formed the basis of most participation studies to date.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 118
    Electronic Resource
    Electronic Resource
    Springer
    Journal of geographical systems 1 (1999), S. 305-321 
    ISSN: 1435-5949
    Keywords: Key words: GIS, urban systems model, land use – transportation model, traffic analysis zone ; JEL classification: R11, R14, R41
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract. The main purpose of this paper is to explore a possible integration for the entire transportation modeling procedure – from data inventory to future demand forecasting – by implementing integrated land use and transportation models with a geographic information system (GIS). In order to make an integrated, procedural modeling system possible, Land Use and Transportation modeling system with GIS (LUTGIS) has been developed and presented in this paper.  There are four sub-systems in LUTGIS: (1) a data inventory system, (2) a traffic analysis zone generation system, (3) an integrated land use and transportation modeling system, and (4) a graphic user interface (GUI) system. Since the main target of this paper is to explore a possible way to create a viable system, LUTGIS integrates currently available and user-friendly computing technologies. For both transportation planners and administrative decision-makers, such an operable system is very desirable for sharing information so they may arrive at a consensus through the use of LUTGIS, an integrated land use and transportation modeling system.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 119
    Electronic Resource
    Electronic Resource
    Springer
    Papers in regional science 72 (1993), S. 405-423 
    ISSN: 1435-5957
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Economics
    Notes: Abstract This paper investigates the distribution chain of foodstuffs from the factory or port to the customer, from the point of view of the different energy inputs needed. Connections between the changes in the structure of the distribution system and changes in energy consumption are looked for. A model is developed for an energy audit of a distribution system. It is used to calculate the energy requirements of the Finnish food distribution system in the recent past, at present, and for a partial rearrangement of the system, i.e., with home deliveries replacing shopping trips by car. All parts of the distribution system have become more energy intensive as the structure of the distribution system has changed over time. The items related to households stand out as the largest energy consumers. The home delivery example shows an energy conservation potential worth pursuing further.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 120
    Electronic Resource
    Electronic Resource
    Springer
    Papers in regional science 72 (1993), S. 369-387 
    ISSN: 1435-5957
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Economics
    Notes: Abstract This paper provides an overview of the evolution of interregional disparities in Europe and in the United States in recent decades, considering also the changes that economic integration over the 1990s and beyond may bring. The assumptions of the existing paradigms on differential regional change are placed in perspective, by relating them to past and ongoing changes in interregional disparities. Data on the European (EC) and United States cases are analyzed, providing insights into past performance and into its possible causes. A final section then discusses the characteristics of regional inversion processes, and their potential for reducing interregional disparities as economic integration advances. These macro-level characteristics are related to micro-level processes in which innovation (technological, organizational, institutional) plays a central role, allowing less developed regions to bypass a rigid or static domestic spatial division of labor through the inversion process.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 121
    ISSN: 1435-5957
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Economics
    Notes: Abstract In this paper, we investigate the role of input-output data sources in regional econometric input-output models. While there has been a great deal of experimentation focused on the accuracy of alternative methods for estimating regional inputoutput coefficients, little attention has been directed to the role of accuracy when the input-output system is nested within a broader accounting framework. The issues of accuracy were considered in two contexts, forecasting and impact analysis focusing on a model developed for the Chicago region. We experimented with three input-output data sources: observed regional data, national input-output, and randomly generated inputoutput coefficients. The effects of different sources of input-output data on regional econometric input-output models revealed that there are significant differences in results obtained in both forecast and impact analyses. The adjustment processes inherent in the econometric input-output system did not mask the differences imbedded in input-output tables derived from different data sources. Since applications of these types of models involve both impact and forecasting exercises, there should be strong motivation for basing the syste on the most accurate set of input-output accounts.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 122
    Electronic Resource
    Electronic Resource
    Springer
    Papers in regional science 75 (1996), S. 177-199 
    ISSN: 1435-5957
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Economics
    Notes: Abstract Japan National Railways went private in 1987, the first of many national railways to do so, and the Japanese experience could provide lessons to other nations. This paper evaluates the effects of Japan National Railways' Privatization on labor productivity and employment in the passenger sectors. The main data was obtained from the Annual Rail Statistics of both the Ministry of Transport and Japan National Railways. Quantitative methods such as labor productivity models were used to evaluate the effects of privatization. Large private railways, which are considered the most efficient railways in Japan, are often compared to privatized Japan Railways. Major findings are as follows: First, Japan Railways still have 20% more employees than large private railways. Second, current productivity differences between Japan Railways and large private railways appear in station and maintenance activities. Third, reduction in employment during the transitional periods of privatization greatly contributed to increases in the productivity of Japan Railways. Fourth, it is not clear whether or not productivity differences among regional Japan Railways have been decreasing since privatization. Finally, the effect of privatization on productivity growth was about 29%. Moreover, even if productivity increases, safety is not compromised, with serious accidents clearly being unrelated to productivity growth.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 123
    Electronic Resource
    Electronic Resource
    Springer
    Papers in regional science 75 (1996), S. 433-440 
    ISSN: 1435-5957
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Economics
    Notes: Abstract This paper explicitly incorporates monopsony market structure into the Weber-Moses's one-output, two-input triangular location model and reexamines the location invariance principle. It will be shown that this principle need not hold if the imperfection of input markets prevails. This is contrary to the conventional wisdom.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 124
    Electronic Resource
    Electronic Resource
    Springer
    Papers in regional science 75 (1996), S. 135-153 
    ISSN: 1435-5957
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Economics
    Notes: Abstract The relationship between urbanization and level of income has been the subject of considerable theoretical debate and empirical study for many years. However, little recent work has been done to determine whether or not previous findings still hold, and there has been even less multi-country analysis to explore the degree of generality. Analysis of data for metropolitan areas in the United States from 1970 to 1990 indicates per capita income increases directly with population size. For states of the United States and 113 countries for 1960 and 1980 a strong positive relationship exists and holds temporally between level of per capita Gross Domestic Product and percent of the population that is urban.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 125
    Electronic Resource
    Electronic Resource
    Springer
    Papers in regional science 75 (1996), S. 201-235 
    ISSN: 1435-5957
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Economics
    Notes: Abstract Foreign direct investment in the United States is an integral part of the competition among global industrial core regions. Most foreign investment in the U.S. originates in Europe, Canada, and Japan. Acquisition rather than new plant establishment is the favored mode of investment and the interregional supply of potential acquisition candidates constrains foreign investors' locational choices. This paper provides an analysis of the location of foreign employment in 15 disaggregated sectors across U.S. states in 1990. The results show that foreign firms concentrate employment in existing regions of production. Foreign investments in most raw materials processing sectors particularly favor these places. Some decentralization has occurred in several sectors, especially food, paper, chemicals and petroleum, rubber and plastics, stone, clay and glass products, and primary metals. Other significant determinants of location include labor force characteristics and certain regional preferences. No evidence was found in our analysis of disaggregate sectors that foreign investors avoid strong unions more than their domestic counterparts.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 126
    Electronic Resource
    Electronic Resource
    Springer
    Papers in regional science 75 (1996), S. 265-291 
    ISSN: 1435-5957
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Economics
    Notes: Abstract Drawing from flexible production literature on industrial networks, this research pays particular attention to the socially embedded nature of firm linkages in a distribution sector. The empirical study of Chinese-owned computer wholesale firms within Los Angeles County shows that the presence of ethnic identity plays a significant role in the internal operation and external transactions of Chinese firms. Ethnic relations facilitate interactions within the ethnic group, producing a closely knit ethnic network within the industry. The heavy reliance on ethnic networks also has led Chinese firms to a notable geographical separation from the remaining firms in the same sector.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 127
    Electronic Resource
    Electronic Resource
    Springer
    Papers in regional science 75 (1996), S. 351-374 
    ISSN: 1435-5957
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Economics
    Notes: Abstract Producer services employment has grown rapidly within advanced economies in recent years. The bases of demand related to this growth are not well understood by regional scientists. A common view is that this growth is largely attributable to cost-driven factors and vertical disintegration processes on the part of producer service users. This paper demonstrates that cost-driven externalization is not the most important force underlying growth in demand for producer services. The need for specialized knowledge is by far the most important factor behind producer services demand, combined with a variety of other cost, quasi-cost, and non-cost-driven forces.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 128
    Electronic Resource
    Electronic Resource
    Springer
    Papers in regional science 75 (1996), S. 463-481 
    ISSN: 1435-5957
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Economics
