Determination of optimal nudging coefficients

Arthur Vidard (1, 2) , François-Xavier Le Dimet (1) , Andrea Piacentini (2)

1 LMC - IMAG - Laboratoire de Modélisation et Calcul
2 CERFACS - Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique

A four-dimensional variational assimilation (4D-Var) scheme is now widely used by meteorological centres in a operational way. However, most of these applications do not take account of model error.Indeed, the classical 4D-Var with imperfect model formulation is unaffordable for current computational means. This paper presents a low-cost method for dealing with model errors in 4D variational assimilation. This method can be formally compared to a Kalman filter. This new scheme is tested on two configurations: first on a Burger equation, which allows one to calibrate the method, and second on a more relevant shallow-water equations model, both in a twin experiment framework. It is shown that, compared to classical 4D-Var results, this method provides a noticeable improvement.

Domaines: Optimisation et contrôle [math.OC]

Arthur Vidard, François-Xavier Le Dimet, Andrea Piacentini. Determination of optimal nudging coefficients. Tellus A, 2003, 55 (1), pp.1--15. ⟨10.3402/tellusa.v55i1.14576⟩. ⟨inria-00325360⟩