Abstract

Data assimilation addresses the general problem of how to combine model-based predictions with partial and noisy observations of the process in an optimal manner. This survey focuses on sequential data assimilation techniques using probabilistic particle-based algorithms. In addition to surveying recent developments for discrete- and continuous-time data assimilation, both in terms of mathematical foundations and algorithmic implementations, we also provide a unifying framework from the perspective of coupling of measures, and Schrödinger’s boundary value problem for stochastic processes in particular.

Highlights

  • This survey focuses on sequential data assimilation techniques for state and parameter estimation in the context of discrete- and continuous-time stochastic diffusion processes

  • In addition to surveying recent developments for discrete- and continuous-time data assimilation, both in terms of mathematical foundations and algorithmic implementations, we provide a unifying framework from the perspective of coupling of measures, and Schrodinger’s boundary value problem for stochastic processes in particular

  • We find that M ≥ Meff ≥ 1 an√d the accuracy of a data assimilation step decreases with √decreasing Meff, that is, the convergence rate 1/ M of a standard Monte Carlo method is replaced by 1/ Meff (Agapiou, Papaspipliopoulos, Sanz-Alonso and Stuart 2017)

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Summary

Introduction

This survey focuses on sequential data assimilation techniques for state and parameter estimation in the context of discrete- and continuous-time stochastic diffusion processes. We will view such interacting particle systems in this review from the perspective of approximating a certain boundary value problem in the space of probability measures, where the boundary conditions are provided by the underlying stochastic process, the data, and Bayes’ theorem This point of view leads naturally to optimal transportation (Villani 2003, Reich and Cotter 2015) and, more importantly for this review, to Schrodinger’s problem (Follmer and Gantert 1997, Leonard 2014, Chen, Georgiou and Pavon 2014), as formulated first by Erwin Schrodinger in the form of a boundary value problem for Brownian motion (Schrodinger 1931). M , is generally assumed to be small to moderate relative to the number of variables of interest, we will focus on robust but generally biased particle methods

Overall organisation of the paper
Summary of essential notations
Mathematical foundation of discrete-time DA
Prediction
Gaussian model error
SDE models
Filtering and Smoothing
Schrodinger Problem
Discrete measures
Numerical methods
Filtering
Smoothing
DA for continuous-time data
Smooth data
Random data
Ensemble Kalman–Bucy filter
Feedback particle filter
Conclusions
Full Text
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