    Notes: Abstract This paper focuses on the dynamic relations between Spain's principal regional labor markets. An economic base mechanism, some of whose assumptions are redefined, is postulated as the essential behavior hypothesis. The bifurcation hypothesis is resolved having regard to the necessary condition of cointegration between the basic sector and the regional aggregate, using series with quarterly periodicity in this case. The identified bases, which need not coincide in each region, allow a dynamic inter-regional model to be built using vector autoregression with an error correction mechanism. The results are a step towards the spatial disaggregation of Spain's labor market and reveal singular dynamic relationships.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 129
    Electronic Resource
    Electronic Resource
    Springer
    Papers in regional science 75 (1996), S. 501-524 
    ISSN: 1435-5957
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Economics
    Notes: Abstract This paper aims at positioning spatial development at the crossroads of the conflicting needs for spatial mobility and spatial sustainability. Such tensions have explicitly been recognized in recent local, national and international policy documents. A reconciliation of such antagonistic driving forces in our modern network economy requires a solid theoretical framework in which the relevant force fields are depicted and in which the uncertainties inherent in any attempt at steering human behavior in space are explicitly recognized. This requires an analytical framework in which relevant scenarios are systematically projected on a model structure describing the above mentioned force field. This paper will try to offer an operational methodology for coping with the above mentioned conflicting issues in planning for sustainable spatial development. Particular attention will be given to the spatial scale of analyzing sustainable development. The methodology will be illustrated by presenting empirical results from a case study undertaken in the western part of the Netherlands, the so called Randstad.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 130
    Electronic Resource
    Electronic Resource
    Springer
    Papers in regional science 78 (1999), S. 21-45 
    ISSN: 1435-5957
    Keywords: JEL classification: C52, R10, R12, R14, R39 ; Key words:New economic geography, spatial statistics, spatial modeling, methodology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Economics
    Notes: Abstract. Krugman states that “Regional science is not a unified subject. It is best described as a collection of tools.” Unfortunately such a perspective fails to fully acknowledge theoretical dimensions of the accompanying refocusing on geographic expressions of economic linkages, such as those highlighted in spatial externalities specifications. Such promulgated aspects of the spatial economic landscape relate to map pattern, and certainly the spatial statistics and spatial econometrics theory that accompanies it, as well as the underlying substantive theory garnered from a variety of sources. The principal implication is other than “loose- jointed, do-the-best-you-can theorizing”.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 131
    Electronic Resource
    Electronic Resource
    Springer
    Papers in regional science 78 (1999), S. 111-116 
    ISSN: 1435-5957
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Economics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 132
    Electronic Resource
    Electronic Resource
    Springer
    Papers in regional science 78 (1999), S. 117-118 
    ISSN: 1435-5957
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Economics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 133
    Electronic Resource
    Electronic Resource
    Springer
    Papers in regional science 78 (1999), S. 157-177 
    ISSN: 1435-5957
    Keywords: JEL classification: R1, R12 ; Key words:Central place theory, choice rules, generalised Voronoi diagrams, market areas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Economics
    Notes: Abstract. Although a variety of modifications of classical central place theory has been proposed, one area that remains unexplored is the effect of relaxing the nearest centre assumption for the purchase of a specified basket of goods within a given hierarchical level. This article examines the effect of such a relaxation on central place market areas by using higher-order Voronoi diagrams. When used to model market areas, higher-order Voronoi diagrams can be interpreted as overlapping and probabilistic regions. These diagrams construct market areas based on the assumption that consumers choose from a set of $k (k = 1, 2, \ldots, n)$ nearest centres of the same hierarchical level. If consumers are assumed to be indifferent between the k centres, the appropriate market areas are given by the order-k Voronoi diagram. In this case, it is shown that sales potentials are consistent with those that result when the nearest centre assumption is in effect. If consumers are assumed to have a preference for nearer centres, market areas are defined by the ordered, order-k Voronoi diagram. This situation generates sales potentials which can vary between centres.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 134
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 51-63 
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A basic problem in hydrology is computing confidence levels for the value of the T-year flood when it is obtained from a Log Pearson III distribution in terms of estimated mean, estimated standard deviation, and estimated skew. In an important paper Chowdhury and Stedinger [1991] suggest a possible formula for approximate confidence levels, involving two functions previously used by Stedinger [1983] and a third function, λ, for which asymptotic estimates are given. This formula is tested [Chowdhury and Stedinger, 1991] by means of simulations, but these simulations assume a distribution for the sample skew which is not, for a single site, the distribution which the sample skew is forced to have by the basic hypothesis which underlies all of the analysis, namely that the maximum discharges have a Log Pearson III distribution. Here we test these approximate formulas for the case of data from a single site by means of simulations in which the sample skew has the distribution which arises when sampling from a Log Pearson III distribution. The formulas are found to be accurate for zero skew but increasingly inaccurate for larger common values of skew. Work in progress indicates that a better choice of λ can improve the accuracy of the formula.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 135
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 94-94 
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 136
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 95-114 
    ISSN: 1436-3259
    Keywords: Soil moisture ; time scale ; non-Gaussian ; colored-noise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Large-scale fields of soil moisture are forced by atmospheric precipitation and radiative forcing. When these forcing factors are themselves influenced by surface and soil moisture processes, the result is a nonlinear land-atmosphere system with inherent feedback mechanisms that may strongly modulate variability in climate. Given such feedbacks, simple randomness in the forcing factors may be manifested as a complex statistical signature in the surface hydrology. In this paper, we investigate the impacts of non-Gaussian and colored-noise on the probability distribution of soil moisture resulting from the statistical-dynamical land-atmosphere interaction model of Rodriguez-Iturbe et al. (1991). Persistence of hydroclimatologic anomalies as characterized by the correlation time scale of soil moisture is discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 137
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 115-127 
    ISSN: 1436-3259
    Keywords: Rainfall-runoff modeling ; transfer response ; dynamic non-linear models ; normal and gamma observational distribution ; predictive performance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The rainfall-runoff modeling is very useful for forecasting purposes. A good methodology for forecasting the future stream flow is a key requirement for designers and operators of water resources systems. A compromise between conceptual and classical time series modeling is applied to model the relationship between rainfall and runoff. The dynamic nonlinear model is composed of a probability distribution describing the observation, a link function relating its mean to the so called state parameters and a system of equations defining the evolution of these parameters. Its Bayesian nature permits to take into account subjective information, making forward intervention, defining monitoring schemes and introducing smoothing facilities. An application using the data of Fartura river's basin is reported. The assessment of the prior distribution is discussed and the predictive performance of the linear and the non-linear models is reported.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 138
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 129-143 
    ISSN: 1436-3259
    Keywords: Stochastic analysis ; perturbation methods ; unsaturated transport ; heterogeneous porous media
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Within the framework of stochastic theory and the spectral perturbation techniques, three-dimensional dispersion in partially saturated soils with a finite correlation scale of log-hydraulic conductivity is analyzed. The effects of spatial variability of the moisture distribution parameter on the asymptotic spreading behavior of a unsaturated solute plume are assessed. This is accomplished by comparing two asymptotic macrodispersivities and two variance of solute concentration, obtained for a constant moisture content and spatially varied moisture, respectively.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 139
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 65-93 
    ISSN: 1436-3259
    Keywords: Nonparametric ; Monte Carlo ; precipitation ; weather
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A nonparametric resampling technique for generating daily weather variables at a site is presented. The method samples the original data with replacement while smoothing the empirical conditional distribution function. The technique can be thought of as a smoothed conditional Bootstrap and is equivalent to simulation from a kernel density estimate of the multivariate conditional probability density function. This improves on the classical Bootstrap technique by generating values that have not occurred exactly in the original sample and by alleviating the reproduction of fine spurious details in the data. Precipitation is generated from the nonparametric wet/dry spell model as described in Lall et al. [1995]. A vector of other variables (solar radiation, maximum temperature, minimum temperature, average dew point temperature, and average wind speed) is then simulated by conditioning on the vector of these variables on the preceding day and the precipitation amount on the day of interest. An application of the resampling scheme with 30 years of daily weather data at Salt Lake City, Utah, USA, is provided.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 140
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 255-266 
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract It has been observed that the field biodegradation rates for soluble hydrocarbon plumes are significantly smaller than the aerobic rates observed in the laboratory. It is believed that this difference is related to the fact that in the field oxygen and hydrocarbon must be mixed before the biodegradation reaction can occur, and that the effective degradation rate is controlled by the actual, not mean, concentrations of oxygen and hydrocarbon. In this work, we present a conceptual model of oxygen-mixing limited biodegradation, which indicates that the effective degradation rate should depend on the cross correlation between the oxygen and hydrocarbon concentration fluctuations. This is followed by a development of a rigorous, field-scale model.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 141
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 229-254 
    ISSN: 1436-3259
