Air quality forecasts on a kilometer-scale grid over complex Spanish terrains

The CALIOPE Air Quality Forecast System (CALIOPE-AQFS) represents the current state of the art in air quality forecasting systems of high-resolution running on high-performance computing platforms. It provides a 48 h forecast of NO2, O3, SO2, PM10, PM2.5, CO, and C6H6at a 4 km horizontal resolution over all of Spain, and at a 1 km horizontal resolution over the most populated areas in Spain with complex terrains (the Barcelona (BCN), Madrid (MAD) and Andalusia (AND) domains). Increased horizontal resolution from 4 to 1 km over the aforementioned domains leads to finer textures and more realistic concentration maps, which is justified by the increase in NO2/O3spatial correlation coefficients from 0.79/0.69 (4 km) to 0.81/0.73 (1 km). High-resolution emissions using the bottom-up HERMESv2.0 model are essential for improving model performance when increasing resolution on an urban scale, but it is still insufficient. Decreasing grid spacing does not reveal the expected improvement in hourly statistics, i.e., decreasing NO2bias by only ~ 2 µg m-3and increasing O3 bias by ~ 1 µg m-3. The grid effect is less pronounced for PM10, because part of its mass consists of secondary aerosols, which are less affected than the locally emitted primary components by a decreasing grid size. The resolution increase has the highest impact over Barcelona, where air flow is controlled mainly by mesoscale phenomena and a lower planetary boundary layer (PBL). Despite the merits and potential uses of the 1-km simulation, the limitations of current model formulations do not allow confirmation of their expected superiority close to highly urbanized areas and large emissions sources. Future work should combine high grid resolutions with techniques that decrease subgrid variability (e.g., stochastic field methods), and also include models that consider urban morphology and thermal parameters.Postprint (published version

Variational multiscale stabilization of finite and spectral elements for dry and moist atmospheric problems

