“…For model order reduction of SPDEs, classic methods such as polynomial chaos Downloaded 12/12/18 to 18.51.0.96. Redistribution subject to SIAM license or copyright; see http://www.siam.org/journals/ojsa.php [56,28,84,13], proper orthogonal decomposition (POD) [26,60], dynamic mode decomposition (DMD) [61,66,78,82,31], and stochastic Galerkin schemes and adjoint methods [10,7] assume a priori choices of time-independent modes \bfitu i (\bfitx ) and/or rely on Gaussianity assumptions on the probability distribution of the coefficients \zeta i . For example, the popular data POD [26] and DMD [66] methods suggest extracting timeindependent modes \bfitu i (\bfitx ) that respectively best represent the variability (for the POD method) or the approximate linear dynamics (for the DMD method) of a series of snapshots \bfitu (t k , \bfitx , \omega 0 ) for a given observed or simulated realization \omega 0 .…”