    Keywords: Model validation ; analysis of uncertainty ; model verification ; quality assurance ; system identification ; model calibration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The development and use of models for predicting exposures are increasingly common and are essential for many risk assessments of the United States Environmental Protection Agency (EPA). Exposure assessments conducted by the EPA to assist regulatory or policy decisions are often challenged to demonstrate their “scientific validity”. Model validation has thus inevitably become a major concern of both EPA officials and the regulated community, sufficiently so that the EPA's Risk Assessment Forum is considering guidance for model validation. The present paper seeks to codify the issues and extensive foregoing discussion of validation with special reference to the development and use of models for predicting the impact of novel chemicals on the environment. Its preparation has been part of the process in formulating a White Paper for the EPA's Risk Assessment Forum. Its subject matter has been drawn from a variety of fields, including ecosystem analysis, surface water quality management, the contamination of groundwaters from high-level nuclear waste, and the control of air quality. The philosophical and conceptual bases of model validation are reviewed, from which it is apparent that validation should be understood as a task of product (or tool) design, for which some form of protocol for quality assurance will ultimately be needed. The commonly used procedures and methods of model validation are also reviewed, including the analysis of uncertainty. Following a survey of past attempts at resolving the issue of model validation, we close by introducing the notion of a model having maximum relevance to the performance of a specific task, such as, for example, a predictive exposure assessment.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 142
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 303-321 
    ISSN: 1436-3259
    Keywords: Simulation ; hydrograph rise and recession ; rainfall process ; probability distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A model is developed for annual low flow hydrographs. Its two primary components reflect the fact that hydrologic processes during streamflow rise (function of water input) and recession (function of basin storage) are different. Durations of periods of rise (wet intervals) and recession (dry intervals) are modelled by discrete probability distributions — negative binomial for dry intervals and negative binomial or modified logarithmic series for wet intervals depending on goodness of fit. During wet intervals, the total inflow is modelled by the lognormal distribution and daily amounts are allocated according to a pattern-averaged model. During dry intervals, the flow recedes according to a deterministic-stochastic recession model. The model was applied to three Canadian basins with drainage area ranging from 2210 to 22000 km2 to generate 50 realizations of low flow hydrographs. The resulting two standard-error confidence band for the simulated probability distribution of annual minimum 7-day flows enclosed the probability distribution estimated from the observed record. A sensitivity analysis for the three basins revealed that in addition to the recession submodel, the most important submodel is that describing seasonality. The state of the basin at the beginning of the low flow period is of marginal importance and the daily distribution of input is unimportant.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 143
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 267-295 
    ISSN: 1436-3259
    Keywords: Space/time processes ; stochastic analysis ; regression model ; solute contents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A regression model is used to study spatiotemporal distributions of solute content ion concentration data (calcium, chloride and nitrate), which provide important water contamination indicators. The model consists of three random and one deterministic components. The random space/time component is assumed to be homogeneous/stationary and to have a separable covariance. The purely spatial and the purely temporal random components are assumed to have homogenous and stationary increments, respectively. The deterministic component represents the space/time mean function. Inferences of the random components involve maximum likelihood and semi-parametric methods under some restrictions on the data configuration. Computational advantages and modelling limitations of the assumptions underlying the regression model are discussed. The regression model leads to simplifications in the space/time kriging and cokriging systems used to obtain space/time estimates at unobservable locations/instants. The application of the regression model in the study of the solute content ions was done at a global scale that covers the entire region of interest. The variability analysis focuses on the calculation of the spatial direct and cross-variograms and the evaluation of correlations between the three solute content ions. The space/time kriging system is developed in terms of the space direct and cross-variograms, and allows the separate estimation of the regression model components. Maps of these components are then obtained for each one of the three ions. Using the estimates of the purely spatial component, spatial dependencies between the ions are studied. Physical causes and consequences of the space/time variability are discussed, and comparisons are made with previous analyses of the solute content dataset.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 144
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 323-330 
    ISSN: 1436-3259
    Keywords: Kolmogorov-Smirnov test ; identification of periodic component ; goodness-of-fit test for white noise ; periodogram ; residuals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A modified version of the widely used Kolmogorov-Smirnov (K-S) test of null hypothesis is constructed, that a given time series is Gaussian white noise, against the alternative hypothesis that the time series contains an added or multiplicative deterministic-periodic component of unspecified frequency. The usual KS test is treated as a special case. The proposed test is more powerful than the ordinary K-S test in detecting extreme (low or high) hidden periodicities. Computational procedure necessary for implementation are also given.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 145
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 297-302 
    ISSN: 1436-3259
    Keywords: Perturbation ; conservative chemical ; velocity variance ; eulerian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A recursive perturbation solution to the eulerian transport problem for a conservative solute in a random conductivity field is reported. The stochastic concentration is given to arbitrary order inσ ν, the variance of fluctuating velocity. The result gives the stochastic concentration as a perturbation to the deterministic concentration for constant mean flow. The closed form solution is easy to implement numerically via FFT.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 146
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 331-348 
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Under the assumption that local solute dispersion is negligible, a new general formula (in the form of a convolution integral) is found for the arbitrary k-point ensemble moment of the local concentration of a solute convected in arbitrary m spatial dimensions with general sure initial conditions. From this general formula new closed-form solutions in m=2 spatial dimensions are derived for 2-point ensemble moments of the local solute concentration for the impulse (Dirac delta) and Gaussian initial conditions. When integrated over an averaging window, these solutions lead to new closed-form expressions for the first two ensemble moments of thevolume-averaged solute concentration and to the corresponding concentration coefficients of variation (CV). Also, for the impulse (Dirac delta) solute concentration initial condition, the second ensemble moment of thesolute point concentration in two spatial dimensions and the corresponding CV are demonstrated to be unbound. For impulse initial conditions the CVs for volume-averaged concentrations axe compared with each other for a tracer from the Borden aquifer experiment. The point-concentration CV is unacceptably large in the whole domain, implying that the ensemble mean concentration is inappropriate for predicting the actual concentration values. The volume-averaged concentration CV decreases significantly with an increasing averaging volume. Since local dispersion is neglected, the new solutions should be interpreted as upper limits for the yet to be derived solutions that account for local dispersion; and so should the presented CVs for Borden tracers. The new analytical solutions may be used to test the accuracy of Monte Carlo simulations or other numerical algorithms that deal with the stochastic solute transport. They may also be used to determine the size of the averaging volume needed to make a quasi-sure statement about the solute mass contained in it.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 147
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 349-368 
    ISSN: 1436-3259
    Keywords: Data assimilation ; Kalman filter ; Square root filter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The Kalman filter algorithm can be used for many data assimilation problems. For large systems, that arise from discretizing partial differential equations, the standard algorithm has huge computational and storage requirements. This makes direct use infeasible for many applications. In addition numerical difficulties may arise if due to finite precision computations or approximations of the error covariance the requirement that the error covariance should be positive semi-definite is violated. In this paper an approximation to the Kalman filter algorithm is suggested that solves these problems for many applications. The algorithm is based on a reduced rank approximation of the error covariance using a square root factorization. The use of the factorization ensures that the error covariance matrix remains positive semi-definite at all times, while the smaller rank reduces the number of computations and storage requirements. The number of computations and storage required depend on the problem at hand, but will typically be orders of magnitude smaller than for the full Kalman filter without significant loss of accuracy. The algorithm is applied to a model based on a linearized version of the two-dimensional shallow water equations for the prediction of tides and storm surges. For non-linear models the reduced rank square root algorithm can be extended in a similar way as the extended Kalman filter approach. Moreover, by introducing a finite difference approximation to the Reduced Rank Square Root algorithm it is possible to prevent the use of a tangent linear model for the propagation of the error covariance, which poses a large implementational effort in case an extended kalman filter is used.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 148
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 369-395 
    ISSN: 1436-3259
    Keywords: Random fields ; diagrams ; perturbation ; non-local ; effective conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract This work presents a stochastic diagrammatic theory for the calculation of the effective hydraulic conductivity of heterogeneous media. The theory is based on the mean-flux series expansion of a log-normal hydraulic conductivity medium in terms of diagrammatic representations and leads to certain general results for the effective hydraulic conductivity of three-dimensional media. A selective summation technique is used to improve low-order perturbation analysis by evaluating an infinite set of diagrammatic terms with a specific topological structure that dominates the perturbation series. For stochastically isotropic media the selective summation yeilds the anticipated exponential expression for the effective hydraulic conductivity. This expression is extended to stochastically anisotropic media. It is also shown that in the case of non homogeneous media the uniform effective hydraulic conductivity is replaced by a non-local tensor kernel, for which general diagrammatic expressions are obtained. The non-local kernel leads to the standard exponential behavior for the effective hydraulic conductivity at the homogeneous limit.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 149
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 175-191 
    ISSN: 1436-3259
