Nils Wedi

Nils Wedi
European Center For Medium Range Weather Forecasts · Research Department

PhD

About

101
Publications
25,598
Reads
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3,620
Citations
Additional affiliations
January 2001 - January 2005
Ludwig-Maximilians-University of Munich
Position
  • PhD
Description
  • co-supervisor: Dr Smolarkiewicz
January 1995 - present
European Center For Medium Range Weather Forecasts
Position
  • Analyst/Scientist
January 1990 - January 1995
Johannes Gutenberg-Universität Mainz
Position
  • Student

Publications

Publications (101)
Article
The paper examines horizontal wind variance (kinetic energy spectra) and available potential energy spectra in simulations conducted with a state-of-the-art global numerical weather prediction (NWP) model: the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts. The formulation of the spectral energy budget...
Technical Report
Full-text available
With the objective to develop and maintain one of the most advanced and flexible modelling infrastructures in Europe for operational, global NWP applications, recent advances and future challenges are described. A particular challenge arises from the need to achieve computationally and energy efficient solutions for operating global, complex, high-...
Article
Full-text available
ECMWF hosts the European Research Council-funded project PantaRhei, which explores novel numerical methods to complement existing, highly optimised numerical weather prediction (NWP) models. The need for such innovation stems from the fact that state-of-the-art global NWP models using the spectral transform method may become computationally ineffic...
Article
Full-text available
The steady path of doubling the global horizontal resolution approximately every 8 years in numerical weather prediction (NWP) at the European Centre for Medium Range Forecasts (ECMWF) may be substantially altered with emerging novel computing architectures. It coincides with the need to appropriately address and determine forecast uncertainty with...
Article
With the emergence of non-hydrostatic global dynamical cores, an alternative testing strategy is proposed, where the planetary radius is suitably reduced to capture non-hydrostatic phenomena without incurring the computational cost of actual simulations of weather and climate at non-hydrostatic resolution. The procedure is simple and tests various...
Article
We have implemented a new stratospheric ozone model in the European Centre for Medium-Range Weather Forecasts (ECMWF) system and tested its performance for different timescales to assess the impact of stratospheric ozone on meteorological fields. We have used the new ozone model to provide prognostic ozone in medium-range and long-range (seasonal)...
Article
Full-text available
Convectively generated gravity waves (CGGWs) are important for numerical weather prediction due to their effect on the quasi‐biennial oscillation (QBO) in the stratosphere. Using global ECMWF IFS simulations at TCo7999 (or 1.25km), TCo2559 (or 3.9km) and TCo1279 (or 7.8km) horizontal resolutions, sensitivity of resolved CGGWs to the horizontal reso...
Article
Full-text available
Reducing the numerical precision of the forecast model of the Integrated Forecasting System (IFS) of the European Centre for Medium‐Range Weather Forecasts (ECMWF) from double to single precision results in significant computational savings without negatively affecting forecast accuracy. The computational savings allow to increase the vertical reso...
Article
Full-text available
The increase in computing power and recent model developments allow for the use of global kilometer-scale weather and climate models for routine forecasts. At these scales, deep convective processes can be partially resolved explicitly by the model dynamics. Next to horizontal resolution, other aspects such as the applied numerical methods, the use...
Article
Full-text available
The land-surface developments of the European Centre for Medium-range Weather Forecasts (ECMWF) are based on the Carbon-Hydrology Tiled Scheme for Surface Exchanges over Land (CHTESSEL) and form an integral part of the Integrated Forecasting System (IFS), supporting a wide range of global weather, climate and environmental applications. In order to...
Preprint
The land-surface developments of the European Centre for Medium-range Weather Forecasts (ECMWF) are based on the Carbon-Hydrology Tiled Scheme for Surface Exchanges over Land (CHTESSEL) and form an integral part of the Integrated Forecasting System (IFS), supporting a wide range of global weather, climate and environmental applications. In order to...
Article
Full-text available
The sensitivities of the Madden–Julian oscillation (MJO) forecasts to various different configurations of the parameterized physics are examined with the global model of ECMWF's Integrated Forecasting System (IFS). The motivation for the study was to simulate the MJO as a nonlinear free wave under active interactions with higher-latitude Rossby wav...
