Derivation and Numerical Assessment of a Stochastic Large-Scale
Hydrostatic Primitive Model
Abstract
Forces that govern the motion of planetary flows originate from
interactions occurring at scales that are orders of magnitude smaller
than the flow itself. These mesoscale and sub–mesoscale eddies
contribute to large-scale flow mixing, particle entrainment, and tracer
transport. Therefore, oceanic simulations must accurately characterize
their contributions to capture the flow dynamics. In this work, a
stochastic representation of the primitive equations, derived within the
framework of modeling under location uncertainty (LU), is proposed. This
framework decomposes the velocity into a smooth–in–time
large–scale component and a random field, accounting for unresolved
mesoscale and sub–mesoscale motions. The LU framework is unique in
its derivation, as it is obtained from physical conservation principles
through a stochastic version of the Reynolds transport theorem. Two
data-driven approaches are developed to model the random noise using
proper orthogonal decomposition and dynamic mode decomposition methods.
For higher resolution, model based noise as well as mixture of model
based and data driven noise with observational constraints are proposed
and compared. Numerical simulations demonstrate that the LU framework
improves flow prediction for gyre circulation compared to its
deterministic counterpart. Enhanced flow mixing, jet characteristics,
and tracer transport are observed. Additionally, terms in the LU
framework are analyzed for their contribution to structuring the flow.