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Data Assimilation and Optimization

The development of data assimilation methods and optimization algorithms is of particular interest for applications in the Earth sciences, aerodynamics and space dynamics.

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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.

cmaes_mean_meanOptimization 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.

 

Applications in data assimilation :fig_da_website

Hydrology/hydraulics: Water resource management and flood risk monitoring associated with the dynamics of continental waters are of first importance for public safety and financial . Flood and inundation forecasting relies on numerical modeling tools for hydraulics and hydrology combined with a wide range of observations (in situ and spaceborne). CERFACS is developing in collaboration with EDF, CNES, SCHAPI, CNRM, …, variational and ensemble data assimilation methods based on hydrologic/hydraulic solvers (among whom MASCARET and TELEMAC-2D). These implementations are part of active research activities and of their transfer to operational level.

Wildfires: Real-time prediction of wildfire spread and emissions has been identified as a valuable rsearch objective with direct applications in both fire risk management, fire emergency response and fire-induced environmental impact in the context of climate change. The predictive capability for wildfire behavior at regional scales relies on a semi-empirical modeling of a propagating front (i.e. interface between burnt and unburnt areas) at land surface, which involves biomass, topographical and meteorological data that are embedded with uncertainties. CERFACS is currently developing in collaboration with UMD and SPE an ensemble-based data assimilation system named FIREFLY, in order to sequentially estimate input parameters and the simulated fire front position when fire front position observations are available and thereby to improve the forecast performance of fire spread models.

NEWS

Young PhD day (JDD) – Thursday 8 October 2020

Brigitte Yzel |  24 September 2020

  Ph.D. Students' Day (JDD 2020) Thursday 8 October 2020 Virtual event open to our partners and associates   Planning   The 2020 edition of the PhD Students' Day will take place on October 8th, 2020. This year, this day of the PhD students of the Cerfacs, will take place mainly in visio in order to respect all the health safety measures relating to Covid-19. This day will be held in a virtual way through oral presentations filmed and broadcast on a private link, which we will distribute to all participants. Everyone will thus be able to discover at a distance the subjects developed by the doctoral students. At the same time, the "Posters session" will be opened on the morning of the JDD, by sending all the posters in pdf format by e-mail to all the participants for consultation, and by opening the "50-minute question session" on a channel whose links we will send you. This will allow participants to ask questions about the posters of the session. Finally, we have included in this 5th edition a great novelty, by allowing several students to present their subject in the popularised form of "My thesis in 3 minutes", guided by Matthieu Pouget, actor and theatre director. This day will end with the vote for the "Best poster" and the "Best presentation of My thesis in 3 minutes". Participation in the event is free of charge. However, for logistical reasons, registration, only by invitation, is mandatory.   Organising Committee:  Scientific committee  Nicolas Venkovic Victor Xing Inscription &  information Jade Schweiger Brigitte Yzel  Read more


Sparse Days 2020, Cerfacs

Brigitte Yzel |  24 September 2020

Sparse Days Meeting 2020  23 - 24 November 2020 Virtual Workshop   The annual Sparse Days meeting will be held this year as a virtual event, on 23 - 24 November 2020. Sadly, because of the pandemic, we will not be able to have a normal face-to-face Sparse Days at Cerfacs this year. We will be holding an online version from 3pm to 7pm on 23 and 24 November. The timing is chosen to accommodate participants from North America since, at normal Sparse Days, we have a good representation from there. A registration form  is available on this conference website where you can also submit a title and an abstract for any proposed talk. We will probably be using the Webex system and will post details about how to connect to all people who register.Read more

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