Preprints
https://doi.org/10.5194/hess-2020-668
https://doi.org/10.5194/hess-2020-668

  17 Feb 2021

17 Feb 2021

Review status: this preprint is currently under review for the journal HESS.

Technical note: Sequential ensemble data assimilation in convergent and divergent systems

Hannes Helmut Bauser1,2, Daniel Berg2,3, and Kurt Roth2,4 Hannes Helmut Bauser et al.
  • 1Biosphere 2, University of Arizona, USA
  • 2Institute for Environmental Physics (IUP), Heidelberg University, Germany
  • 3HGS MathComp, Heidelberg University, Germany
  • 4Interdisciplinary Center for Scientific Computing (IWR), Heidelberg University, Germany

Abstract. Data assimilation methods are used throughout the geosciences to combine information from uncertain models and uncertain measurement data. However, the characteristics of geophysical systems differ and may be distinguished between divergent and convergent systems. In divergent systems initially nearby states will drift apart, while they will coalesce in convergent systems. This difference has implications for the application of sequential ensemble data assimilation methods. This study explores these implications on two exemplary systems: the divergent Lorenz-96 model and the convergent description of soil water movement by the Richards equation. The results show that sequential ensemble data assimilation methods require a sufficient divergent component. This makes the transfer of the methods from divergent to convergent systems challenging. We demonstrate through a set of case studies that it is imperative to represent model errors adequately and incorporate parameter uncertainties in ensemble data assimilation in convergent systems.

Hannes Helmut Bauser et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2020-668', Anonymous Referee #1, 25 Feb 2021
    • AC1: 'Reply on RC1', Hannes H. Bauser, 20 Mar 2021
  • RC2: 'Comment on hess-2020-668', Anonymous Referee #2, 12 Apr 2021

Hannes Helmut Bauser et al.

Hannes Helmut Bauser et al.

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Short summary
Data assimilation methods are used throughout the geosciences to combine information from uncertain models and uncertain measurement data. In this study, we distinguish the characteristics of geophysical systems between divergent systems (initially nearby states will drift apart) and convergent systems (initially nearby states will coalesce) and demonstrate the implications for sequential ensemble data assimilation methods, which require a sufficient divergent component.