Preprint
Full-text available
The increase in computing power and recent model developments allow the use of global kilometer-scale weather and climate models for routine forecasts. At these scales, deep convective processes can be partially resolved explicitly by the model dynamics. Next to horizontal resolution, other aspects such as the applied numerical methods, the use of...
Article
Computational science is crucial for delivering reliable weather and climate predictions. However, despite decades of high-performance computing experience, there is serious concern about the sustainability of this application in the post-Moore/Dennard era. Here, we discuss the present limitations in the field and propose the design of a novel infr...
Article
Full-text available
Recent progress in computing and model development has initiated the era of global storm-resolving modeling and with it the potential to transform weather and climate prediction. Within the general theme of vetting this new class of models, the present study evaluates nine global-storm resolving models in their ability to simulate tropical cyclones...
Preprint
Full-text available
We have implemented a new stratospheric ozone model in the European Centre for Medium-Range Weather Forecasts (ECMWF) system, and tested its performance for different timescales, to assess the impact of stratospheric ozone on meteorological fields. We have used the new ozone model to provide prognostic ozone in medium-range and long-range experimen...
Article
Full-text available
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 f...
Article
Full-text available
Abstract In an attempt to advance the understanding of the Earth's weather and climate by representing deep convection explicitly, we present a global, four‐month simulation (November 2018 to February 2019) with ECMWF's hydrostatic Integrated Forecasting System (IFS) at an average grid spacing of 1.4 km. The impact of explicitly simulating deep con...
Research
Full-text available
Numerical weather and climate prediction rates as one of the scientific appli- cations whose accuracy improvements greatly depend on the growth of the available computing power. As the number of cores in top computing facil- ities pushes into the millions, increasing average frequency of hardware and software failures forces users to review their a...
Article
Full-text available
Global simulations with 1.45 km grid-spacing are presented that were performed with the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). Simulations are uncoupled (without ocean, sea-ice or wave model), using 62 or 137 vertical levels and the full complexity of weather forecast simulations inclu...
Technical Report
The efficiency of the forecasting system on future high-performance computing and data handling systems is considered one of the key challenges for implementing ECMWF’s ambitious strategy. This was already recognised by ECMWF in 2013, and has led to the foundation of the Scalability Programme. The programme aims to address this challenge as a conce...
Preprint
Full-text available
Abstract. Sensitivities of MJO forecasts to various different configurations of physics are examined with the ECMWF global model, IFS. A motivation behind this study is to explore a possibility of interpreting the MJO as a nonlinear free wave under active interactions with Rossby waves from and to higher latitudes. With this motivation in mind, var...
Article
Sensitivities of MJO forecasts to various different configurations of physics are examined with the ECMWF global model, IFS. A motivation behind this study is to explore a possibility of interpreting the MJO as a nonlinear free wave under active interactions with Rossby waves from and to higher latitudes. With this motivation in mind, various momen...
Article
Full-text available
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 requi...
Article
Full-text available
Water bodies influence local weather and climate, especially in lake-rich areas. The FLake (Fresh-water Lake model) parameterisation is employed in the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF) model which is used operationally to produce global weather predictions. Lake depth and lake fra...
Article
Full-text available
A review of the experimental protocol and motivation for DYAMOND, the first intercomparison project of global storm-resolving models, is presented. Nine models submitted simulation output for a 40-day (1 August–10 September 2016) intercomparison period. Eight of these employed a tiling of the sphere that was uniformly less than 5 km. By resolving t...
Article
This paper evaluates the prospects for increasing the horizontal resolution of the Aeolus horizontal line‐of‐sight (HLOS) wind profiles at the expense of their accuracy. The evaluation is performed by combining a 10‐day atmosphere simulation by the ECMWF model at T3999 horizontal resolution with the CALIPSO observations of atmospheric composition a...
Article
This paper derives unified equations of A. Arakawa and C.S. Konor (2009) rigorously formulated in a suitable mass‐based sigma‐coordinate and develops an efficient semi‐implicit integration scheme. The unified equations accurately capture the non‐hydrostatic small‐scale effects and retain the hydrostatic compressibility of the flow at large scales....