In this thesis the finite and spectral element methods (FEM and SEM, respectively) applied to problems in atmospheric simulations are explored through the common thread of Variational Multiscale Stabilization (VMS). This effort is justified by three main reasons. (i) the recognized need for new solvers that can efficiently execute on massively parallel architectures ¿a spreading framework in most fields of computational physics in which numerical weather prediction (NWP) occupies a prominent position. Element-based methods (e.g. FEM, SEM, discontinuous Galerkin) have important advantages in parallel code development; (ii) the inherent flexibility of these methods with respect to the geometry of the grid makes them a great candidate for dynamically adaptive atmospheric codes; and (iii) the localized diffusion provided by VMS represents an improvement in the accurate solution of multi-physics problems where artificial diffusion may fail. Its application to atmospheric simulations is a novel approach within a field of research that is still open. First, FEM and VMS are described and derived for the solution of stratified low Mach number flows in the context of dry atmospheric dynamics. The validity of the method to simulate stratified flows is assessed using standard two- and three-dimensional benchmarks accepted by NWP practitioners. The problems include thermal and gravity driven simulations. It will be shown that stability is retained in the regimes of interest and a numerical comparison against results from the the literature will be discussed. Second, the ability of VMS to stabilize the FEM solution of advection-dominated problems (i.e. Euler and transport equations) is taken further by the implementation of VMS as a stabilizing tool for high-order spectral elements with advection-diffusion problems. To the author¿s knowledge, this is an original contribution to the literature of high order spectral elements involved with transport in the atmosphere. The problem of monotonicity-preserving high order methods is addressed by combining VMS-stabilized SEM with a discontinuity capturing technique. This is an alternative to classical filters to treat the Gibbs oscillations that characterize high-order schemes. To conclude, a microphysics scheme is implemented within the finite element Euler solver, as a first step toward realistic atmospheric simulations. Kessler microphysics is used to simulate the formation of warm, precipitating clouds. This last part combines the solution of the Euler equations for stratified flows with the solution of a system of transport equations for three classes of water: water vapor, cloud water, and rain. The method is verified using idealized two- and three-dimensional storm simulations.En esta tesis los métodos de elementos finitos y espectrales (FEM - finite element method y SEM- spectral element method, respectivamente), aplicados a los problemas de simulaciones atmosféricas, se exploran a través del método de estabilización conocidocomo Variational Multiscale Stabilization (VMS). Tres razones fundamentales justifican este esfuerzo: (i) la necesidad de tener nuevos métodos de solución de las ecuaciones diferenciales a las derivadas parciales usando máquinas paralelas de gran escala –un entorno en expansión en muchos campos de la mecánica computacional, dentro de la cual la predicción numérica de la dinámica atmosférica (NWP-numerical weather prediction)representa una aplicación importante. Métodos del tipo basado en elementos(por ejemplo, FEM, SEM, Galerkin discontinuo) presentan grandes ventajas en el desarrollo de códigos paralelos; (ii) la flexibilidad intrínseca de tales métodos respecto a lageometría de la malla computacional hace que esos métodos sean los candidatos ideales para códigos atmosféricos con mallas adaptativas; y (iii) la difusión localizada que VMSintroduce representa una mejora en las soluciones de problemas con física compleja en los cuales la difusión artificial clásica no funcionaría. La aplicación de FEM o SEM con VMS a problemas de simulaciones atmosféricas es una estrategia innovadora en un campo de investigación abierto. En primera instancia, FEM y VMS vienen descritos y derivados para la solución de flujos estratificados a bajo número de Mach en el contexto de la dinámica atmosférica. La validez del método para simular flujos estratificados es verificada por medio de test estándar aceptado por la comunidad dentro del campo deNWP. Los test incluyen simulaciones de flujos térmicos con efectos de gravedad. Se demostrará que la estabilidad del método numérico se preserva dentro de los regímenesde interés y se discutirá una comparación numérica de los resultados frente a aquellos hallados en la literatura. En segunda instancia, la capacidad de VMS para estabilizarmétodos FEM en problemas de advección dominante (i.e. ecuaciones de Euler y ecuaciones de transporte) se implementa además en la solución a elementos espectrales de alto orden en problemas de advección-difusión. Hasta donde el autor sabe, esta es una contribución original a la literatura de métodos basados en elementos espectrales en problemas de transporte atmosférico. El problema de monotonicidad con métodos de alto orden es tratado mediante la combinación de SEM+VMS con una técnica de shockcapturing para un mejor tratamiento de las discontinuidades. Esta es una alternativa a los filtros que normalmente se aplican a SEM para eilminar las oscilaciones de Gibbsque caracterizan las soluciones de alto orden. Como último punto, se implementa un esquema de humedad acoplado con el núcleo en elementos finitos; este es un primer paso hacia simulaciones atmosféricas más realistas. La microfísica de Kessler se emplea para simular la formación de nubes y tormentas cálidas (warm clouds: no permite la formación de hielo). Esta última parte combina la solución de las ecuaciones de Eulerpara atmósferas estratificadas con la solución de un sistema de ecuaciones de transporte de tres estados de agua: vapor, nubes y lluvia. La calidad del método es verificadautilizando simulaciones de tormenta en dos y tres dimensiones

Large Eddy Simulation Studies of Island Effects in the Caribbean Trade Wind Region

