Geophysical flows under location uncertainty, Part II Quasi-geostrophy and efficient ensemble spreading. Issue 3 (4th May 2017)

• Record Type: Journal Article
• Authors: Resseguier, V.; Mémin, E.; Chapron, B.
• Is Part Of: Geophysical and astrophysical fluid dynamics. Volume 111:Issue 3(2017)
• Page Start: 177
• Page End: 208
• Publication Date: 2017-05-04
• Subjects: Stochastic sub-grid parameterization -- Uncertainty quantification -- ensemble forecasts; Fluid dynamics -- Periodicals; Astrophysics -- Periodicals; Geophysics -- Periodicals; 551
• DOI: 10.1080/03091929.2017.1312101
• Languages: English
• ISSNs: 0309-1929

Abstract

Abstract : Models under location uncertainty are derived assuming that a component of the velocity is uncorrelated in time. The material derivative is accordingly modified to include an advection correction, inhomogeneous and anisotropic diffusion terms and a multiplicative noise contribution. In this paper, simplified geophysical dynamics are derived from a Boussinesq model under location uncertainty. Invoking usual scaling approximations and a moderate influence of the subgrid terms, stochastic formulations are obtained for the stratified Quasi-Geostrophy and the Surface Quasi-Geostrophy models. Based on numerical simulations, benefits of the proposed stochastic formalism are demonstrated. A single realization of models under location uncertainty can restore small-scale structures. An ensemble of realizations further helps to assess model error prediction and outperforms perturbed deterministic models by one order of magnitude. Such a high uncertainty quantification skill is of primary interests for assimilation ensemble methods. MATLAB ® code examples are available online.