A finite-volume module for simulating global all-scale atmospheric flows

The paper documents the development of a global nonhydrostatic finite-volume module designed to enhance an established spectral-transform based numerical weather prediction (NWP) model. The module adheres to NWP standards, with formulation of the governing equations based on the classical meteorological latitude-longitude spherical framework. In the horizontal, a bespoke unstructured mesh with finite-volumes built about the reduced Gaussian grid of the existing NWP model circumvents the notorious stiffness in the polar regions of the spherical framework. All dependent variables are co-located, accommodating both spectral-transform and grid-point solutions at the same physical locations. In the vertical, a uniform finite-difference discretisation facilitates the solution of intricate elliptic problems in thin spherical shells, while the pliancy of the physical vertical coordinate is delegated to generalised continuous transformations between computational and physical space. The newly developed module assumes the compressible Euler equations as default, but includes reduced soundproof PDEs as an option. Furthermore, it employs semi-implicit forward-in-time integrators of the governing PDE systems, akin to but more general than those used in the NWP model. The module shares the equal regions parallelisation scheme with the NWP model, with multiple layers of parallelism hybridising MPI tasks and OpenMP threads. The efficacy of the developed nonhydrostatic module is illustrated with benchmarks of idealised global weather

The ESCAPE project : Energy-efficient Scalable Algorithms for Weather Prediction at Exascale

In the simulation of complex multi-scale flows arising in weather and climate modelling, one of the biggest challenges is to satisfy strict service requirements in terms of time to solution and to satisfy budgetary constraints in terms of energy to solution, without compromising the accuracy and stability of the application. These simulations require algorithms that minimise the energy footprint along with the time required to produce a solution, maintain the physically required level of accuracy, are numerically stable, and are resilient in case of hardware failure. The European Centre for Medium-Range Weather Forecasts (ECMWF) led the ESCAPE (Energy-efficient Scalable Algorithms for Weather Prediction at Exascale) project, funded by Horizon 2020 (H2020) under the FET-HPC (Future and Emerging Technologies in High Performance Computing) initiative. The goal of ESCAPE was to develop a sustainable strategy to evolve weather and climate prediction models to next-generation computing technologies. The project partners incorporate the expertise of leading European regional forecasting consortia, university research, experienced high-performance computing centres, and hardware vendors. This paper presents an overview of the ESCAPE strategy: (i) identify domain-specific key algorithmic motifs in weather prediction and climate models (which we term Weather & Climate Dwarfs), (ii) categorise them in terms of computational and communication patterns while (iii) adapting them to different hardware architectures with alternative programming models, (iv) analyse the challenges in optimising, and (v) find alternative algorithms for the same scheme. The participating weather prediction models are the following: IFS (Integrated Forecasting System); ALARO, a combination of AROME (Application de la Recherche a l'Operationnel a Meso-Echelle) and ALADIN (Aire Limitee Adaptation Dynamique Developpement International); and COSMO-EULAG, a combination of COSMO (Consortium for Small-scale Modeling) and EULAG (Eulerian and semi-Lagrangian fluid solver). For many of the weather and climate dwarfs ESCAPE provides prototype implementations on different hardware architectures (mainly Intel Skylake CPUs, NVIDIA GPUs, Intel Xeon Phi, Optalysys optical processor) with different programming models. The spectral transform dwarf represents a detailed example of the co-design cycle of an ESCAPE dwarf. The dwarf concept has proven to be extremely useful for the rapid prototyping of alternative algorithms and their interaction with hardware; e.g. the use of a domain-specific language (DSL). Manual adaptations have led to substantial accelerations of key algorithms in numerical weather prediction (NWP) but are not a general recipe for the performance portability of complex NWP models. Existing DSLs are found to require further evolution but are promising tools for achieving the latter. Measurements of energy and time to solution suggest that a future focus needs to be on exploiting the simultaneous use of all available resources in hybrid CPU-GPU arrangements

The ESCAPE project: Energy-efficient Scalable Algorithms for Weather Prediction at Exascale

