Articles | Volume 12, issue 4
Nonlin. Processes Geophys., 12, 515–525, 2005
https://doi.org/10.5194/npg-12-515-2005

Special issue: Nonlinear processes in solar-terrestrial physics and dynamics...

Nonlin. Processes Geophys., 12, 515–525, 2005
https://doi.org/10.5194/npg-12-515-2005

  19 May 2005

19 May 2005

Nonlinear data-assimilation using implicit models

A. D. Terwisscha van Scheltinga1 and H. A. Dijkstra2 A. D. Terwisscha van Scheltinga and H. A. Dijkstra
  • 1Institute for Marine and Atmospheric research Utrecht, Department of Physics and Astronomy, Utrecht University, The Netherlands
  • 2Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA

Abstract. We show how the traditional 4D-Var method can be adapted for implicit time-integration and extended for multi-parameter estimation. We present the algorithm for this new method, which we call I4D-Var, and demonstrate its performance using a fully-implicit barotropic quasi-geostrophic model of the wind-driven double-gyre ocean circulation. For the latter model, the different regimes of flow behavior and the regime boundaries (i.e. bifurcation points) are well known and hence the parameter estimation problem can be systematically studied. It turns out that I4D-Var is able to correctly estimate parameter values, even when background flow and "observations" are in different dynamical regimes.