A mixed finite-element, finite-volume, semi-implicit discretisation for atmospheric dynamics: Cartesian geometry

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordTo meet the challenges posed by future generations of massively parallel supercomputers a reformulation of the dynamical core for the Met Office’s weather and climate model is presented. This new dynamical core uses explicit finite-volume type discretisations for the transport of scalar fields coupled with an iterated-implicit, mixed finite-element discretisation for all other terms. The target model aims to maintain the accuracy, stability and mimetic properties of the existing Met Office model independent of the chosen mesh while improving the conservation properties of the model. This paper details that proposed formulation and, as a first step towards complete testing, demonstrates its performance for a number of test cases in (the context of) a Cartesian domain. The new model is shown to produce similar results to both the existing semi-implicit semi-Lagrangian model used at the Met Office and other models in the literature on a range of bubble tests and orographically forced flows in two and three dimensions.Natural Environment Research Council (NERC

A mixed finite-element, finite-volume, semi-implicit discretisation for atmospheric dynamics: Spherical geometry

This is the author accepted manuscriptThe reformulation of the Met Office’s dynamical core for weather and climate prediction previously described by the authors is extended to spherical domains using a cubed- sphere mesh. This paper updates the semi-implicit mixed finite-element formulation to be suitable for spherical do- mains. In particular the finite-volume transport scheme is extended to take account of non-uniform, non-orthogonal meshes and uses an advective-then-flux formulation so that increment from the transport scheme is linear in the diver- gence. The resulting model is then applied to a standard set of dry dynamical core tests and compared to the exist- ing semi-implicit semi-Lagrangian dynamical core currently used in the Met Office’s operational model.Natural Environment Research Council (NERC)Natural Environment Research Council (NERC)Engineering and Physical Sciences Research Council (EPSRC)Engineering and Physical Sciences Research Council (EPSRC

The intrinsic shape of galaxy bulges

The knowledge of the intrinsic three-dimensional (3D) structure of galaxy components provides crucial information about the physical processes driving their formation and evolution. In this paper I discuss the main developments and results in the quest to better understand the 3D shape of galaxy bulges. I start by establishing the basic geometrical description of the problem. Our understanding of the intrinsic shape of elliptical galaxies and galaxy discs is then presented in a historical context, in order to place the role that the 3D structure of bulges play in the broader picture of galaxy evolution. Our current view on the 3D shape of the Milky Way bulge and future prospects in the field are also depicted.Comment: Invited Review to appear in "Galactic Bulges" Editors: Laurikainen E., Peletier R., Gadotti D. Springer Publishing. 24 pages, 7 figure

The natural wood regime in rivers

International audienc

Semi-implicit semi-Lagrangian modelling of the atmosphere: A Met Office perspective

The semi-Lagrangian numerical method, in conjunction with semi-implicit time integration, provides numerical weather prediction models with numerical stability for large time steps, accurate modes of interest, and good representation of hydrostatic and geostrophic balance. Drawing on the legacy of dynamical cores at the Met Office, the use of the semi-implicit semi-Lagrangian method in an operational numerical weather prediction context is surveyed, together with details of the solution approach and associated issues and challenges. The numerical properties and performance of the current operational version of the Met Office's numerical model are then investigated in a simplified setting along with the impact of different modelling choices

A mixed finite-element, finite-volume, semi-implicit discretization for atmospheric dynamics: Cartesian geometry

To meet the challenges posed by future generations of massively parallel supercomputers, a reformulation of the dynamical core for the Met Office's weather and climate model is presented. This new dynamical core uses explicit finite-volume type discretizations for the transport of scalar fields coupled with an iterated-implicit, mixed finite-element discretization for all other terms. The target model aims to maintain the accuracy, stability and mimetic properties of the existing Met Office model independent of the chosen mesh while improving the conservation properties of the model. This paper details that proposed formulation and, as a first step towards complete testing, demonstrates its performance for a number of test cases in (the context of) a Cartesian domain. The new model is shown to produce similar results to both the existing semi-implicit semi-Lagrangian model used at the Met Office and other models in the literature on a range of bubble tests and orographically forced flows in two and three dimensions

Il vocabolario di tre nobilissimi linguaggi italiano, illirico e latino, con l\u2019aggiunta di molt\u2019erbe semplici, raccolto dal Molto Reverendo Signor Don Giovanni Tanzlingher.

Si tratta dell'edizione elettronica di un manoscritto (un vocabolario italiano, croato, latino) risalente alla fine del XVII-inizi XVIII. Il manoscritto consta di 1316 pagine. L'edizione elettronica include anche la fotografia digitale del manoscritto. L'edizione elettronica \ue8 stata curata dal Centro SIGNUM della Scuola Normale Superiore di Pisa

Resilience and fault tolerance in high-performance computing for numerical weather and climate prediction

Progress in numerical weather and climate prediction accuracy greatly depends on the growth of the available computing power. As the number of cores in top computing facilities pushes into the millions, increased average frequency of hardware and software failures forces users to review their algorithms and systems in order to protect simulations from breakdown. This report surveys hardware, application-level and algorithm-level resilience approaches of particular relevance to time-critical numerical weather and climate prediction systems. A selection of applicable existing strategies is analysed, featuring interpolation-restart and compressed checkpointing for the numerical schemes, in-memory checkpointing, user-level failure mitigation and backup-based methods for the systems. Numerical examples showcase the performance of the techniques in addressing faults, with particular emphasis on iterative solvers for linear systems, a staple of atmospheric fluid flow solvers. The potential impact of these strategies is discussed in relation to current development of numerical weather prediction algorithms and systems towards the exascale. Trade-offs between performance, efficiency and effectiveness of resiliency strategies are analysed and some recommendations outlined for future developments

Association of Multiple Sclerosis with PM 2.5 levels. Further evidence from the highly polluted area of Padua Province, Italy

Background: Fifty years of epidemiological survey and intra-regional differences in prevalence suggest that environmental factors may be associated with increased multiple sclerosis (MS) risk in Northern Italy. Based on the findings of a previous study carried out in the highly polluted Padan Plain, we further explored the relationship between PM2.5 levels and MS prevalence by comparing bordering areas characterized by quite different environmental conditions, namely the Municipality of Padua and the special protected zone (SPZ) of the Euganean Hills Regional Park, located 15 km from the City. Methods: Three territories were identified; 1) the SPZ, extending over an area of 15.096 hectares and having a total population of 23,980 inhabitants, 2) the urban area of Padua, with a total population of 210,440 inhabitants and repeatedly recognized by the European Invironmental Agency as one of the most polluted Cities of Europe, 3) the Intermediate Zone (IZ), i.e., the area in between the previous two, including part of the urban territories of eight villages adjacent to the SPZ. Demographic and socio-economical data were obtained from official government sources (www.istat.it and www.regione.veneto.it). All Italian MS patients residing in these three areas on December 31, 2018, were registered. PM2.5 concentrations (annual average 1998\u20132018, \u3bcg/m3) were measured by satellite. The correlation between PM2.5 concentrations and MS prevalence was analysed. Results: MS prevalence was significantly higher in Padua City (265/100.000) compared to both the SPZ of the Euganean Hills Park (160/100,000; p < 0.0001) and the IZ (194.4/100,000). Prevalence strongly associated with the annual average concentration of PM2.5 (r = 0.89 p < 0.00001). Conclusion: In the Province of Padua, one of the most polluted areas of Europe, MS prevalence is strongly associated with PM2.5 exposure. Our findings suggest that air pollutants may be one of the possible environmental risk factors for MS in the Veneto Region of Italy