Atmospheric dispersion modelling requires meteorological inputs over local domains with possibly complex topographies. These local wind fields may be difficult to simulate with CFD models, in particular because of their sensitivity to geometrical features and to model inputs, especially the boundary conditions which are generally provided by larger-scale models or measurements. Using data assimilation, a few measurements inside the domain could add information to the imprecise boundary conditions and thus greatly enhance the precision of the dispersion simulations.

This is problem that Cécile Defforge, Bertand Carissimo, Patrick Armand, Raphaël Bresson and I tackled in a new paper to appear in the International Journal of Environmental Pollution. Three data assimilation techniques (3DVar, the back and forth nudging algorithm, and the iterative ensemble Kalman smoother) have been adapted to local scale simulations by taking boundary conditions into account instead of initial conditions for which they are usually applied. Their performances have been evaluated at small scales, with a simple flow, using 1D solution of the shallow water equations.

This study is meant to prepare the application of data assimilation using a realistic CFD model (Code_Saturne, the EdF multi-purpose CFD code) over a wind farm field to estimate the wind energy potential.