Preprints
https://doi.org/10.5194/npg-2021-24
https://doi.org/10.5194/npg-2021-24

  06 Jul 2021

06 Jul 2021

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

Control Simulation Experiment with the Lorenz’s Butterfly Attractor

Takemasa Miyoshi1,2,3,4 and Qiwen Sun1,5 Takemasa Miyoshi and Qiwen Sun
  • 1RIKEN Center for Computational Science, Kobe, 650-0047, Japan
  • 2RIKEN Cluster for Pioneering Research, Kobe, 650-0047, Japan
  • 3RIKEN interdisciplinary Theoretical and Mathematical Sciences (iTHEMS), Wako, 351-0198, Japan
  • 4Application Laboratory, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, 236-0001, Japan
  • 5Department of Mathematics, Nagoya University, Nagoya, 464-8601, Japan

Abstract. In numerical weather prediction (NWP), the sensitivity to initial conditions brings chaotic behaviors and an intrinsic limit to predictability, but it also implies an effective control in which a small control signal grows rapidly to make a substantial difference. The Observing Systems Simulation Experiment (OSSE) is a well-known approach to study predictability, where “the nature” is synthesized by an independent NWP model run. In this study, we extend the OSSE and design the control simulation experiment (CSE) where we apply a small signal to control “the nature”. Idealized experiments with the Lorenz-63 three-variable system show that we can control “the nature” to stay in a chosen regime without shifting to the other, i.e., in a chosen wing of the Lorenz’s butterfly attractor, by adding small perturbations to “the nature”. Using longer-lead-time forecasts, we achieve more effective control with a perturbation size less than only 3 % of the observation error. We anticipate our idealized CSE to be a starting point for realistic CSE using the real-world NWP systems, toward possible future applications to reduce weather disaster risks. The CSE may be applied to other chaotic systems beyond NWP.

Takemasa Miyoshi and Qiwen Sun

Status: open (until 31 Aug 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on npg-2021-24', Paul PUKITE, 08 Jul 2021 reply

Takemasa Miyoshi and Qiwen Sun

Takemasa Miyoshi and Qiwen Sun

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Short summary
The weather is chaotic and hard to predict, but the chaos implies an effective control where a small control signal grows rapidly to make a big difference. This study proposes the Control Simulation Experiment where we apply a small signal to control “the nature” in a computational simulation. Idealized experiments with a low-order chaotic system show successful results by small control signals of only 3 % of the observation error. This is the first step toward the realistic weather simulations.