A multifidelity ensemble Kalman filter with reduced order control variates

AA Popov, C Mou, A Sandu, T Iliescu - SIAM Journal on Scientific Computing, 2021 - SIAM
This work develops a new multifidelity ensemble Kalman filter (MFEnKF) algorithm based on
a linear control variate framework. The approach allows for rigorous multifidelity extensions …

Ensemble variational Fokker-Planck methods for data assimilation

AN Subrahmanya, AA Popov, A Sandu - Journal of Computational Physics, 2025 - Elsevier
Particle flow filters solve Bayesian inference problems by smoothly transforming a set of
particles into samples from the posterior distribution. Particles move in state space under the …

Implicit multirate GARK methods

S Roberts, J Loffeld, A Sarshar, CS Woodward… - Journal of Scientific …, 2021 - Springer
This work considers multirate generalized-structure additively partitioned Runge–Kutta
methods for solving stiff systems of ordinary differential equations with multiple time scales …

A Bayesian approach to multivariate adaptive localization in ensemble-based data assimilation with time-dependent extensions

AA Popov, A Sandu - Nonlinear Processes in Geophysics, 2019 - npg.copernicus.org
Ever since its inception, the ensemble Kalman filter (EnKF) has elicited many heuristic
approaches that sought to improve it. One such method is covariance localization, which …

EPIRK-W and EPIRK-K Time Discretization Methods

M Narayanamurthi, P Tranquilli, A Sandu… - Journal of Scientific …, 2019 - Springer
Exponential integrators are special time discretization methods where the traditional linear
system solves used by implicit schemes are replaced with computing the action of matrix …

Multifidelity ensemble Kalman filtering using surrogate models defined by theory-guided autoencoders

AA Popov, A Sandu - Frontiers in Applied Mathematics and Statistics, 2022 - frontiersin.org
Data assimilation is a Bayesian inference process that obtains an enhanced understanding
of a physical system of interest by fusing information from an inexact physics-based model …

Investigation of nonlinear model order reduction of the quasigeostrophic equations through a physics-informed convolutional autoencoder

R Cooper, AA Popov, A Sandu - arxiv preprint arxiv:2108.12344, 2021 - arxiv.org
Reduced order modeling (ROM) is a field of techniques that approximates complex physics-
based models of real-world processes by inexpensive surrogates that capture important …

[HTML][HTML] A stochastic covariance shrinkage approach to particle rejuvenation in the ensemble transform particle filter

AA Popov, AN Subrahmanya… - Nonlinear Processes in …, 2022 - npg.copernicus.org
Rejuvenation in particle filters is necessary to prevent the collapse of the weights when the
number of particles is insufficient to properly sample the high-probability regions of the state …

The Model Forest Ensemble Kalman Filter

AA Popov, A Sandu - arxiv preprint arxiv:2210.11971, 2022 - arxiv.org
Traditional data assimilation uses information obtained from the propagation of one physics-
driven model and combines it with information derived from real-world observations in order …

Linearly implicit multistep methods for time integration

SR Glandon, M Narayanamurthi, A Sandu - SIAM Journal on Scientific …, 2022 - SIAM
Time integration methods for solving initial value problems are an important component of
many scientific and engineering simulations. Implicit time integrators are desirable for their …