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Mesh adaption strategiesfor shallow water flow
Full text linkThe use of unstructured grids for the numerical approximation of partial
differential equations of applied mathematics has the great appeal of enabling mesh adaption based on suitable error indicators of the accuracy of the solution, refining the mesh where the numerical error is large and
coarsening it where the error is small. In this way it is then possible to
optimize the quality of the solution for a given computational effort. We
deal here with mesh adaption applied to shallow water flow. The shallow
water equations are numerically approximated by a standard Galerkin finite
element method, using linear elements for the elevation field and quadratic
elements for the unit-width discharge field. The advancing-in-time scheme
used is of fractional step type. The standard mesh refinement technique is
used; movement and elimination of nodes of the initial triangulation is not
allowed. Two empirical error indicators are proposed and applied here to to
an ideal case of steady flow. The numerical tests show that mesh adaption
is a very reliable tool for numerical simulation of shallow water steady flow.
Any of the used error indicators produce numerical results that are strongly
improved with respect to a uniform mesh, with only a minor increase in the
computational effort
Meteorological forecasting for the European Southern Observatories in Chile
No full textThe potential of numerical weather prediction to supply a useful support to flexible scheduling of astronomical observations is investigated. We applied some common tools presently used in numerical meteorology at regional scale in order to evaluate the ability to forecast local meteorological conditions (cloud cover, air temperature and wind speed) at Cerro Paranal and Cerro La Silla in Chile, where telescopes of ESO (the European Southern Observatory) are sited. The first part of this paper is devoted to evaluating the accuracy of analysis and forecasts of the ECMWF (European Center for Medium-range Weather Forecast) general circulation model for ESO needs. With this aim, analysis and 24-48 hour forecasts from ECMWF are systematically compared with observations at the ground meteorological stations of Paranal and La Silla, and with vertical profiles of radiosounding launches at Antofagasta and Quintero. The second part of this paper is aimed at improving the ECMWF forecasts at telescope sites by means of Kalman filter statistical post-processing and meteorological limited area modeling. Encouraging results are obtained concerning temperature, whereas much less satisfactory results are obtained for wind field and cloud cover. The most critical aspects of atmospheric dynamics affecting the local forecast are discussed within the limits of available information
Planning in marginal areas: local communities network-systems in central-eastern Sardinia
No full textCharacterization of temperature and precipitation fields over Sardinia with Principal Component Analysis and Singular Spectrum Analysis
No full textPlanning in marginal areas: local communities network-systems in Central-Eastern Sardinia
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