Abstract
This paper investigates the relationship between a Stochastic Grid
Perturbation (SGP) and Location Uncertainty (LU). The LU formulation,
which introduces random velocity fluctuations, has shown efficacy in
organizing large-scale flow and replicating long-term statistical
characteristics. SGP was created as a simpler approach which perturbs
the computational grid for ensemble members, aiming to simulate small
uncertainties in high-resolution predictability studies. We aim to
clarify the link between SGP and LU. After introducing the LU formalism,
we derive the SGP method and discuss its connection to LU. Correlated
noise in time is introduced in the SGP method to preserve the structure
of the original grid. A compensating advection term is shown to preserve
LU properties despite the latter correlated noise. Numerical experiments
on a 3-layer Quasi-Geostrophic model compare various SGP implementations
with an explicit LU implementation, highlighting the importance of the
compensating advection term to achieve strict equivalence.