NWP Training Material 2019

Time	Monday	Tuesday	Wednesday	Thursday	Friday
9.15	Introductions Director of Research and Sarah Keeley	The goal of this session is to provide an overview of the use of generalised curvilinear coordinates in atmospheric numerical models. By the end of the session you should be able to: describe some important aspects of the formulation and implementation of the governing equations in generalised coordinates describe various vertical coordinates employed in atmospheric models indicate the use of generalised coordinates to employ moving mesh adaptivity Christian Kühnlein	The success of the spectral transform method in global NWP in comparison to alternative methods has been overwhelming, with many operational forecast centres (including ECMWF) having madethe spectral transform their method of choice. The lecture will introduce the basic elements of the spectral transform, explain why it has been successful and describe recent developments such as the fast Legendre transform. By the end of the session you should be able to: explain what the spectral transform method is, how it is applied, and describe the latest developments at ECMWF. give reasons why it is successful for global NWP and climate. identify potential disadvantages of the method. Andreas Müller	The aim of this set of lectures is to systematically build theoretical foundations for Numerical Weather Prediction at nonhydrostatic resolutions. In the first part of the lecture, we will discuss a suite of all-scale nonhydrostatic PDEs, including the anelastic, the pseudo-incompressible and the fully compressible Euler equations of atmospheric dynamics. First we will introduce the three sets of nonhydrostatic governing equations written in a physically intuitive Cartesian vector form, in abstraction from the model geometry and the coordinate frame adopted. Then, we will combine the three sets into a single set recast in a form of the conservation laws consistent with the problem geometry and the unified solution procedure. In the second part of the lecture, we will build and document the common numerical algorithm for integrating the generalised set of the governing PDEs put forward in the first part of the lecture. Then, we will compare soundproof and compressible solutions and demonstrate the efficacy of this unified numerical framework for two idealised flow problems relevant to weather and climate. By the end of the lectures you should be able to: explain the form, properties and role of alternative systems of nonhydrostatic PDEs for all scale atmospheric dynamics; explain the importance and key aspects of continuous mappings employed in all-scale atmospheric models; explain the difference between the explicit and semi-implicit algorithms for integrating nonhydrostatic PDEs, the importance of consistent numerical approximations, and the fundamental role of transport and elliptic solvers. Piotr Smolarkiewicz	Practical Session: Advection Schemes Willem Deconinck, Christian Kühnlein, Michail Diamantakis
10.45	Using the 30-year history of ECMWF's Integrated Forecasting System (IFS) as an example, thelecture is an introduction to the development and current state-of-the-art of global numerical weather prediction (NWP), as well as to the challenges faced in the future. It is intended to provide an overview and context for the topics covered in more detail during the course. By the end of the session you should be able to: describe the development of global NWP, the current-state-of-the-art, and future challenges identify relevant areas of research in numerical methods for Earth-System Modelling put into context every subsequent lecture and its purpose Nils Wedi	The aim of this set of lectures is to systematically build theoretical foundations for Numerical Weather Prediction at nonhydrostatic resolutions. In the first part of the lecture, we will discuss a suite of all-scale nonhydrostatic PDEs, including the anelastic, the pseudo-incompressible and the fully compressible Euler equations of atmospheric dynamics. First we will introduce the three sets of nonhydrostatic governing equations written in a physically intuitive Cartesian vector form, in abstraction from the model geometry and the coordinate frame adopted. Then, we will combine the three sets into a single set recast in a form of the conservation laws consistent with the problem geometry and the unified solution procedure. In the second part of the lecture, we will build and document the common numerical algorithm for integrating the generalised set of the governing PDEs put forward in the first part of the lecture. Then, we will compare soundproof and compressible solutions and demonstrate the efficacy of this unified numerical framework for two idealised flow problems relevant to weather and climate. By the end of the lectures you should be able to: explain the form, properties and role of alternative systems of nonhydrostatic PDEs for all scale atmospheric dynamics; explain the importance and key aspects of continuous mappings employed in all-scale atmospheric models; explain the difference between the explicit and semi-implicit algorithms for integrating nonhydrostatic PDEs, the importance of consistent numerical approximations, and the fundamental role of transport and elliptic solvers Piotr Smolarkiewicz	Practical Session: Spectral Transform Method Andreas Müller	Practical Session: Elliptic solvers Andreas Müller, Willem Deconinck, Christian Kühnlein	Practical Session: Advection Schemes Willem Deconinck, Christian Kühnlein, Michail Diamantakis
11.55	During this presentation, we will discuss two of the questions faced by numerical weather prediction scientists as forecast models reach horizontal resolutions of 6 to 2 km: Do we need to abandon the primitive equations for a non-hydrostatic system of equations? Do we still need a deep convection parametrisation? and we will show what answers to these questions are given by very high resolution simulations of the IFS. By the end of the presentation, you should be able to: discuss the limits of the hydrostatic approximation for numerical weather prediction explain the dilemma of parametrizing deep convection versus permitting explicit deep convection at resolution in the grey zone of convection Christian Kühnlein	The aim of this set of lectures is to systematically build theoretical foundations for Numerical Weather Prediction at nonhydrostatic resolutions. In the first part of the lecture, we will discuss a suite of all-scale nonhydrostatic PDEs, including the anelastic, the pseudo-incompressible and the fully compressible Euler equations of atmospheric dynamics. First we will introduce the three sets of nonhydrostatic governing equations written in a physically intuitive Cartesian vector form, in abstraction from the model geometry and the coordinate frame adopted. Then, we will combine the three sets into a single set recast in a form of the conservation laws consistent with the problem geometry and the unified solution procedure. In the second part of the lecture, we will build and document the common numerical algorithm for integrating the generalised set of the governing PDEs put forward in the first part of the lecture. Then, we will compare soundproof and compressible solutions and demonstrate the efficacy of this unified numerical framework for two idealised flow problems relevant to weather and climate. By the end of the lectures you should be able to: explain the form, properties and role of alternative systems of nonhydrostatic PDEs for all scale atmospheric dynamics; explain the importance and key aspects of continuous mappings employed in all-scale atmospheric models; explain the difference between the explicit and semi-implicit algorithms for integrating nonhydrostatic PDEs, the importance of consistent numerical approximations, and the fundamental role of transport