    Keywords: Flow through porous media ; random network ; macro-permeability ; micro-geometry ; statistical mechanics ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract This paper presents an analysis of Hagen-Poiseulle flow through plane random anisotropic networks of interconnected channels. Macroscopic permeability tensor of the network is expressed in terms of statistico-geometrical characteristics like the degree of anisotropy in channel orientations, average co-ordination number of the network and first two moments of channel length distribution. Analytical results are illustrated and verified using numerical analysis of flow in a simulated random network. The emphasis of the paper is on the effects of anisotropy on distributions of flow rates in channels. It is shown that, due to anisotropy the maximum flow rate generally occurs in channels that are not aligned along the direction of the macroscopic pressure gradient.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 150
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 253-254 
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 151
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 241-251 
    ISSN: 1436-3259
    Keywords: Sedimentation ; Large Reservoirs ; Markov Chains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Sediment deposition and its accumulation in a large resorvoir depends on the inflow and reservoir storage content, respectively. Because of this fact it is possible to model the cumulative deposition of sediment as an additive process defined on a bivariate Markov chain. Using the bivariate Markov chain model the mean and variance of the cumulative deposition of John Martin Reservoir, Colorado, U.S.A. are estimated and compared with observed sedimentation data.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 152
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 295-308 
    ISSN: 1436-3259
    Keywords: Risk-based design ; uncertainty analysis ; hydraulic design ; bridge ; culvert
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract For a proposed highway bridge or culvert, the total cost to the public during its expected service life includes capital investment on the structures, regular operation and maintenance costs, and various flood related costs. The flood related damage costs include items such as replacement and repair costs of the highway bridge or culvert, flood plain property damage costs, users costs from traffic interruptions and detours, and others. As the design discharge increases, the required capital investment increases but the corresponding flood related damage costs decrease. Hydraulic design of a bridge or culvert using a riskbased approach is to choose among the alternatives the one associated with the least total expected cost. In this paper, the risk-based design procedure is applied to pipe culvert design. The effect of the hydrologic uncertainties such as sample size and type of flood distribution model on the optimal culvert design parameters including design return period and total expected cost are examined in this paper.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 153
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 5 (1991), S. 31-44 
    ISSN: 1436-3259
    Keywords: Radar rainfall ; gage rainfall ; parameter uncertainty ; Bayesian estimation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract In Seo and Smith (this issue), a set of estimators was built in a Bayesian framework to estimate rainfall depth at an ungaged location using raingage measurements and radar rainfall data. The estimators are equivalent to lognormal co-kriging (simple co-kriging in the Gaussian domain) with uncertain mean and variance of gage rainfall. In this paper, the estimators are evaluated via cross-validation using hourly radar rainfall data and simulated hourly raingage data. Generation of raingage data is based on sample statistics of actual raingage measurements and radar rainfall data. The estimators are compared with lognormal co-kriging and nonparametric estimators. The Bayesian estimators are shown to provide some improvement over lognormal co-kriging under the criteria of mean error, root mean square error, and standardized mean square error. It is shown that, if the prior could be assessed more accurately, the margin of improvement in predicting estimation variance could be larger. In updating the uncertain mean and variance of gage rainfall, inclusion of radar rainfall data is seen to provide little improvement over using raingage data only.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 154
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 483-510 
    ISSN: 1436-3259
    Keywords: Conceptual-stochastic models ; shot noise ; streamflow simulation ; time aggregation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A conceptual-stochastic approach to short time runoff data modelling is proposed, according to the aim of reproducing the hydrological aspects of the streamflow process and of preserving as much as possible the dynamics of the process itself. This latter task implies preservation of streamflow characteristics at higher scales of aggregation and, within a conceptual framework, involves compatibility with models proposed for the runoff process at those scales. At a daily time scale the watershed response to the effective rainfall is considered as deriving from the response of three linear reservoirs, respectively representing contributions to streamflows of large deep aquifers, with over-year response lag, of aquifers which run dry by the end of the dry season and of subsurface runoff. The surface runoff component is regarded as an uncorrelated point process. Considering the occurrences of effective rainfall events as generated by an independent Poisson process, the output of the linear system represents a conceptually-based multiple shot noise process. Model identification and parameter estimation are supported by information related to the aggregated runoff process, in agreement to the conceptual framework proposed, and this allows parameter parsimony, efficient estimation and effectiveness of the streamflow reproduction. Good performances emerged from the model application and testing made with reference to some daily runoff series from Italian basins.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 155
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 511-521 
    ISSN: 1436-3259
    Keywords: Runoff events ; arrival times ; partial duration series ; arid areas ; Israel ; probabilistic modeling ; Pearson III distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Present descriptions of arrival times of runoff events are based upon modeling of interarrival intervals. Maintaining the traditional assumption that arrival times are independent random variables, these times can be directly described through a continuous distribution fitted to recorded data. A case study for the arid Negev region in Israel indicates that the Pearson type III distribution satisfactorily achieves this goal. The direct description can apply nonuniform functions, respond to multi-modal distributions, and be extended to regional modeling.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 156
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 27-45 
    ISSN: 1436-3259
    Keywords: Rainfall ; Precipitation ; Forecasting ; Real-time ; Modeling ; Simulation ; Stochastic ; Prediction ; Sampling ; Measurement ; Updating ; Filtering ; Estimation ; Short-term
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 157
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 81-88 
    ISSN: 1436-3259
    Keywords: Helmholtz equation ; random parameter ; semiconfined aquifer ; groundwater flow ; boundary element method ; perturbation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract With the aid of perturbation technique a boundary element procedure is developed for solution of two-dimensional Helmholtz equation with a random parameter of small variability. The perturbation boundary element method does not require specification of probability density function of the parameter but only its mean and standard deviation. The method is used to analyze steady-state groundwater flows in a horizontal shallow semiconfined aquifer (homogeneous and isotropic) of probabilistic properties. To illustrate the applicability of the method, a simple numerical example is presented. As the nature of perturbation method suggests, the developed method is valid only when the perturbed value of the parameter is of a small order.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 158
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 5 (1991), S. 255-260 
    ISSN: 1436-3259
    Keywords: Drought ; probability ; stochastic process ; water management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract What constitutes a comprehensive description of drought, a description forming a basis for answering why a drought occurred is outlined. The description entails two aspects that are “naturally” coupled, named physical and economic, and treats the set of hydrologic measures of droughts in terms of their multivariate distribution, rather than in terms of a collection of the marginal distributions.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 159
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 47-54 
    ISSN: 1436-3259
    Keywords: Bivariate density ; dependence structure ; correlation coefficient ; Farlie-Gumbel-Morgenstern density ; Farlie polynomial density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Certain bivariate densities constructed from marginals have recently been suggested as models of hydrologic variates such as rainfall intensity and depth. It is pointed out that (i) these densities belong to the families of the Farlie-Gumbel-Morgenstern densities and the Farlie polynomial densities, which have been extensively studied in the statistical literature, and that (ii) these densities have a limited potential applicability in hydrology since they can model only weakly associated variates, whose product-moment correlationR is within the range |R|≤1/3, under the first family of densities, and |R|≤1/2 under the second family.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 160
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 69-80 
    ISSN: 1436-3259
    Keywords: Hydrology ; global circulation models ; statistics ; climate change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Many researchers use outputs from large-scale global circulation models of the atmosphere to assess hydrological and other impacts associated with climate change. However, these models cannot capture all climate variations since the physical processes are imperfectly understood and are poorly represented at smaller regional scales. This paper statistically compares model outputs from the global circulation model of the Geophysical Fluid Dynamics Laboratory to historical data for the United States' Laurentian Great Lakes and for the Emba and Ural River basins in the Commonwealth of Independent States (C.I.S.). We use maximum entropy spectral analysis to compare model and data time series, allowing us to both assess statistical predictabilities and to describe the time series in both time and frequency domains. This comparison initiates assessments of the model's representation of the real world and suggests areas of model improvement.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 161
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 223-238 
    ISSN: 1436-3259
    Keywords: River Flow Model ; Time Series ; Autoregressive
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The Non-Gaussian Multicomponent model for river flow (NGM) of Vandewiele and Dom is modified in order to facilitate maximum likelihood estimation. It is also generalized so that a wider variety of river flows at a diversity of time steps can be modeled. This model is applied to two basins in Belgium and France with very different areas, both at monthly and weekly time scale. Results on the quality of forecasting and simulation (especially simulation of low and high flow volumes) are compared with those of classical Periodic Autoregressive models (PAR). Results with NGM are always better, in most cases considerably better. This is due to the fact that NGM models explicitly take into consideration the presence of so called flow components, like baseflow and direct flow recession, which are phenomena well known to hydrologists.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 162
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 167-182 
    ISSN: 1436-3259
