163 research outputs found
CONTROL OF COUPLING MASS BALANCE ERROR IN A PROCESS- BASED NUMERICAL MODEL OF SURFACE-SUBSURFACE FLOW INTERACTION
No full textKEY POINTS
• Sources of mass balance error in a process-based hydrological model of surface-subsurface flow interaction are investigated to improve the model’s coupling scheme
• These sources of mass balance error are identified by using a set of dimensionless indices and the analysis of temporal and spatial patterns of error
• A time step control based on a degree of coupling index is proposed and the interpolation algorithm used to pass exchange variables of surface-subsurface flow interaction is improve
Control of mass balance error in a detailed model of surface-subsurface flow interaction
No full textSeveral process-based catchment-scale hydrologic models have been developed in recent years to describe the interactions and feedbacks between different components of the water cycle, but few studies have considered the sources of coupling error in these models. In this work we analyze the sequential iterative coupling scheme of the distributed model CATHY (CATchment HYdrology) in order to identify the different sources of mass balance error and to examine how these are influenced by topography, hydraulic properties, and atmospheric forcing. A pair of adimensional indices that quantify the degree of coupling and of flux partitioning is presented. Our analysis shows that mass balance errors increase during the flood recession limb because of the exchange of information between surface and subsurface water flow. Surface water propagation is cell centered, while the subsurface flow equation is solved on the vertices of surface cells. Evaluation of surface pressure heads and exchange fluxes is critical on this staggered surface-subsurface mesh, especially during transitions from unsaturated to saturated conditions and vice versa. A modified version of the flux exchange algorithm is introduced that considers the effective availability of water on surface cells. The performance of the model is also improved by introducing a heuristic procedure to control and adapt the time step interval. Starting from numerical stability and convergence constraints, this procedure varies the computational interval as a function of the rate of change of surface saturation via the coupling degree index. A final improvement made to the sequential coupling scheme in CATHY is to solve the surface routing equation after rather than before the subsurface module. We find that the modified version improves the water balance by more than 50% in most of the tests considered for a simple v-shaped catchment. The results so far obtained for the synthetic v-catchment indicate the need for a more comprehensive analysis including real catchments
Robust numerical solution of the reservoir routing equation
No full textThe robustness of numerical methods for the solution of the reservoir routing equation is evaluated. The methods considered in this study are: (1) the Laurenson-Pilgrim method, (2) the fourth-order Runge-Kutta method, and (3) the fixed order Cash-Karp method. Method (1) is unable to handle nonmonotonic outflow rating curves. Method (2) is found to fail under critical conditions occurring, especially at the end of inflow recession limbs, when large time steps (greater than 12. min in this application) are used. Method (3) is computationally intensive and it does not solve the limitations of method (2). The limitations of method (2) can be efficiently overcome by reducing the time step in the critical phases of the simulation so as to ensure that water level remains inside the domains of the storage function and the outflow rating curve. The incorporation of a simple backstepping procedure implementing this control into the method (2) yields a robust and accurate reservoir routing method that can be safely used in distributed time-continuous catchment models. © 2013 Elsevier Ltd
Control of coupling mass balance error in a process-based numerical model of surface-subsurface flow interaction
No full text© 2015. American Geophysical Union. All Rights Reserved.A process-based numerical model of integrated surface-subsurface flow is analyzed in order to identify, track, and reduce the mass balance errors affiliated with the model's coupling scheme. The sources of coupling error include a surface-subsurface grid interface that requires node-to-cell and cell-to-node interpolation of exchange fluxes and ponding heads, and a sequential iterative time matching procedure that includes a time lag in these same exchange terms. Based on numerical experiments carried out for two synthetic test cases and for a complex drainage basin in northern Italy, it is shown that the coupling mass balance error increases during the flood recession limb when the rate of change in the fluxes exchanged between the surface and subsurface is highest. A dimensionless index that quantifies the degree of coupling and a saturated area index are introduced to monitor the sensitivity of the model to coupling error. Error reduction is achieved through improvements to the heuristic procedure used to control and adapt the time step interval and to the interpolation algorithm used to pass exchange variables from nodes to cells. The analysis presented illustrates the trade-offs between a flexible description of surface and subsurface flow processes and the numerical errors inherent in sequential iterative coupling with staggered nodal points at the land surface interface, and it reveals mitigation strategies that are applicable to all integrated models sharing this coupling and discretization approach
Anti-neutrinos from the earth: A reference model and its uncertainties
No full textWe predict geoneutrino fluxes in a reference model based on a detailed description of Earth’s
crust and mantle and using the best available information on the abundances of uranium, thorium,
and potassium inside Earth’s layers. We estimate the uncertainties of fluxes corresponding to
the uncertainties of the element abundances. In addition to distance integrated fluxes, we also
provide the differential fluxes as a function of distance from several sites of experimental interest.
