Title: Data assimilation at local scale to improve CFD simulations of atmospheric dispersion: application to 1D shallow-water equations and method comparisons

Authors: Cécile L. Defforge; Bertrand Carissimo; Marc Bocquet; Patrick Armand; Raphaël Bresson

Addresses: CEREA, Joint Laboratory École des Ponts ParisTech/EDF R&D, Université Paris-Est, Marne-la-Vallée, France ' CEREA, Joint Laboratory École des Ponts ParisTech/EDF R&D, Université Paris-Est, Marne-la-Vallée, France ' CEREA, Joint Laboratory École des Ponts ParisTech/EDF R&D, Université Paris-Est, Marne-la-Vallée, France ' CEA, DAM, DIF, Chemin du Ru, 91680 Bruyères-le-Châtel, F-91297 Arpajon, France ' CEREA, Joint Laboratory École des Ponts ParisTech/EDF R&D, Université Paris-Est, Marne-la-Vallée, France

Abstract: 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. 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 representation of the atmosphere into two layers, using 1D solution of the shallow-water equations.

Keywords: data assimilation; local scale simulation; boundary conditions; shallow-water equationa; 3D-Var; back and forth nudging algorithm; iterative ensemble Kalman smoother; IEnKS; atmospheric dispersion; observations; measurements; environmental pollutions.

DOI: 10.1504/IJEP.2018.099151

International Journal of Environment and Pollution, 2018 Vol.64 No.1/2/3, pp.90 - 109

Available online: 11 Apr 2019 *

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