    Keywords: Crossing theory ; exponential autocovariance model ; discrete time series ; Weibull distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract An expression is derived for the probability distribution of excursion lengths above a fixed level, for the specific case of a discrete random process sampled from an underlying, continuous normal process with exponential autocovariance function. The expression can be integrated numerically for small excursion lengths, and used with time-series simulations to qualitatively reveal the form of the distribution. Such computations indicate that excursions lengths are well approximated by a Weibull distribution to at least the 0.95 probability value. The fit improves with increasing fixed level, and with decreasing time constant of the process. In addition, an expression is given for the expected number of crossings of a fixed level, analogous to well known formulae used in estimating expected values for the cases of a continuous process and a discrete stepped process.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 163
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 183-190 
    ISSN: 1436-3259
    Keywords: Markov chains ; seasonality ; multivariate gamma distributions ; weighted sums of gammas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A Markov chain{X t }, which has been useful for modelling in hydrology, can be specified by the Laplace transform (LT) of the conditional p.d.f. ofX t+1 givenX t =x t , which is assumed to be of the ‘exponential’ formH(θ)exp{-G(θ)x t }. For appropriate choice ofH andG the marginal distribution ofX t is the (univariate) gamma distribution. In this case, the joint p.d.f. ofX t +1,...,X t+n and its LT, are obtained, and this is extended to a seasonal version of the chain. A simple method of generating observations from these multivariate gamma distributions is noted, and the joint LT is applied to the problem of determining moments of weighted sums of such variables.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 164
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 239-254 
    ISSN: 1436-3259
    Keywords: Water deficit ; Geometric distribution ; Exponential distribution ; Deficit duration ; Deficit severity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract This paper presents an approach to perform statistical frequency analysis of water deficit duration and severity using respectively the geometric and exponential distributions. Monthly mean water discharges are compared to a given threshold and classified in two mutually exclusive ways. This leads to a two state random variable such that: a success represents the absence of a water deficit event (mean monthly discharge exceeds threshold), and a failure, a water deficit event (mean monthly discharge is below threshold). If we suppose that this random variable gives rise to a Markov process of order 1, then the duration of a water deficit event X (consecutive months in deficit) will have a geometric distribution. In turn, the summation of discharges in deficit will give the severity of a water deficit event which can be represented by a one-parameter exponential distribution. The threshold or base level is taken as a percentile of the observed mean discharges of a given month. This base level, which varies from month to month, can be viewed as the limit of an acceptable deficit (or energetic failure) associated to a given empirical probability of being in deficit. The second step of the approach is to estimate the value of the parameter for each distribution using the maximum likelihood method. Expressions for the estimator of a given percentile, $$\hat x_q $$ , as well as its variance are deduced. Finally, the presented models are applied to observed data.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 165
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 7 (1993), S. 1-13 
    ISSN: 1436-3259
    Keywords: Unbiased plotting position ; General Extreme Value distribution ; order statistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Expressions for the expected values of GEV order statistics have been derived in simple summation form and in terms of probability weighted moments. Using exact plotting positions from GEV order statistics a new unbiased plotting position formula has been developed for the General Extreme Value distribution. The formula can, explicitly, take into account the coefficient of skewness, γ (or the shape parameter, k), of the underlying distribution. The developed formula better approximates the exact plotting positions as compared to other existing formulae and is quite easy to use.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 166
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 7 (1993), S. 14-32 
    ISSN: 1436-3259
    Keywords: Stochastic hydrology ; random fields ; space transformation ; perturbation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract This paper develops concepts and methods to study stochastic hydrologic models. Problems regarding the application of the existing stochastic approaches in the study of groundwater flow are acknowledged, and an attempt is made to develop efficient means for their solution. These problems include: the spatial multi-dimensionality of the differential equation models governing transport-type phenomena; physically unrealistic assumptions and approximations and the inadequacy of the ordinary perturbation techniques. Multi-dimensionality creates serious mathematical and technical difficulties in the stochastic analysis of groundwater flow, due to the need for large mesh sizes and the poorly conditioned matrices arising from numerical approximations. An alternative to the purely computational approach is to simplify the complex partial differential equations analytically. This can be achieved efficiently by means of a space transformation approach, which transforms the original multi-dimensional problem to a much simpler unidimensional space. The space transformation method is applied to stochastic partial differential equations whose coefficients are random functions of space and/or time. Such equations constitute an integral part of groundwater flow and solute transport. Ordinary perturbation methods for studying stochastic flow equations are in many cases physically inadequate and may lead to questionable approximations of the actual flow. To address these problems, a perturbation analysis based on Feynman-diagram expansions is proposed in this paper. This approach incorporates important information on spatial variability and fulfills essential physical requirements, both important advantages over ordinary hydrologic perturbation techniques. Moreover, the diagram-expansion approach reduces the original stochastic flow problem to a closed set of equations for the mean and the covariance function.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 167
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 7 (1993), S. 41-65 
    ISSN: 1436-3259
    Keywords: Moment ratio diagrams ; Log-Pearson Type III ; Generalized Gamma ; geometric mean ; harmonic mean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract We refocus attention on moment ratio diagrams and their uses in hydrology with four major objectives: (1) to summarize the information available in the literature about possible uses of the traditional moment ratio diagram introduced by Karl Pearson, which uses the coefficient of skewness and of kurtosis to compare the shapes of various distributions commonly used in hydrology; (2) to complete this traditional MRD by integrating into it the regions occupied by the log-Pearson Type III and generalized gamma distributions which are more and more used in hydrology; (3) to present another MRD which uses ratios of moments of orders −1 (harmonic mean), quasi zero (geometric mean) and 1 (arithmetic mean); (4) to stress the need to consider the different MRD's (along with the more recently introduced L-moment ratio diagrams) as complementary tools for choosing between distributions fitted to hydrologic data. Finally, using Monte Carlo simulation we compare the two types of diagrams as tools to identify and discriminate between different distributions.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 168
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 7 (1993), S. 109-130 
    ISSN: 1436-3259
    Keywords: Particle models ; transport equations ; parameter identification ; adjoint modelling ; cost function ; gradient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract For the simulation of the transport of dissolved matter particle models can be used. In this paper a technique is developed for the identification of uncertain parameters in these models. This model calibration is formulated as an optimization problem and is solved with a gradient based algorithm. Here adjoint particle tracks are used for the calculation of the gradient of the cost function. The performance of the calibration method is illustrated by simulations and an application to a river Rhine water quality calamity in November 1986.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 169
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 7 (1993), S. 146-160 
    ISSN: 1436-3259
    Keywords: EOF analysis ; numerical approximations ; sampling effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Empirical Orthogonal Function (EOF) analysis of spatial random fields involves calculation of the eigenfunctions of the covariance kernel of the field. For real-world applications, a numerical approximation is necessary because the process is spatially discretized. An approximation for two-dimensional fields is proposed and then, analytical solutions of the integral problem are derived and used to study the accuracy of the numerical approximations. Sampling effects are also considered.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 170
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 12 (1998), S. 155-170 
    ISSN: 1436-3259
    Keywords: Keywords: Stochastic inverse model ; conditioning ; transient groundwater flow.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract We investigated the effect of conditioning transient, two-dimensional groundwater flow simulations, where the transmissivity was a spatial random field, on time dependent head data. The random fields, representing perturbations in log transmissivity, were generated using a known covariance function and then conditioned to match head data by iteratively cokriging and solving the flow model numerically. A new approximation to the cross-covariance of log transmissivity perturbations with time dependent head data and head data at different times, that greatly increased the computational efficiency, was introduced. The most noticeable effect of head data on the estimation of head and log transmissivity perturbations occurred from conditioning only on spatially distributed head measurements during steady flow. The additional improvement in the estimation of the log transmissivity and head perturbations obtained by conditioning on time dependent head data was fairly small. On the other hand, conditioning on temporal head data had a significant effect on particle tracks and reduced the lateral spreading around the center of the paths.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 171
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 12 (1998), S. 191-204 
    ISSN: 1436-3259
    Keywords: Keywords: groundwater flow ; inverse problems ; stability ; geostatistical interpolation ; kriging.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The Differential System Method (DSM) permits identification of the physical parameters of finite-difference groundwater flow models in a confined aquifer when piezometric head and source terms are known at each point of the finite-difference lattice for at least two independent flow situations for which the hydraulic gradients are not parallel. Since piezometric head data are usually few and sparse, interpolation of the measured data onto a regular grid can be performed with geostatistical techniques. We apply kriging to the sparse data of a synthetic aquifer to evaluate the stability of the DSM with respect to uncorrelated measurement errors and interpolation errors. The numerical results show that the DSM is stable.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 172
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 12 (1998), S. 171-190 
    ISSN: 1436-3259
