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SEQUOIA data assimilation platform

A platform for joint assimilation to all developments in data assimilation to SIROCCO, SEQUOIA system (SEQUential Optimization, Initialization and Analysis) has been developed since 2002. It benefit from the legacy system SOFA (System for Ocean Forecasting and Analysis) used in various stages of development by several operational systems: MERCATOR (De Mey, 1998), MFS (De Mey and Benkiran 2002) ADRICOSM (Castellari and al., 2006).

In addition to implementation according to current standards (Fortran-95, modularity, etc.) SEQUOIA adapts equally to structured grids (finite difference) or not (elements / finite volume) via a generalized grid system. Its streamlined interface with the digital model enables it to drive any model (currently S model, MOG2D / T-UGOm and POLCOMS are interfaced, and other models are being considered). The code also manages the overall simulation on cluster PCs or remote machine.

The system analysis interchangeable cores can implement several assimilation schemes. These cores are part of SEQUOIA and have the same status - free software, access to sources, GNU GPL. Three analytical cores have been developed to date for SEQUOIA:

  • Mantaray, a core EOFs 3-D near SEEK (used as part of the thesis of G. and J. Jordà Lamouroux and several post-docs)
  • SOFA, a core EOFs 1-D which incorporates the ideas of the original code SOFA mentioned above (used in the industrial and operational partnerships)
  • BELUGA, a full row of core fixed in the dual space.

Typically, we use SEQUOIA in the following modes, although other uses are possible a priori:

  • Ensemble Optimal Interpolation (ENOI) - to order reduced with Mantaray analysis cores or SOFA
  • Ensemble Kalman Filter (EnKF) and Ensemble Kalman Smoother (EnKS) with the BELUGA analysis core.

Highlights:

  • Stable version of Availability
  • Complete assimilation code (not just the algebraic part)
  • Experience SOFA used in operating
  • Industrial and operational partnerships
  • Anchoring in international projects (MERSEA, MFS, ECOOP, MyOcean GODAE OceanView, ESA GOCEAN)
  • Multi-grid, multi-algebra, multi-model
  • Modern coding f90 / 95; dynamic allocation of memory; Search by binary trees; etc.
  • Resolution on workstation or PC cluster.