In dieser Dissertation wird das kompressible, nicht-hydrostatische und dreidimensionale Modell All Scale Atmospheric Model (ASAM) für Grobstruktur- bzw. Large-Eddy-Simulationen (LES) angewendet, um lokale Inseleffekte in der karibischen Passatwindzone zu untersuchen. Da das Modell bis dato noch keine Anwendung im Bereich von LES feuchter atmosphärischer Grenzschichten und heterogener Oberflächen fand, wurden einige Bestandteile zum Modellcode hinzugefügt oder überarbeitet. Ein Hauptaugenmerk liegt dabei auf das Einbeziehen orographischer Strukturen mittels angeschnittener Zellen (engl. cut cells). Sowohl die räumliche und zeitliche Diskretisierung der Modellgleichungen als auch die nötigen physikalischen Parameterisierungen werden in einer umfassenden Modellbeschreibung zusammengefasst. Die Robustheit und Stabilität der Modellformulierung wird durch eine Reihe von Simulationen idealisierter Testfälle bestätigt. Large-Eddy-Simulationen werden für das Gebiet der Karibikinsel Barbados zur Untersuchung von Inseleffekten bezüglich Grenzschichtmodifikation, Wolkenbildung und vertikaler Durchmischung von Aerosolen durchgeführt. Durch das Vorhandensein einer topographisch strukturierten Inseloberfläche in der Mitte des Modellgebietes muss das Modellsetup offene seitliche Randbedingungen beinhalten. Damit das einströmende Windfeld konsistent mit der Dynamik einer turbulenten, marinen Grenzschicht ist, wird eine neue Methode implementiert und angewendet, welche auf Störungen des potentiellen Temperaturfeldes mittels finiter Amplituden basiert. Beobachtungen aus der SALTRACE-Messkampagne werden benutzt, um die Modellläufe anzutreiben. Die Ergebnisse einiger Sensitivitätstests zeigen Probleme der Modellierung im Bereich der \"Terra incognita\" auf. Dabei handelt es sich um die Modellierung auf räumlichen Skalen, welche zwischen denen von LES und wolkenauflösenden Modellen liegen. Außerdem werden Auswirkungen von entweder turbulent oder laminar anströmenden Windfeldern auf die Simulationsergebnisse untersucht. Besonders die Wolkeneigenschaften im Lee von Barbados werden in diesen Simulationen merklich beeinflusst. Ergebnisse einer weiteren Simulation mit einer sehr starken Passatinversion bringt deren Einfluss auf die Dicke und Höhe der simulierten Wolkenschichten zum Vorschein. Die Veränderung von Saharastaubschichten, welche Barbados über weiträumigen Transport über den Atlantik erreichen, wird analysiert. Die Auswirkungen beinhalten sowohl eine Ausdünnung und ein Absinken dieser Schichten als auch turbulenter Transport in Richtung Erdoberfläche. Die genaue Position der beeinflussten Schichten und die Stärke des turbulenten Mischens werden hauptsächlich von der atmosphärischen Schichtung, der Inversionsstärke und Windscherung gesteuert. Vergleiche zwischen den LES-Modellergebnissen und Daten aus Doppler-Windlidarmessungen zeigen gute Übereinstimmungen in der Formierung der konvektiven Strukturen tagsüber und des Vertikalwindfeldes.In this thesis, the fully compressible, three-dimensional, nonhydrostatic atmospheric model called All Scale Atmospheric Model (ASAM) is utilized for large eddy simulations (LES) to investigate local island effects at the Caribbean. Since the model has not been applied to LES for moist boundary layers and heterogeneous surfaces so far, several parts are added to the model code or reworked. A special focus lies on the inclusion of orographical structures via the cut cell method. Spatial and temporal discretization as well as necessary physical parameterizations are summarized in a thorough model description. The robustness of the model formulation is confirmed by a set of idealized test case simulations. Large eddy simulations are performed for the area of the Caribbean island Barbados to investigate island effects on boundary layer modification, cloud generation and vertical mixing of aerosols. Due to the presence of a topographically structured island surface in the domain center, the model setup has to be designed with open lateral boundaries. In order to generate inflow turbulence consistent with the upstream marine boundary layer forcing, the newly developed cell perturbation method based on finite amplitude perturbations is applied. Observations from the SALTRACE field campaign are used to initialize the model runs. Several numerical sensitivity tests are carried out to demonstrate the problems related to \"gray zone modeling\" beyond LES scales or when the turbulent marine boundary layer flow is replaced by laminar winds. Especially cloud properties west of Barbados (downwind) are markedly affected in these simulations. Results of an additional simulation with a strong trade-wind inversion reveal its effect on cloud layer depth and height. The modification of Saharan dust layers reaching Barbados via long-range transport over the North Atlantic is analyzed. Effects of layer thinning, subsidence and turbulent downward transport near the layer bottom become apparent. The position of these layers and strength of downward mixing is found to be mainly controlled atmospheric stability, inversion strength and wind shear. Comparisons of LES model output with wind lidar data show similarities in the formation of the daytime convective plume and the vertical wind structure