    Keywords: Keywords: Self-Calibrated method ; Stochastic hydrology ; Conditional simulation ; Stochastic inversion.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract: A common approach for the performance assessment of radionuclide migration from a nuclear waste repository is by means of Monte-Carlo techniques. Multiple realizations of the parameters controlling radionuclide transport are generated and each one of these realizations is used in a numerical model to provide a transport prediction. The statistical analysis of all transport predictions is then used in performance assessment. In order to reduce the uncertainty on the predictions is necessary to incorporate as much information as possible in the generation of the parameter fields. In this regard, this paper focuses in the impact that conditioning the transmissivity fields to geophysical data and/or piezometric head data has on convective transport predictions in a two-dimensional heterogeneous formation. The Walker Lake data based is used to produce a heterogeneous log-transmissivity field with distinct non-Gaussian characteristics and a secondary variable that represents some geophysical attribute. In addition, the piezometric head field resulting from the steady-state solution of the groundwater flow equation is computed. These three reference fields are sampled to mimic a sampling campaign. Then, a series of Monte-Carlo exercises using different combinations of sampled data shows the relative worth of secondary data with respect to piezometric head data for transport predictions. The analysis shows that secondary data allows to reproduce the main spatial patterns of the reference transmissivity field and improves the mass transport predictions with respect to the case in which only transmissivity data is used. However, a few piezometric head measurements could be equally effective for the characterization of transport predictions.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 173
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 12 (1998), S. 205-222 
    ISSN: 1436-3259
    Keywords: Key words: Hale cycle ; luni-solar tidal constituent ; maximum entropy spectrum ; multi-taper method ; harmonic analysis.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract: Cohen and Sweeter (1975) found the 20 to 22-year Hale (double sunspot) cycle signal in the maximum entropy spectra of sunspot and Atlantic tropical cyclone data. Currie (1996) corroborated and extended their analysis, but he argued that this signal is the 18.6-year luni-solar tidal constituent. Currie maintains that Cohen and Sweeter mistakenly conjectured that this long term periodicity was induced by the 20 to 22-year Hale cycle signal. However, no further investigation of periodicity in the extracted wave forms corresponding to the 18.6-year luni-solar signal was conducted. In this study, we follow Currie's signal processing procedures to extract the wave forms corresponding to the 18.6-year luni-solar signal. In order to investigate the periodicity in the extracted wave forms, multi-taper method (MTM) is used for harmonic analysis. Band pass filters are then designed to extract the wave forms corresponding to the individual components identified in the MTM harmonic analysis. The investigation results of the monthly precipitation and Palmer's drought severity index (PDSI) data in three of the midwestern states – Illinois, Indiana and Ohio – show that two periodic components, the 20 to 22-year Hale cycle signal and the other component with periods between 16.9 and 13.5 years, are identified. The bistability phenomenon, which Currie found in these wave forms, is more likely to result from the superposition of these two periodic components, rather than from a nonlinear mechanism. Besides, a periodic component with an approximate period of 33 years is detected.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 174
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 139-155 
    ISSN: 1436-3259
    Keywords: Porous media ; random media ; random fields ; groundwater flow ; stochastic hydrology ; stochastic partial differential equations ; perturbation methods ; Taylor expansions ; hierarchical systems ; Green's functions ; effective conductivity ; homogenization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract This paper investigates analytical solutions of stochastic Darcy flow in randomly heterogeneous porous media. We focus on infinite series solutions of the steady-state equations in the case of continuous porous media whose saturated log-conductivity (lnK) is a gaussian random field. The standard deviation of lnK is denoted ‘σ’. The solution method is based on a Taylor series expansion in terms of parameter σ, around the value σ=0, of the hydraulic head (H) and gradient (J). The head solution H is expressed, for any spatial dimension, as an infinite hierarchy of Green's function integrals, and the hydraulic gradient J is given by a linear first-order recursion involving a stochastic integral operator. The convergence of the ‘σ-expansion’ solution is not guaranteed a priori. In one dimension, however, we prove convergence by solving explicitly the hierarchical sequence of equations to all orders. An ‘infinite-order stochastic solution is obtained in the form of a σ-power series that converges for any finite value of σ. It is pointed out that other expansion methods based on K rather than lnK yield divergent series. The infinite-order solution depends on the integration method and the boundary conditions imposed on individual order equations. The most flexible and general method is that based on Laplacian Green's functions and boundary integrals. Imposing zero head conditions for all orders greater than one yields meaningful far-field gradient conditions. The whole approach can serve as a basis for treatment of higher-dimensional problems.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 175
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 173-183 
    ISSN: 1436-3259
    Keywords: Probability weighted moment ; scaling in rainfall ; stable distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract We present a statistically robust approach based on probability weighted moments to assess the presence of simple scaling in geophysical processes. The proposed approach is different from current approaches which rely on estimation of high order moments. High order moments of simple scaling processes (distributions) may not have theoretically defined values and consequently, their empirical estimates are highly variable and do not converge with increasing sample size. They are, therefore, not an appropriate tool for inference. On the other hand we show that the probability weighted moments of such processes (distributions) do exist and, hence, their empirical estimates are more robust. These moments, therefore, provide an appropriate tool for inferring the presence of scaling. We illustrate this using simulated Levystable processes and then draw inference on the nature of scaling in fluctuations of a spatial rainfall process.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 176
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 9 (1995), S. 49-75 
    ISSN: 1436-3259
    Keywords: Flood frequency analysis ; index flood estimators ; L-moments ; GEV distribution ; regionalization ; probability weighted moments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Our results illustrate the performance of at-site and regional GEV/PWM flood quantile estimators in regions with different coefficients of variation, degrees of regional heterogeneity, record lengths, and number of sites. Analytic approximations of bias and variance are employed. For realistic GEV distributions and short records, the index-flood quantile estimator performs better than a 2-parameter GEV/PWM quantile estimator with a regional shape parameter, or a 3-parameter at-site GEV/PWM quantile estimator, in both humid and especially in arid regions, as long as the degree of regional heterogeneity is moderate. As regional heterogeneity or record lengths increases, 2-parameter estimators quickly dominate. Flood frequency models that assign probabilities larger than 2% to negative flows are unrealistic; experiments employing such distributions provide questionable results. This appraisal generally demonstrates the value of regionalizing estimators of the shape of a flood distribution, and sometimes the coefficient of variation.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 177
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 9 (1995), S. 105-116 
    ISSN: 1436-3259
    Keywords: Nonlocal ; transport ; dispersion ; heterogeneity ; integro-differential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Analysis from a number of different perspectives has shown diffusion and dispersion in natural porous formations to generally be nonlocal in character, i.e., the mass balance involves integro-partial differential equations. Only in certain asymptotic limits do these laws localize to classical partial differential equations. Compiled within is a resume of nonlocal laws that our group has developed over the last few years for systems with physical, chemical and biological heterogeneity. Analytical tools used to obtain these laws are nonequilibrium and equilibrium statistical mechanics, and first-order spectral-perturbation methods. This paper is an expansion of the material presented at the Waterloo conference held in the memory of Dr. Unny.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 178
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 9 (1995), S. 133-149 
    ISSN: 1436-3259
    Keywords: moment-equations ; state-space ; numerical integration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The generation of the second and higher order moment equations for a set of stochastic differential equations based on Ito's differential lemma is difficult, even for small system of equations. From the knowledge of the statistical properties of the Gaussian white noises associated with the parameters and input coefficients of a set of stochastic differential equations of typeA.Ż+B.Z=C(t), a way to automatically generate the second order moment equations in a computer is presented in this paper. The resulting set of first and second order moment equations is also presented in the same state-space form of the original set of stochastic differential equations through a vectorization of the correlation matrix, which takes advantage of its symmetry. The procedure involved here avoids the inversion of matrixA to apply Ito's differential lemma. Therefore, the presented numerical implementation reduces the computational effort required in the formulation and solution of the moment equations. Moreover, other robust and efficient numerical deterministic integration schemes can be equally applied to the solution of the moment equations.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 179
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 9 (1995), S. 238-238 
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 180
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 9 (1995), S. 269-296 
    ISSN: 1436-3259
    Keywords: Stochastic analysis ; diagrams ; groundwater flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract We present a diagrammatic method for solving stochastic 1-D and 2-D steady-state flow equations in bounded domains. The diagrammatic method results in explicit solutions for the moments of the hydraulic head. This avoids certain numerical constraints encountered in realization-based methods. The diagrammatic technique also allows for the consideration of finite domains or large fluctuations, and is not restricted by distributional assumptions. The results of the method for 1-D and 2-D finite domains are compared with those obtained through a realization-based approach. Mean and variance of head are well reproduced for all log-conductivity variances inputted, including those larger than one. The diagrammatic results also compare favorably to hydraulic head moments derived by standard analytic methods requiring a linearized form of the flow equation.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 181
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 1-26 
    ISSN: 1436-3259