Abstract. In the simulation of complex multi-scale flows arising in weather and climate modelling, one of the biggest challenges is to satisfy strict service requirements in terms of time to solution and to satisfy budgetary constraints in terms of energy to solution, without compromising the accuracy and stability of the application. These simulations require algorithms that minimise the energy footprint along with the time required to produce a solution, maintain the physically required level of accuracy, are numerically stable, and are resilient in case of hardware failure. The European Centre for Medium-Range Weather Forecasts (ECMWF) led the ESCAPE (Energy-efficient Scalable Algorithms for Weather Prediction at Exascale) project, funded by Horizon 2020 (H2020) under the FET-HPC (Future and Emerging Technologies in High Performance Computing) initiative. The goal of ESCAPE was to develop a sustainable strategy to evolve weather and climate prediction models to next-generation computing technologies. The project partners incorporate the expertise of leading European regional forecasting consortia, university research, experienced high-performance computing centres, and hardware vendors. This paper presents an overview of the ESCAPE strategy: (i) identify domain-specific key algorithmic motifs in weather prediction and climate models (which we term Weather & Climate Dwarfs), (ii) categorise them in terms of computational and communication patterns while (iii) adapting them to different hardware architectures with alternative programming models, (iv) analyse the challenges in optimising, and (v) find alternative algorithms for the same scheme. The participating weather prediction models are the following: IFS (Integrated Forecasting System); ALARO, a combination of AROME (Application de la Recherche à l'Opérationnel à Meso-Echelle) and ALADIN (Aire Limitée Adaptation Dynamique Développement International); and COSMO–EULAG, a combination of COSMO (Consortium for Small-scale Modeling) and EULAG (Eulerian and semi-Lagrangian fluid solver). For many of the weather and climate dwarfs ESCAPE provides prototype implementations on different hardware architectures (mainly Intel Skylake CPUs, NVIDIA GPUs, Intel Xeon Phi, Optalysys optical processor) with different programming models. The spectral transform dwarf represents a detailed example of the co-design cycle of an ESCAPE dwarf. The dwarf concept has proven to be extremely useful for the rapid prototyping of alternative algorithms and their interaction with hardware; e.g. the use of a domain-specific language (DSL). Manual adaptations have led to substantial accelerations of key algorithms in numerical weather prediction (NWP) but are not a general recipe for the performance portability of complex NWP models. Existing DSLs are found to require further evolution but are promising tools for achieving the latter. Measurements of energy and time to solution suggest that a future focus needs to be on exploiting the simultaneous use of all available resources in hybrid CPU–GPU arrangements

A finite-volume module for simulating global all-scale atmospheric flows

This paper was accepted for publication in the Journal of Computational Physics and the definitive published version is available at http://dx.doi.org/10.1016/j.jcp.2016.03.015.The paper documents the development of a global nonhydrostatic finite-volume module designed to enhance an established spectral-transform based numerical weather prediction (NWP) model. The module adheres to NWP standards, with formulation of the governing equations based on the classical meteorological latitude-longitude spherical framework. In the horizontal, a bespoke unstructured mesh with finite-volumes built about the reduced Gaussian grid of the existing NWP model circumvents the notorious stiffness in the polar regions of the spherical framework. All dependent variables are co-located, accommodating both spectral-transform and grid-point solutions at the same physical locations. In the vertical, a uniform finite-difference discretisation facilitates the solution of intricate elliptic problems in thin spherical shells, while the pliancy of the physical vertical coordinate is delegated to generalised continuous transformations between computational and physical space. The newly developed module assumes the compressible Euler equations as default, but includes reduced soundproof PDEs as an option. Furthermore, it employs semi-implicit forward-in-time integrators of the governing PDE systems, akin to but more general than those used in the NWP model. The module shares the equal regions parallelisation scheme with the NWP model, with multiple layers of parallelism hybridising MPI tasks and OpenMP threads. The efficacy of the developed nonhydrostatic module is illustrated with benchmarks of idealised global weather

Sverigedemokraternasanvändning av begreppet”svenskfientlighet” : en diskursanalys