and elliptic solvers. Piotr Smolarkiewicz	The aim of this session is to describe the numerical technique used in the ECMWF model for integrating the transport equations of the hydrostatic primitive equation set. We will present an overview of the semi-Lagrangian method and how it is combined with semi-implicit time-stepping to provide a stable and accurate formulation for the ECMWF Integrated Forecasting System (IFS). By the end of this session you should be able to: describe the fundamental concepts of semi-Lagrangian advection schemes, their strengths and weaknesses describe semi-implicit time-stepping and its use in IFS explain the important role these two techniques play for the efficiency of the current IFS system explain the impact that future super-computing architectures may have in the applicability of the semi-Lagrangian technique in high resolution non-hydrostatic global NWP systems. Michail Diamantakis	The aim of this session is to understand the main issues and challenges in parallel computing, and how parallel computers are programmed today. By the end of this session you should be able to explain the difference between shared and distributed memory describe the key architectural features of a supercomputer describe the purpose of OpenMP and MPI on today’s supercomputers identify the reasons for the use of accelerator technology Andreas Müller	The aim of this session is to understand how numerical precision can be traded against computational performance in Earth System modelling. It will be discussed how a reduction in numerical precision will influence model quality and how the minimal level of precision that will still allow simulations at high accuracy can be identified. We will give an overview about existing hardware options to adjust numerical precision to the need of the application. By the end of this session you should be able to describe how rounding errors will impact model simulations that show chaotic dynamics describe the connection between numerical precision, computational performance and predictability recall how a trade off between precision and performance can be realised in Earth System modelling today and in the future Peter Düben
14.15	The goal of this session is to provide an overview of the use of generalised curvilinear coordinates in atmospheric numerical models. By the end of the session you should be able to: describe some important aspects of the formulation and implementation of the governing equations in generalised coordinates describe various vertical coordinates employed in atmospheric models indicate the use of generalised coordinates to employ moving mesh adaptivity Christian Kühnlein	The aim of two lectures is to introduce basis of finite volume and continuous finite element discretisations and relate them to corresponding data structures and mesh generation techniques. The main focus will be on unstructured meshes and their application to global and local atmospheric models. Flexibility, communication overheads, memory requirements and user friendliness of such meshes with be contrasted with those of structured meshes. The most commonly used mesh generation techniques will be highlighted, together with mesh manipulation techniques employed in mesh adaption approaches and will be followed by a discussion of alternative geometrical representations of orography. An example of unstructured meshes’ implementation to non-hydrostatic and hydrostatic atmospheric solvers will provide an illustration of their potential and challenges. By the end of the lecture you should be able to: understand applicability, advantages and disadvantages of selected mesh generation techniques for a given type of application. appreciate importance of data structures in relation to atmospheric models and mesh generation. gain awareness of issues related to flexible mesh generation and adaption. Joanna Szmelter	In this lecture we will give you a brief history of ECMWF and present the main areas of NWP research that is currently being carried out in the centre. We then look at current research challenges and present some of the latest developments that will soon become operational. By the end of the lecture you should be able to: List the main research areas at ECMWF and describe the latest model developments. Sarah Keeley and Andy Brown	The aim of this session is to learn about recent developments in discontinuous higher order spatial discretization methods, such as the Discontinuous Galerkin method (DG), and the Spectral Difference method (SD). These methods are of interest because they can be used on unstructured meshes and facilitate optimal parallel efficiency. We will present an overview of higher order grid point methods for discretizing partial differential equations (PDE's) with compact stencil support, and illustrate a practical implementation. By the end of the session you should be able to: ell what are the advantages offered by discontinuous higher order methods describe how to solve PDE's with discontinuous methods identify the key elements that contribute to a PDE solver Willem Deconinck	Course wrap up and Certificates
15.45	Computer Hall Tour Poster session followed by ice breaker	The aim of two lectures is to introduce basis of finite volume and continuous finite element discretisations and relate them to corresponding data structures and mesh generation techniques. The main focus will be on unstructured meshes and their application to global and local atmospheric models. Flexibility, communication overheads, memory requirements and user friendliness of such meshes with be contrasted with those of structured meshes. The most commonly used mesh generation techniques will be highlighted, together with mesh manipulation techniques employed in mesh adaption approaches and will be followed by a discussion of alternative geometrical representations of orography. An example of unstructured meshes’ implementation to non-hydrostatic and hydrostatic atmospheric solvers will provide an illustration of their potential and challenges. By the end of the lecture you should be able to: understand applicability, advantages and disadvantages of selected mesh generation techniques for a given type of application. appreciate importance of data structures in relation to atmospheric models and mesh generation. gain awareness of issues related to flexible mesh generation and adaption. Joanna Szmelter	The aim of this session is to describe Eulerian based numerical techniques for integrating the equation sets encountered in NWP models. We will present an overview of different time-stepping techniques and discuss the advantages and disadvantages of each approach. By the end of the session you should be able to: obtain a good understanding of the minimum theoretical properties required by time-stepping schemes describe differences, strengths-weaknesses of different time-stepping approaches such as split-explicit time-stepping, Runge-Kutta time-stepping describe the basic features of different time-stepping schemes used in other weather forecasting models such as WRF, ICON Michail Diamantakis	The aim of this session is to learn about recent developments in discontinuous higher order spatial discretization methods, such as the Discontinuous Galerkin method (DG), and the Spectral Difference method (SD). These methods are of interest because they can be used on unstructured meshes and facilitate optimal parallel efficiency. We will present an overview of higher order grid point methods for discretizing partial differential equations (PDE's) with compact stencil support, and illustrate a practical implementation. By the end of the session you should be able to: ell what are the advantages offered by discontinuous higher order methods describe how to solve PDE's with discontinuous methods identify the key elements that contribute to a PDE solver Willem Deconinck