    Keywords: Key words: Spatiotemporal ; stochastic ; mapping ; Bayes ; entropy ; computational approach ; physical knowledge bases ; epistemology.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract This paper is concerned with a computational formulation of the Bayesian maximum entropy (BME) mapping method, which can handle rigorously and efficiently spatiotemporal applications of considerable practical importance. BME is a method of modern geostatistics that can integrate and process physical knowledge that belongs to two major bases: general knowledge (i.e., obtained from general principles and laws, summary statistics and background information), and specificatory knowledge (i.e., obtained through experience with the specific situation). BME allows considerable flexibility regarding the choice of an appropriate spatiotemporal map, offers a complete assessment of the mapping uncertainty and contributes to the scientific understanding of the underlying natural phenomenon. Valuable insight is gained by studying a spatiotemporal data set representing water-level elevations at the Equus Beds aquifer (Kansas). Numerical results show that, as was expected in theory, classical geostatistics analysis is obtained as a special case of the considerably more general BME approach. Moreover, modern geostatistical analysis in terms of BME offers more accurate and informative results in practice, by incorporating various sources of physical knowledge that cannot be processed by the classical methods.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 182
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 27-47 
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Stochastic environmental risk assessment considers the effects of numerous biological, chemical, physical, behavioral and physiological processes that involve elements of uncertainty and variability. A methodology for predicting health risks to individuals from contaminated groundwater is presented that incorporates the elements of uncertainty and variability in geological heterogeneity, physiological exposure parameters, and in cancer potency. An idealized groundwater basin is used to perform a parametric sensitivity study to assess the relative impact of (a) geologic uncertainty, (b) behavioral and physiological variability in human exposure and (c) uncertainty in cancer potency on the prediction of increased cancer risk to individuals in a population exposed to contaminants in household water supplied from groundwater. A two-dimensional distribution (or surface) of human health risk was generated as a result of the simulations. Cuts in this surface (fractiles of variability and percentiles of uncertainty) are then used as a measure of relative importance of various model components on total uncertainty and variability. A case study for perchloroethylene or PCE, shows that uncertainty and variability in hydraulic conductivity play an important role in predicting human health risk that is on the same order of influence as uncertainty of cancer potency.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 183
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 66-84 
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Velocity variability at scales smaller than the size of a solute plume enhances the rate of spreading of the plume around its center of mass. Macroscopically, the rate of spreading can be quantified through macrodispersion coefficients, the determination of which has been the subject of stochastic theories. This work compares the results of a volume-averaging approach with those of the advection dominated large-time small-perturbation theory of Dagan [1982] and Gelhar and Axness [1983]. Consider transport of an ideal tracer in a porous medium with deterministic periodic velocity. Using the Taylor-Aris-Brenner method of moments, it has been previously demonstrated [Kitanidis, 1992] that when the plume spreads over an area much larger than the period, the volume-averaged concentration satisfies the advection-dispersion equation with constant coefficients that can be computed. Here, the volume-averaging analysis is extended to the case of stationary random velocities. Additionally, a perturbation method is applied to obtain explicit solutions for small-fluctuation cases, and the results are compared with those of the stochastic macrodispersion theory. It is shown that the method of moments, which uses spatial averaging, for sufficiently large volumes of averaging yields the same result as the stochastic theory, which is based on ensemble averaging. The result is of theoretical but also practical significance because the volume-averaging approach provides a potentially efficient way to compute macrodispersion coefficients. The method is applied to a simplified representation of the Borden aquifer.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 184
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 85-99 
    ISSN: 1436-3259
    Keywords: Key words: Hydraulic diffusivity ; groundwater ; spectral analysis ; stochastic boundaries.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract: This study uses the cyclical frequency to develop the mathematical relationship between hydraulic diffusivity and spectral density functions calculated from groundwater level variation. Such relationship can be applied to (1) unsteady state, one-dimensional confined aquifer with time-dependent water level on both end boundaries, and (2) linearized unconfined aquifer with or without vertical recharge. The spectral density functions of groundwater fluctuations are largely affected by the spectral density functions obtained from time-dependent end boundaries and their cross-spectral density functions. Hydraulic diffusivity of an aquifer can be solved by type-curve matching technique at a specified frequency band under the conditions of (1) confined aquifer having equal time-dependent boundaries on both ends, (2) unconfined aquifer having equal time-dependent boundaries on both ends with surface recharge, and (3) unconfined aquifer subjected to surface recharge but neglecting the water table fluctuations on both end boundaries.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 185
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 113-130 
    ISSN: 1436-3259
    Keywords: Key words: Climatology ; meso-scale convective systems ; classification ; anisotropy ; intermittency ; ergodicity ; upscaling ; level sets.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract: The meta-Gaussian model is fitted to a set of 258 sahelian rainfields. The hypotheses underlying this model are discussed with a special emphasis on its ergodic properties, the scale of the phenomenon and the scale of observation. Then the ability of this model to reproduce some observed features, in particular upscaling properties, is checked from a distributional point of view. Finally, some simple properties of the thresholds which are linked to the area threshold method are described.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 186
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 100-112 
    ISSN: 1436-3259
    Keywords: Key words: Geostatistic ; Gaussian random functions ; anamorphosis ; intermittency ; discontinuous c.d.f ; valid covariance ; internal consistency.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract: For the purpose of numerically studying sahelian storm rainfields, a family of random functions is described with a characterization of its finite dimensional law. Some problems appearing when fitting its functional parameters are put forward and two solutions to bypass those problems are provided, according to the regularity properties of the marginal cumulative distribution function. An illustration of this method is implemented on a set of sahelian rainfields of event accumulation displaying a strong spatial intermittency.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 187
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 365-379 
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract. Conceptual model selection is a key issue in risk assessment studies. We analyze the effect of a number of conceptual aspects related to solute transport in two-dimensional heterogeneous media. The main issues addressed are non-ergodicity, anisotropy in the correlation structure of the transmissivity field, and dispersion at the local scale. In particular, we study the development of a solute plume when mean flow is oriented at an angle with respect to the principal directions of anisotropy. The study is carried out in a Lagrangian framework using Monte Carlo analysis. Of special interest is the evolution of individual plumes. A number of aspects are analyzed, namely the location of the center of mass for each plume and the different ways to compute the angles that the main axes of the plume develop with respect to the direction of the mean flow. Stochastic theories based upon ergodicity conclude that the plume gets oriented in the mean flow direction. In our non-ergodic simulations, the mean of the offset angles, for each individual plume in each particular realization, is offset from the mean flow direction towards the direction of maximum anisotropy. If, instead, the analysis is performed on the ensemble plume (superposition of all different simulations), it is then found oriented closer to the direction of the mean flow than the average offset angle for the different plumes considered separately. This last result adds an extra word of caution to the use of ensemble averaged values in solute transport studies. Serious implications for risk assessment follow from the conceptual model adopted. First, in any single realization there will a large uncertainty in locating the plume at any given time; second, real dilution would be less than what would be expected if the macrodispersion values obtained for ergodic conditions were applied; third, the volume that is affected by a non-zero concentration is smaller than that predicted from macrodispersion concepts; fourth, the orientation of the plume does not correspond to that of the mean flow; and fifth, accounting for local dispersion helps reducing uncertainty.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 188
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 396-415 
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract. We analyze the movement of a solute cloud in a saturated aquifer, resulting from a point-like instantaneous solute injection. Physical heterogeneities of the medium due to spatial variations of the hydraulic conductivity, as well as the chemical heterogeneities due to variations in the linear adsorption coefficient and the degradation rate, are modeled as spatial stochastic processes with exponential autocorrelation functions. Furthermore, cross-correlations between the chemical properties and the conductivity are taken into account. For large transport times, the movement of the solute cloud is characterized by its center-of-mass velocity, by the macroscopic dispersion constant, and the macroscopic degradation rate. These quantities are evaluated using perturbation theory and two different averaging procedures. The first procedure derives the large-scale properties from the central moments of the concentration distribution in a given aquifer realization, and averages over the ensemble afterwards. The second method which is mathematically less demanding obtains large scale transport coefficients from the central moments of the ensemble-averaged concentration distribution. Under the assumption that both prescriptions lead to the same macro-scale quantities, the second approach is usually preferred in literature. The present paper is an extension of the work of Metzger et al. (1996). We show that the two averaging procedures lead to different results in one-dimensional systems, whereas the difference vanishes for higher dimensions. Taking into account the influence of small scale dispersion, we give explicit results for the macroscopic parameters characterizing the solute plume. We analyze the various contributions to these parameters and show how the physical origin of these contributions can be traced back uniquely to fluctuations in the retardation factor, in the flow field, and in the degradation rate, and to the cross-correlations between these inhomogeneities, respectively.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 189
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 416-435 
    ISSN: 1436-3259