The Sweden Democrats uses a term to describe a situation where “swedes” are being discriminated against by other ethnic groups and where the elite is promoting this. The term “svenskfientlighet” can be translated as “swedofobia” and in this thesis a speech by the party leader Jimmie Åkesson held during the election campaign that solely was dedicated to this term is being analyzed with the help of tools developed by the scholar Ruth Wodak. Ruth Wodak has previously analyzed the rhetoric by other European right-wing-populist parties like FPÖ in Austria and has asked for other researchers to analyze the speech used by right-wing-populist and extremist parties to get a better understanding for just how these parties construct their different enemies. This thesis show how the Sweden Democrats use a term that has been founded by more extreme parties, groups that they themselves claim they do not have much in common with. The rhetoric has though developed in a populist direction where the party members or even leaders put themselves in a position as victims of a widely spread hostility directed towards them, on the sole basis that they stand up for what is Swedish

Intervjuer mot väggen : en analys av svenska och brittiska radio- och teve-journalisters frågeteknik

Intervjun är en central beståndsdel av journalistiken, både som arbetsmetod och som presentationsform.  Inte minst i ett journalistiskt ansvarsutkrävande i granskningen av politiker och andra makthavare. Trots intervjuns centrala roll, finns det relativt lite forskning runt den journalistiska intervjun. I denna skrift presenteras en studie av sex politiska intervjuer i Sveriges Radio, SVT och brittiska BBC. Dessa intervjuer analyseras ur fyra olika perspektiv – det normativa journalistiska perspektivet, ett samtalsanalytiskt perspektiv, ett retoriskt perspektiv samt ur ett diskursteoretiskt perspektiv

Sverigedemokraternasanvändning av begreppet”svenskfientlighet” : en diskursanalys

The Sweden Democrats uses a term to describe a situation where “swedes” are being discriminated against by other ethnic groups and where the elite is promoting this. The term “svenskfientlighet” can be translated as “swedofobia” and in this thesis a speech by the party leader Jimmie Åkesson held during the election campaign that solely was dedicated to this term is being analyzed with the help of tools developed by the scholar Ruth Wodak. Ruth Wodak has previously analyzed the rhetoric by other European right-wing-populist parties like FPÖ in Austria and has asked for other researchers to analyze the speech used by right-wing-populist and extremist parties to get a better understanding for just how these parties construct their different enemies. This thesis show how the Sweden Democrats use a term that has been founded by more extreme parties, groups that they themselves claim they do not have much in common with. The rhetoric has though developed in a populist direction where the party members or even leaders put themselves in a position as victims of a widely spread hostility directed towards them, on the sole basis that they stand up for what is Swedish

Intervjuer mot väggen : En analys av svenska och brittiska radio- och teve-journalisters frågeteknik

De metoder som används i de studerade svenska intervjuerna (”Lördagsintervjun” och”Sverker rakt på”) för samman reportern och politikern istället för att visa på oberoende. Denfrågeteknik som används skapar intimitet snarare än konfrontation och därför ställs intemakten till svars. Detta görs i uppsatsen tydligt genom en jämförelse med brittiska politiskaintervjuer.I uppsatsen analyseras sex etersända politikerintervjuer från fyra teoretiska perspektiv - detnormativa journalistiska perspektivet, samtalsanalysen, retoriken och maktanalysen. Breddenpå frågorna tydliggör hur de olika intervjuarna ställer sina frågor och hur de fungerar med deolika intervjupersonerna. Slutsatsen är att svenska reportrar ogärna agerar konfrontativt ochhellre vill vara vän med den de intervjuar. Den vänskapliga stämningen leder till att denintervjuade inte ställs till svars, samtidigt fungerar intimiteten utestängande för dem som intesympatiserar. Journalisten och politikern hamnar på samma sida och utestänger den lyssnaresom är journalistens uppdragsgivare.Studien visar också att de svenska journalisterna inte har en teknik som är oberoende av vemde intervjuar. I de brittiska intervjuerna kombineras ett hårt ifrågasättande med en respektfulldistans. I de svenska intervjuerna finns ett behov av lättsamhet som hindrar ifrågasättandet.De sex intervjuerna som studien bygger på är: Jimmie Åkesson i BBC:s Hardtalk, Carl Bildt iBBC:s Hardtalk, Jimmie Åkesson i Sveriges Radios Lördagsintervju, Carl Bildt i SverigesRadios Lördagsintervju, Jimmie Åkesson i SVT:s ”Sverker Rakt på sak” samt Anders Borg i”Sverker Rakt på sak”