Virtual Event: Annual Seminar 2020

In this talk I will briefly review the development and state-of-the-art of the Integrated Forecasting System (IFS) model as well as steps taken to secure the future efficiency of IFS in view of emerging HPC architectures, and in view of increasing demand for complex coupled data assimilation and simulations of the hydrological and carbon cycle. Exploring the limits of IFS for simulations with...

To meet the challenges posed by future developments of supercomputers the Met Offices’ Unified Model for climate and weather prediction is being redesigned with the aim of achieving improved scalability and portability whilst remaining at least as accurate as the current model. The new model is named LFRic after Lewis Fry Richardson.

The dynamical core of this new model, Gungho, uses...

ECMWF ensemble forecasts include stochastic perturbations, which are designed to represent model uncertainties. Their inclusion significantly increases the skill of the ensemble forecast at all forecast ranges. Currently, the stochastic perturbations used operationally in the IFS represent model uncertainties that are attributed to the parametrisations of atmospheric physics processes. Recent...

Compatible finite element methods have two aspects that make them exciting for use in dynamical cores. The first is that they extend the linear wave propagation of C grid methods (steady geostrophic modes, lack of spurious pressure modes, absence of spurious inertial oscillation modes) to non-affine grids such as the cubed sphere, whilst allowing flexibility to alter pressure/velocity...

In the past significant progress has been made in terms of downscaling our wave forecasts towards our coasts. We present in this talk the work of the last decade in terms of operational downscaling using unstructured grids and implicit numerical schemes on triangular unstructured grids. Special focus will be numerical limiters and the error order of the discretization itself. We will look at...

Numerical solvers should be efficient, robust and scalable. Solving the sea ice momentum equation is recognized to be a difficult problem. This stems from the fact that sea ice rheology, i.e. the relation between applied stresses and the resulting deformations, is very nonlinear and leads to a stiff system of equations. From a physical point of view, this nonlinearity manifests itself by the...

Earth-System models traditionally use double-precision, 64 bit floating-point numbers to perform arithmetic. According to orthodoxy, we must use such a relatively high level of precision in order to minimise the potential impact of rounding errors on the physical fidelity of the model. However, given the inherently imperfect formulation of our models, and the computational benefits of lower...

The GFDL Finite-Volume Cubed-Sphere Dynamical Core, or FV3, is designed to be an accurate, efficient, and adaptable dynamical core useful for a variety of weather and climate applications. In this talk, I discuss how FV3 is designed, implemented, and used. I recapitulate the history of FV3's development from S-J Lin's original finite-volume advection scheme, to the vertically-Lagrangian FV...

During the last two decades global nonydrostatic atmospheric models have been developed that use alternative spherical tilings to latitude-longitude grids. The Model for Prediction Across Scales (MPAS) is one such model, and it uses a spherical centroidal Voronoi tessellation (SCVT) for its horizontal mesh. A C-grid staggering of the prognostic variables is used within MPAS so as to...

In this talk "transport" means advection. A google scholar search for "numerical advection schemes" gives 140,000 results. And those will mostly be in the atmosphere and ocean modelling community because advection is called convection in mathematics and engineering. Why so many? It is probably because none of them work very well. There is a lot that we demand from our advection schemes:
1....

AROME is a Limited Area Model (LAM) designed for mesoscale "Convection Permitting" applications.
It is the result of the coupling between the ALADIN dynamical core and the MésoNH Physics.

As the IFS, the Aladin DynCore is semi-Lagrangian with a spectral semi-implicit solver and hybrid hydrostatic pressure levels (more than 50% of the code of the dynamics is shared with the IFS). The...

Running simulations on high-performance computers faces new challenges due to e.g. the stagnating or even decreasing per-core speed. This poses new restrictions and therefore challenges on solving PDEs within a particular time frame. Here, disruptive mathematical reformulations which e.g. exploit additional degrees of parallelism also in the time dimension gained increasing interest over the...

In this lecture discontinuous Galerkin (DG) methods for numerical weather prediction (NWP) will be described. Both strengths and limitations of such methods applied to atmospheric modeling will be discussed and possible ways to improve their efficiency reviewed.
A particular strategy based on combining a high order DG discretization with p-adaptivity techniques and efficient semi-Lagrangian...