Cerfacs Enter the world of high performance ...

DDM- Data Assimilation and Optimisation

Data assimilation deals with the problem of estimating model parameters or model state variables by combining prior estimates and observations, together with information about their uncertainties, in a statistically optimal manner. CERFACS has well-established data assimilation activities in oceanography, atmospheric chemistry, hydrology/hydraulics and wildfires, which are conducted in close collaboration with CERFACS partners, and leading operational centres and research institutes in forecasting and retrospective analysis.

Optimization concerns the development of numerical algorithms for solving diverse linear and nonlinear problems. It involves studying the properties of the algorithms, such as convergence and complexity, as well as improving their performance through preconditioning techniques. CERFACS develops derivative-based and derivative-free algorithms for a variety of applications including data assimilation, Earth imaging and aerodynamics design.

Accuracy, efficiency, scalability, robustness and practicability are important considerations when designing methods for data assimilation and optimization. To develop effective methods requires a good understanding of the underlying application and problem characteristics.

The current actions in Data Assimilation at CERFACS are organized in actions :

  • Develop advanced algorithms for variational and ensemble-variational DA
  • Develop advanced methods for modelling and estimating error covariances
  • Develop ensemble generation and surrogate model methodologies for DA
  • Improve and extend the use of in situ and remotely-sensed data in DA

These actions are implemented on Use Cases

  • Use Case #1: Extending methodologies in variational and ensemble-variational DA: Accounting for nonlinearity; model error estimation & representation; preconditioning; developing robust minimization for extreme-valued observations. Implementation & evaluation in OOPS-based and other systems.
  • Use Case #2: Development of flexible and efficient covariance models for B: multi-variate; accounting for rotational anisotropy in correlations; multi-scale; ensembles; localization; SPDEs; preconditioning; hybrid; coupled; estimation procedures; MLMC. Implementation & evaluation in OOPS-based systems including NEMOVAR for ocean DA, and other systems.
  • Use Case #3: Development of flexible and efficient covariance models for R: unstructured meshes; SPDEs; FEMs; 2D, 3D and 4D (space + inter-channel + time); R-1; preconditioning; estimation procedures. Implementation & evaluation in existing Matlab framework and OOPS-based systems.
  • Use Case #4: Development of efficient ensemble-based DA: Ensemble generation & validation methodologies; surrogate models for stochastic covariance estimation. Development for hydraulics, wildfire & pollutant dispersion.
  • Use Case #5: Assimilation of satellite and image data: high-resolution altimeter (SWOT) and SST; high-resolution & hyper-spectral sounders (IASI); patterns/fronts. Developments for hydraulics & hydrology, ocean, atmospheric chemistry, history matching and wildfire applications.

NEWS

CMIP6 debriefing workshop – May 2021: a stocktaking and foresight exercise that highlighted the major and long-term investment of the CNRM-CERFACS group in the latest climate model intercomparison international exercise

CERFACS |  9 June 2021

The participation of the CNRM-CERFACS group in the international coupled global climate model intercomparison exercise CMIP6 was debriefed on 10 and 11 May. Since the mid-1990s, the various phases of the Coupled Model Intercomparison Project (CMIP), supported by the World Climate Research Programme (WCRP), have enabled climate science to make significant progress, feeding into the IPCC reports, supporting regional climate modelling activities and downstream climate services. On the balance sheet, the participation of CNRM-CERFACS in the extremely demanding CMIP6 exercise has resulted in a large-scale, high-quality contribution in terms of climate simulations, thanks in particular to the strong commitment of researchers and engineers, the quality of support services and national and international collaborations. The activities mainly took place over the period 2013-2020. Initially, the production environment ("workflow") was set up and the coupled climate models were assembled by capitalising on the development of components (atmosphere, ocean and continental surfaces) carried out over the long term. The actual production of simulations was spread over 2018-2020. During the debriefing, perspectives (scientific objectives, model development, organisation) were drawn up with a view to a new participation of CNRM and CERFACS in CMIPRead more


CERFACS Combustion paper on rocket engines selected as Distinguished Paper at the last Int. Symp. on Comb. in Adelaide

CERFACS |  14 April 2021

The paper of C. Laurent 'Heat-release dynamics in a doubly- transcritical LO2/LCH4 cryogenic coaxial jet flame subjected to fuel inflow acoustic modulation’  has been selected at the Distinguished Paper in the Gas Turbine and Rocket Engine Combustion colloquium for the 38th International Symposium on Combustion. This paper authored by Laurent, Staffelbach, Nicoud  and  T. Poinsot  is available here:  describes the first LES of a forced doubly transcritical flame.Read more

ALL NEWS