Hierarchical Bayesian inversion of global variables and large-scale
spatial fields
Abstract
Bayesian inversion is commonly applied to quantify uncertainty of
hydrological variables. However, the focus in Bayesian inversion is more
on spatial hydrological properties instead of hyperparameters or
global/non-gridded variables. In this paper, we present a hierarchical
Bayesian framework to quantify uncertainty of both global and spatial
variables. We estimate first the posterior of global variables and then
hierarchically estimate the posterior of the spatial field. We propose a
machine learning-based inversion method to estimate the joint
distribution of data and global variables directly without introducing a
statistical likelihood. We also propose a new local dimension reduction
method: local principal component analysis (local PCA) to update
large-scale spatial fields with local data more efficiently. We
illustrate the hierarchical Bayesian formulation with two case studies:
one with a linear forward model (volume averaging inversion) and a
second with a non-linear forward model (pumping tests). Results show
that quantifying global variables uncertainty is critical for assessing
uncertainty on predictions. We show how the local PCA approach
accelerates the inversion process. Furthermore, we provide an
open-source Python package on the hierarchical Bayesian framework
including two case studies.