海洋科学学术讲座预告第342期：Dynamical Decomposition of Multiscale Oceanic Motions

报告内容简介：

Oceanic flows are characterized by a variety of dynamical regimes, with each regime encompassing multiple spatiotemporal scales. Decomposition of multiscale motions is crucial to exploring scale interaction but remains a major challenge. Conventional approaches aim at time-scale or space-scale decomposition. In this presentation, I will show how the fundamentals of ocean dynamics are introduced to propose a series of approaches which disentangle various dynamical regimes as unambiguously as possible. Specifically,

(i)    if the temporal evolution of oceanic motions is adequately given, the dynamical properties of six typical regimes (i.e., large-scale currents, barotropic tides, low-mode internal gravity waves, mesoscale flows, high-mode internal gravity waves and submesoscale flows) are fully used to decompose physical variables (e.g., sea surface height);

(ii)   if the temporal evolution is adequately given, the classic theoretical framework of vortical and wavy modes is generalized to decompose not only physical variables but also governing equations into two dynamical regimes, namely vortical (e.g., the large-scale circulation, mesoscale and submesoscale flows) and wavy (e.g., barotropic tides and internal gravity waves) motions;

(iii)  if the temporal evolution is inadequately provided, the classic theory of geostrophic adjustment is utilized to distinguish between vortical and wavy motions, based on a simultaneous snapshot of sea surface height and velocity.

The three approaches are useful for diagnostic analysis of tide-resolving model outputs; in particular, the third approach is expected to have great implications for the application of wide-swath satellite missions (e.g., Guanlan, OSCOM). It is hoped that the series of approaches will help advance the understanding of multiscale interaction in the ocean.