A Review of Element-Based Galerkin Methods for Numerical Weather Prediction: Finite Elements, Spectral Elements, and Discontinuous Galerkin

Numerical weather prediction (NWP) is in a period of transition. As resolutions increase, global models are moving towards fully nonhydrostatic dynamical cores, with the local and global models using the same governing equations; therefore we have reached a point where it will be necessary to use a single model for both applications. The new dynamical cores at the heart of these unified models are designed to scale efficiently on clusters with hundreds of thousands or even millions of CPU cores and GPUs. Operational and research NWP codes currently use a wide range of numerical methods: finite differences, spectral transform, finite volumes and, increasingly, finite/spectral elements and discontinuous Galerkin, which constitute element-based Galerkin (EBG) methods.Due to their important role in this transition, will EBGs be the dominant power behind NWP in the next 10 years, or will they just be one of many methods to choose from? One decade after the review of numerical methods for atmospheric modeling by Steppeler et al. (Meteorol Atmos Phys 82:287–301, 2003), this review discusses EBG methods as a viable numerical approach for the next-generation NWP models. One well-known weakness of EBG methods is the generation of unphysical oscillations in advection-dominated flows; special attention is hence devoted to dissipation-based stabilization methods. Since EBGs are geometrically flexible and allow both conforming and non-conforming meshes, as well as grid adaptivity, this review is concluded with a short overview of how mesh generation and dynamic mesh refinement are becoming as important for atmospheric modeling as they have been for engineering applications for many years.The authors would like to thank Prof. Eugenio Oñate (U. Politècnica de Catalunya) for his invitation to submit this review article. They are also thankful to Prof. Dale Durran (U. Washington), Dr. Tommaso Benacchio (Met Office), and Dr. Matias Avila (BSC-CNS) for their comments and corrections, as well as insightful discussion with Sam Watson, Consulting Software Engineer (Exa Corp.) Most of the contribution to this article by the first author stems from his Ph.D. thesis carried out at the Barcelona Supercomputing Center (BSCCNS) and Universitat Politècnica de Catalunya, Spain, supported by a BSC-CNS student grant, by Iberdrola Energías Renovables, and by grant N62909-09-1-4083 of the Office of Naval Research Global. At NPS, SM, AM, MK, and FXG were supported by the Office of Naval Research through program element PE-0602435N, the Air Force Office of Scientific Research through the Computational Mathematics program, and the National Science Foundation (Division of Mathematical Sciences) through program element 121670. The scalability studies of the atmospheric model NUMA that are presented in this paper used resources of the Argonne Leadership Computing Facility, which is a DOE Office of Science User Facility supported under Contract DE-AC02-06CH11357. SM, MK, and AM are grateful to the National Research Council of the National Academies.Peer ReviewedPostprint (author's final draft

Electromagnetic Radiation

The application of electromagnetic radiation in modern life is one of the most developing technologies. In this timely book, the authors comprehensively treat two integrated aspects of electromagnetic radiation, theory and application. It covers a wide scope of practical topics, including medical treatment, telecommunication systems, and radiation effects. The book sections have clear presentation, some state of the art examples, which makes this book an indispensable reference book for electromagnetic radiation applications

Efficient Radar Forward Operator for Operational Data Assimilation within the COSMO-model

Doppler radars provide unique 3D information about precipitating clouds in high spatial and temporal resolutions. However, the observed quantities (reflectivity, Doppler velocity and polarization properties) are not directly comparable to the variables of numerical prediction models. In order to enable radar data assimilation, a comprehensive modular radar forward operator has been developed

On the predictability of exceptional error events in wind power forecasting —an ultra large ensemble approach—