    Keywords: Key words: Sequential linear estimator, successive linear estimator, conditional covariance, interpolation with large data sets.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract. A sequential linear estimator is developed in this study to progressively incorporate new or different spatial data sets into the estimation. It begins with a classical linear estimator (i.e., kriging or cokriging) to estimate means conditioned to a given observed data set. When an additional data set becomes available, the sequential estimator improves the previous estimate by using linearly weighted sums of differences between the new data set and previous estimates at sample locations. Like the classical linear estimator, the weights used in the sequential linear estimator are derived from a system of equations that contains covariances and cross-covariances between sample locations and the location where the estimate is to be made. However, the covariances and cross-covariances are conditioned upon the previous data sets. The sequential estimator is shown to produce the best, unbiased linear estimate, and to provide the same estimates and variances as classic simple kriging or cokriging with the simultaneous use of the entire data set. However, by using data sets sequentially, this new algorithm alleviates numerical difficulties associated with the classical kriging or cokriging techniques when a large amount of data are used. It also provides a new way to incorporate additional information into a previous estimation.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 190
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 255-276 
    ISSN: 1436-3259
    Keywords: Stochastic hydrologic process ; daily discharges ; correlated generation ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A geomorphological study at the confluence of the Danube and the Isar in Bavaria required long series of daily discharges in both rivers. A model that generates simultaneous correlated streamflows in both rivers was developed and tested. The model is a modified shot noise model, first developed by Treiber (1975) for a single river, that was adapted to two rivers. It generates correlated pulses of events that produce flow for each river, and these pulses are then convoluted with a river specific systems function. The model, after being calibrated for the two rivers on the basis of 85 years of records, yields artificial series of discharges, in which the statistical properties of the historical records are reproduced. The performance of the model was tested with 20 generated series each 100 years long.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 191
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 321-321 
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 192
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 5 (1991), S. 17-29 
    ISSN: 1436-3259
    Keywords: Co-kriging ; parameter uncertainty ; Bayesian estimation ; radar rainfall ; gage rainfall
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Procedures for estimating rainfall from radar and raingage observations are constructed in a Bayesian framework. Given that the number of raingage measurements is typically very small, mean and variance of gage rainfall are treated as uncertain parameters. Under the assumption that log gage rainfall and log radar rainfall are jointly multivariate normal, the estimation problem is equivalent to lognormal co-kriging with uncertain mean and variance of the gage rainfall field. The posterior distribution is obtained under the assumption that the prior for the mean and inverse of the variance of log gage rainfall is normal-gamma 2. Estimate and estimation variance do not have closed-form expressions, but can be easily evaluated by numerically integrating two single integrals. To reduce computational burden associated with evaluating sufficient statistics for the likelihood function, an approximate form of parameter updating is given. Also, as a further approximation, the parameters are updated using raingage measurements only, yielding closed-form expressions for estimate and estimation variance in the Gaussian domain. With a reduction in the number of radar rainfall data in constructing covariance matrices, computational requirements for the estimation procedures are not significantly greater than those for simple co-kriging. Given their generality, the estimation procedures constructed in this work are considered to be applicable in various estimation problems involving an undersampled main variable and a densely sampled auxiliary variable.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 193
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 5 (1991), S. 172-172 
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The numerical analysis of stochastic differential equations differs significantly from that of ordinary differential equations due to the peculiarities of stochastic calculus. This book provides an introduction to stochastic calculus and stochastic differential equations, both theory and applications. The main emphasise is placed on the numerical methods needed to solve such equations. It assumes an undergraduate background in mathematical methods typical of engineers and physicists, through many chapters begin with a descriptive summary which may be accessible to others who only require numerical recipes. To help the reader develop an intuitive understanding of the underlying mathematicals and hand-on numerical skills exercises and over 100 PC Exercises (PC-personal computer) are included. The stochastic Taylor expansion provides the key tool for the systematic derivation and investigation of discrete time numerical methods for stochastic differential equations. The book presents many new results on higher order methods for strong sample path approximations and for weak functional approximations, including implicit, predictor-corrector, extrapolation and variance-reduction methods. Besides serving as a basic text on such methods. the book offers the reader ready access to a large number of potential research problems in a field that is just beginning to expand rapidly and is widely applicable.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 194
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 5 (1991), S. 207-226 
    ISSN: 1436-3259
    Keywords: Stochastic groundwater flow ; Neumann expansion ; stochastic partial differential equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A stochastic approach is used for the study of flow through highly heterogeneous aquifers. The mathematical model is represented by a random partial differential equation in which the permeability and the porosity are considered to be random functions of position, defined by the average value, constant standard deviation and autocorrelation function characterized by the integral scale. The Laplace transform of the solution of the random partial differential equation is first written as a solution of a stochastic integral equation. This integral equation is solved using a Neumann series expansion. Conditions of convergence of this series are investigated and compared with the convergence of the perturbation series. For mean square convergence, the Neumann expansion method may converge for a larger range of variability in permeability and porosity than the classic perturbation method. Formal expressions for the average and for the correlation moments of the pressure are obtained. The influence of the variability of the permeability and porosity on pressure is analyzed for radial flow. The solutions presented for the pressure at the well, as function of the permeability coefficient of variation, may be of practical interest for evaluating the efficiency of well stimulation operations, such as hydraulic fracturing or acidizing methods, aimed at increasing the permeability around the well.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 195
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 5 (1991), S. 267-279 
    ISSN: 1436-3259
    Keywords: Drought forecasts ; forecast lead time ; forecast skill ; forecast value ; limits of predictability ; propagation of uncertainty ; hydrometeorologic coupling ; drought management decisions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A systemic framework is presented for organizing knowledge about drought forecasting. It includes these topics: couplings among a descriptive drought model, monitoring system, and forecasting system; propagation of uncertainties; types of forecasts and attributes of performance such as the lead time and skill; sufficient measures of skill and economic value of forecasts; theoretical and operational limits of predictability; and the interface between forecasts and drought management decisions. Reviews of operational forecasts of the seasonal snowmelt runoff volumes and forecasts of the seasonal cyclone frequencies. temperature, and precipitation in the United States illustrate the methodological topics, outline the present limits of drought predictability, and suggest promising research paths. Among them are modeling of forecast uncertainties and their propagation from states of atmospheric circulation to states of a hydrologic regime, and exploring novel forms of the hydro-meteorologic coupling that would extend the lead time and/or increase the skill of long-range drought forecasts.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 196
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 5 (1991), S. 295-322 
    ISSN: 1436-3259
    Keywords: Runoff forecasts ; forecast uncertainty ; forecast skill ; forecast message ; Bayesian processor of forecasts ; sufficiency characteristic ; Bayesian correlation score ; stochastic disaggregation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Forecasts of seasonal snowmelt runoff volume provide indispensable information for rational decision making by water project operators, irrigation district managers, and farmers in the western United States. Bayesian statistical models and communication frames have been researched in order to enhance the forecast information disseminated to the users, and to characterize forecast skill from the decision maker's point of view. Four products are presented: (i) a Bayesian Processor of Forecasts, which provides a statistical filter for calibrating the forecasts, and a procedure for estimating the posterior probability distribution of the seasonal runoff; (ii) the Bayesian Correlation Score, a new measure of forecast skill, which is related monotonically to theex ante economic value of forecasts for decision making; (iii) a statistical predictor of monthly cumulative runoffs within the snowmelt season, conditional on the total seasonal runoff forecast; and (iv) a framing of the forecast message that conveys the uncertainty associated with the forecast estimates to the users. All analyses are illustrated with numerical examples of forecasts for six gauging stations from the period 1971–1988.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 197
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 3-4 
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 198
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 7 (1993), S. 66-82 
    ISSN: 1436-3259
    Keywords: Parameter identification ; multiscale ; transport ; adaptive
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Large scale fluctuations in the conductivity field are regionalized and estimated via a maximum likelihood, adjoint-state methodology. Small-scale fluctuations within each region are estimated adaptively via a Kalman-like stochastic filter. The variance and integral scale within each region are assumed to control the small-scale fluctuations. A Monte Carlo technique is used to examine the distribution of large-scale conductivity estimates.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 199
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 156-156 
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 200
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 43-53 
    ISSN: 1436-3259
    Keywords: Missing data ; Interpolation in hydrology ; Multichannel precipitation time series ; Spectral analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The accuracy of an optimum interpolation technique in filling missing values in multichannel (or multisite) hydrologic series containing time-coincident data gaps is examined. The applied methodology is based on the maximum entropy method (MEM) of spectral estimation or multivariate autoregressive modeling and heavily depends upon the properties of multichannel prediction error filter (PEF). Six precipitation time series spatially located within a hydrologic basin are used and time-coincident artificial gaps are created in all six series. The performance of the technique is assessed by comparing the filled-in series to the observed and by employing spectral analysis. The results reveal the usefulness of the method in multichannel hydrologic analysis.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...