Article
Full-text available
The continuous partial differential equations (PDEs) governing a given physical phenomenon, such as the Navier-Stokes equations describing the fluid motion, must be numerically discretised in space and time in order to obtain a solution otherwise not readily available in closed (i.e., analytic) form. While the overall numerical discretization plays...
Article
Full-text available
We apply spectral empirical orthogonal function (SEOF) analysis to educe climate patterns as dominant spatiotemporal modes of variability from reanalysis data. SEOF is a frequency-domain variant of standard empirical orthogonal function (EOF) analysis, and computes modes that represent the statistically most relevant and persistent patterns from an...
Article
Full-text available
Water bodies influence local weather and climate, especially in lake-rich areas (e.g. lake regions in Canada and northern Russia). In 2015 a parametrization to represent inland water bodies was included in the Integrated Forecasting System (IFS) used operationally at the European Centre for Medium-Range Weather Forecasts (ECMWF) to produce global w...
Article
Full-text available
We discuss scientific features and computational performance of kilometre-scale global weather and climate simulations, considering the Icosahedral Non-hydrostatic (ICON) model and the Integrated Forecast System (IFS). Scalability measurements and a performance modelling approach are used to derive performance estimates for these models on upcoming...
Article
Full-text available
We present a nonhydrostatic finite-volume global atmospheric model formulation for numerical weather prediction with the Integrated Forecasting System (IFS) at ECMWF and compare it to the established operational spectral-transform formulation. The novel Finite-Volume Module of the IFS (henceforth IFS-FVM) integrates the fully compressible equations...
Article
Full-text available
In the simulation of complex multi-scale flow problems, such as those arising in weather and climate modelling, one of the biggest challenges is to satisfy operational requirements in terms of time-to-solution and energy-to-solution yet without compromising the accuracy and stability of the calculation. These competing factors require the developme...
Article
We present a roadmap towards exascale computing based on true application performance goals. It is based on two state-of-the art European numerical weather prediction models (IFS from ECMWF and COSMO from MeteoSwiss) and their current performance when run at very high spatial resolution on present-day supercomputers. We conclude that these models e...
Article
Full-text available
In this paper, we review the use of satellite-based remote sensing in combination with in situ data to inform Earth surface modelling. This involves verification and optimization methods that can handle both random and systematic errors and result in effective model improvement for both surface monitoring and prediction applications. The reasons fo...
Article
Full-text available
We present a nonhydrostatic finite-volume global atmospheric model formulation for numerical weather prediction with the Integrated Forecasting System (IFS) at ECMWF, and compare it to the established operational spectral-transform formulation. The novel Finite-Volume Module of IFS (henceforth IFS-FVM) integrates the fully compressible equations us...
Article
Numerical models of the climate system have typically been restricted to grid resolutions from a few hundred down to a few tens of kilometers due to computational constraints, and a representation of sub-grid physical processes by parameterization is required. The continuing advances of science and technology are allowing larger computations and th...
Article
Full-text available
This paper presents a generalised perturbation form of the nonhydrostatic partial differential equations (PDEs) that govern dynamics of all-scale global atmospheric flows. There can be many alternative perturbation forms for any given system of the governing PDEs, depending on the assumed ambient state about which perturbations are taken and on sub...
Article
The 2nd World Climate Research Programme (WCRP) Summer School on Climate Model Development was held in Cachoeira Paulista, São Paulo, Brazil, from January 22nd to January 31st, hosted by the National Institute for Space Research, Center for Weather Forecasting and Climate Studies (INPE/CPTEC) to bring together expert scientists to share knowledge w...
Article
Full-text available
Weather and climate models are complex pieces of software which include many individual components, each of which is evolving under pressure to exploit advances in computing to enhance some combination of a range of possible improvements (higher spatio-temporal resolution, increased fidelity in terms of resolved processes, more quantification of un...
Article
Full-text available
The fifth Workshop on Systematic Errors (WSE) in weather and climate models was hosted by Environment and Climate Change Canada (ECCC) on under the auspices of the Working Group on Numerical Experimentation (WGNE), jointly sponsored by the Commission of Atmospheric Sciences of the World Meteorological Organization (WMO) and the World Climate Resear...