Exceptional error events in wind power forecasting impose a major obstacle to today’s reliable power supply. The predictability of such error events is fundamentally restricted by the underlying weather forecast, resting on limitations of state-of-the-art numerical prediction systems. This work aims to identify such imminent forecast errors applying a probabilistic approach. To this end, the standard sizes of meteorological ensembles are increased from O(10) to an ultra large ensemble size of O(1000) members to accomplish an improved approximation of the probability density function. For this purpose, a novel approach of an ensemble control system named ESIAS-met has been developed on a Petaflop architecture. Further, an increased ensemble size favors the application of nonlinear data assimilation techniques based on the particle filter, while imposing the challenge of growing computational expenses of a resampling step within the particle filter algorithm. ESIAS-met presents a computationally efficient solution to the problem by realizing a parallel execution of the ensemble. Performance measurements demonstrate strong scalability of the system with up to 4096 members. Moreover, the computational expenses of a particle filter resampling step are shown to become independent of the ensemble size. The ESIAS-met system is further applied to investigate the benefit of an increased ensemble size on the predictability of recent exceptional error events. The analysis reveals, that despite the large ensemble size, the forecast error is only represented by single outliers. Higher order moments prove to provide a robust measure of the proper direction of forecast error and assess their likelihood of appearance. It is shown, that at least O(100) ensemble members are needed to resolve the higher order moments sufficiently well. Hence, the results achieved in this work yield important potential for future warning capabilities of exceptional error events

Bridging Scales in 2- and 3-Dimensional Atmospheric Modeling with Adaptive Mesh Refinement

Complex multi-scale atmospheric phenomena, like tropical cyclones, challenge conventional weather and climate models, which use relatively coarse uniform-grid resolutions to cope with computational costs. Adaptive Mesh Refinement (AMR) techniques mitigate these challenges by dynamically and transiently placing high-resolution grids over salient features, thus providing sufficient local resolution while limiting the computational burden. This thesis explores the development of AMR, a technique that has been featured only sporadically in the atmospheric science literature, within a new nonhydrostatic, finite-volume dynamical core and demonstrates AMR's effectiveness in improving model accuracy and ability to resolve multi-scale features. This high-order finite-volume model implements adaptive refinement in both space and time on a cubed-sphere grid using a mapped-multiblock mesh technique developed with the Chombo AMR library. The AMR dynamical core is implemented in a hierarchy of models of increasing complexity, from an idealized 2D shallow water configuration to the nonhydrostatic 3D equation set with subgrid-scale parameterizations schemes. AMR's numerical accuracy, computational efficiency, and ability to track and resolve multifaceted and evolving features are assessed with a variety of existing and new test cases, implemented within each model iteration. Both static and dynamic refinements are analyzed to determine the strengths and weaknesses of AMR in both complex flows with small-scale features and large-scale smooth flows. The different test cases required different AMR criteria, such as vorticity, or minimum pressure based thresholds, in order to achieve the best accuracy for cost. Simulations show that the model's AMR can accurately resolve key local features in both shallow water and 3D test cases without requiring global high-resolution grids, as the adaptive grids are able to track features of interest reliably without inducing noise or visible distortions at the coarse-fine interfaces. Furthermore, the AMR grids keep degradation of the large-scale smooth flows to a minimum. 2D and 3D physics parameterizations are able to function effectively over multiple levels of refinement, though the parameterizations are sensitive to grid resolution. AMR is most effective when refinement is triggered early or when the base uniform resolution can partially resolve the features of interests. Very coarse base resolutions lead to large initial errors that cannot be overcome by AMR. However, the addition of refinement later in the simulation still results in significant improvements, especially in resolving small-scale features. The research showed that flow properties, such as strong gradients or rainbands, can be sensitive to small changes in AMR criteria. These may delay the onset of the refinement or alter the shape of the refined area, which impacts the evolution of the flow. With coarse base resolutions, the tagging criteria must therefore be uniquely tailored to capture the early growth phases of the feature of interest. A promising refinement technique is a combination of some initial refinement and AMR. The initial refinement limits error growth at the base resolution and ensures that the model can resolve the feature of interest. Overall, AMR is shown to be a powerful modeling approach that bridges the resolution gap for extreme weather events.PHDApplied PhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/147504/1/joferg_1.pd