Event yields at several locations are estimated and their dependence on the neutrino oscillation
parameters is discussed
ASSESSMENT OF CLIMATE CHANGE IMPACTS IN A BRAZILIAN CATCHMENT USING A DETAILED HYDROLOGICAL MODEL
No full textA distributed physically-based hydrological model named CATHY (CATchment HYdrology) is used to perform a detailed analysis of the response of Toledo River basin (Paranà, Brazil) to climate projections. CATHY couples a subsurface module, described by a three-dimensional Richards equation, with a surface module, led by a one-dimensional diffusion wave equation. Dynamical coupling is achieved by means of a switching in boundary conditions, from a Dirichlet to a Neumann condition and vice versa. Future climate scenarios are determined from historical time series of daily rainfall and temperature in the study area by applying changes compatible with predictions made by the Intergovernmental Panel on Climate Change (IPCC). A twenty-year simulation is run under four future scenarios and the results are compared with those obtained under an unaltered scenario. It is found that the rise or the lowering of water table level is generally not uniform across the basin, being more significant in the uppermost areas. This suggests that measures of adaptation to climate change effects could be practiced by selecting suitable cultures across drainage basins, especially in the areas where the impact of climate change are most significant
La razionalizzazione della profilassi antibiotica in chirurgia nell’Azienda Ospedaliera Umberto I di Ancona
No full text49) L'ECOGRAFIA I.O. NELLA VALUTAZIONE DELLE LESIONI SECONDARIE DEL FEGATO: ESPERIENZA CLINICA
No full textStandardising policy and technology responses in the immediate aftermath of a pandemic: a comparative and conceptual framework
No full textBackground: The initial policy response to the COVID-19 pandemic has differed widely across countries. Such variability in government interventions has made it difficult for policymakers and health research systems to compare what has happened and the effectiveness of interventions across nations. Timely information and analysis are crucial to addressing the lag between the pandemic and government responses to implement targeted interventions to alleviate the impact of the pandemic. Methods: To examine the effect government interventions and technological responses have on epidemiological and economic outcomes, this policy paper proposes a conceptual framework that provides a qualitative taxonomy of government policy directives implemented in the immediate aftermath of a pandemic announcement and before vaccines are implementable. This framework assigns a gradient indicating the intensity and extent of the policy measures and applies the gradient to four countries that share similar institutional features but different COVID-19 experiences: Italy, New Zealand, the United Kingdom and the United States of America. Results: Using the categorisation framework allows qualitative information to be presented, and more specifically the gradient can show the dynamic impact of policy interventions on specific outcomes. We have observed that the policy categorisation described here can be used by decision-makers to examine the impacts of major viral outbreaks such as SARS-CoV-2 on health and economic outcomes over time. The framework allows for a visualisation of the frequency and comparison of dominant policies and provides a conceptual tool to assess how dominant interventions (and innovations) affect different sets of health and non-health related outcomes during the response phase to the pandemic. Conclusions: Policymakers and health researchers should converge toward an optimal set of policy interventions to minimize the costs of the pandemic (i.e., health and economic), and facilitate coordination across governance levels before effective vaccines are produced. The proposed framework provides a useful tool to direct health research system resources and build a policy benchmark for future viral outbreaks where vaccines are not readily available
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