Article
Middle atmospheric lidar temperature observations conducted above Sodankylä, Finland (67.4N, 26.6E), during December 2015 are compared to two estimates of the atmospheric state computed by the integrated forecast system (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). The first set corresponds to an hourly sampling of the mi...
Article
Full-text available
Weather and climate models are complex pieces of software which include many individual components, each of which is evolving under the pressure to exploit advances in computing to enhance some combination of a range of possible improvements (higher spatio/temporal resolution, increased fidelity in terms of resolved processes, more quantification o...
Article
Full-text available
The algorithms underlying numerical weather prediction (NWP) and climate models that have been developed in the past few decades face an increasing challenge caused by the paradigm shift imposed by hardware vendors towards more energy-efficient devices. In order to provide a sustainable path to exascale High Performance Computing (HPC), application...
Article
Full-text available
Members in ensemble forecasts differ due to the representations of initial uncertainties and model uncertainties. The inclusion of stochastic schemes to represent model uncertainties has improved the probabilistic skill of the ECMWF ensemble by increasing reliability and reducing the error of the ensemble mean. Recent progress, challenges and futur...
Article
Full-text available
ESCAPE stands for Energy-efficient Scalable Algorithms for Weather Prediction at Exascale. The project will develop world-class, extreme-scale computing capabilities for European operational numerical weather prediction (NWP) and future climate models. The biggest challenge for state-of-the-art NWP arises from the need to simulate complex physical...
Technical Report
Full-text available
Programme and Abstracts of the 1st ESCAPE Dissemination and Training Workshop on "Towards Energy-efficient Scalable Algorithms for Weather- and Climate Prediction: Status and Prospects", 21 p., 18-20 Oct 2016, Elsinore, Denmark The workshop sessions will be organized according to the following topics (with oral presentations, including keynote spea...
Presentation
Full-text available
The Draupner freak wave: a fresh look and the emerging view
Article
Full-text available
Using the new high-resolution operational model of ECMWF, we revisit the storm during which the Draupner freak wave of January 1, 1995 was recorded. The modeling system gives a realistic evolution of the storm highlighting the crucial role played by the southward propagating polar low in creating the extreme wave conditions present at the time the...
Article
Full-text available
On 1 January 1995 at 15 UTC, the most famous freak wave to be detected by a measuring instrument was recorded by a downward-looking laser at the North Sea Draupner gas platform. The wave was 25.6 m high, with an 18.5 m crest height (Box A). The significant wave height in the area is estimated to have been almost 12 m. The measurement confirmed the...
Chapter
Numerical Weather Prediction (NWP) and climate simulations have been intimately connected with progress in supercomputing since the first numerical forecast was made about 65 years ago. The biggest challenge to state-of-the-art computational NWP arises today from its own software productivity shortfall. The application software at the heart of most...
Article
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 th...
Article
ECMWF hosts the European Research Council-funded project PantaRhei, which explores novel numerical methods to complement existing, highly optimised numerical weather prediction (NWP) models. The need for such innovation stems from the fact that state-of-the-art global NWP models using the spectral transform method may become computationally ineffic...
Research
Full-text available
ECMWF Proceedings Article "Seminar on Recent Developments in Numerical Methods for Atmosphere and Ocean Modelling"
Article
Soil temperature is an important variable for the representation of many physical processes in Numerical Weather Prediction (NWP). It is the key driver for all surface emissions of energy, carbon dioxide, water and forward operator for all satellite sensors sensitive to land. Yet the forecast quality of this variable in NWP is largely unknown. In t...
Chapter
This chapter considers two conspicuous phenomena that are specific to the equatorial zone of rotating planets, where the quasi-horizontal “balance” model obtained from geostrophic theory does not generally apply. In the chapter the direct numerical simulation (DNS) of the laboratory analogue of the quasi-biennial oscillation (QBO) and the large-edd...
Technical Report
Full-text available
An improved description of the Earth surfaces, with particular focus on soil, vegetation, snow and inland water-bodies, has been driving recent research efforts within the ECMWF Integrated Forecasting System (IFS). These developments are considered together with their associated data assimilation components and the representation of inherent uncert...