Time	Monday	Tuesday	Wednesday	Thursday	Friday
9:30 -10:45	Meet the course participants	The infrared spectrum- measurement, modelling and information content Tony McNally	GPS Radio Occulation: Extended applications Sean Healy	Satellites for environmental monitoring and forecasting Antje Inness	Satellite information on the ocean surface (SCAT) Giovanna De Chiara
11:15...12:30	Theoretical background (1) What do satellites measure ? Tony McNally	GPS Radio Occulation: Principles and NWP use Sean Healy	The detection and assimilation of clouds in infrared radiances Tony McNally	Background errors for satellite data assimilation Tony McNally	Bias correction methods for satellite data Niels Bormann
14:00...15:15	Theoretical background (2) Data assimilation algorithms, Key elements and inputs Tony McNally	Satellite information on the land surface Patricia de Rosnay	The detection and assimilation of clouds and rain in microwave radiances Alan Geer	Observation errors for satellite data assimilation Niels Bormann	Current satellite observing network and its future evolution Stephen English
15:45...17:00	The microwave spectrum, measurement, modelling and information content Alan Geer	A Practical guide to IR and MW radiative transfer – using the RTTOV model and GUI David Rundle (UK Met Office)	Wind information from satellites (Atmospheric Motion Vectors) Katie Lean	1DVar theory, simulator + practical session on background and observation errors Tony McNally	Question and answer session, course evaluation

After this lecture, students will be able to:

explain the physical and practical motivations for using stochastic physics in an ensemble forecast;
describe the two stochastic parameterization schemes used in the IFS ensemble, and their respective purposes;
be able to identify the improvement in forecasting skill from the inclusion of stochastic physics.

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