The effects of stratification on flow separation
Journal of the Atmospheric Sciences 62:7 II (2005) 2618-2625
Abstract:
Separation of stratified flow over a two-dimensional hill is inhibited or facilitated by acceleration or deceleration of the flow just outside the attached boundary layer. In this note, an expression is derived for this acceleration or deceleration in terms of streamline curvature and stratification. The expression is valid for linear as well as nonlinear deformation of the flow. For hills of vanishing aspect ratio a linear theory can be derived and a full regime diagram for separation can be constructed. For hills of finite aspect ratio scaling relationships can be derived that indicate the presence of a critical aspect ratio, proportional to the stratification, above which separation will occur as well as a second critical aspect ratio above which separation will always occur irrespective of stratification. © 2005 American Meteorological Society.Three-dimensional unstructured mesh ocean modelling
Ocean Modelling 10:1-2 SPEC. ISS. (2005) 5-33
Abstract:
In this article the advantages and current status of unstructured mesh ocean modelling are reviewed. Future challenges are discussed along with the potential of resulting methods to make a significant impact on ocean modelling over the next decade. These methods are important because they are the only techniques that can simultaneously resolve both small and large scale ocean flows while smoothly varying resolution and conforming to complex coastlines and bathymetry. Realising the full potential of such methods will necessitate the use of dynamic mesh adaptivity. A number of techniques need to be combined and developed from different numerical modelling and geophysical fluid dynamics disciplines in order to create a powerful unstructured mesh ocean model. These are: Accurate and robust methods for the discretisation and advection of tracers, density and momentum; the choice of element/cell and satisfaction of the LBB stability condition; representation of hydrostatic and geostrophic balance; the ability to deal with sigma coordinate-like errors associated with the use of unstructured meshes; initial mesh generation to follow complex bathymetry and coastlines; sub-grid scale modelling on unstructured and possibly solution adaptive meshes; scalable solvers and parallel computing. A good solution to each problem is required, and thus the resulting model may be argued to be considerably more complex than traditionally used structured mesh models. It is these topics that are addressed here. © 2004 Elsevier Ltd. All rights reserved.Deep-Sea Research Part II: Preface
Deep-Sea Research Part II: Topical Studies in Oceanography 51:25-26 SPEC. ISS. (2004) 2881
Small and mesoscale processes and their impact on the large scale: An introduction
Deep-Sea Research Part II: Topical Studies in Oceanography 51:25-26 SPEC. ISS. (2004) 2883-2887
Abstract:
Great progress has been made in understanding the role of small- and mesoscale processes on the large-scale structure and circulation of the oceans. However, many questions remain regarding the sensitivity of the large-scale ocean circulation and hence the earth's climate, to rates of stirring, mixing, and dissipation supported by ocean eddies, internal waves, and boundary layers. Although such relatively small-scale oceanic phenomena are ubiquitous, we lack detailed knowledge about their interaction with the large-scale motions, as well as their interactions amongst themselves. Contributions are presented from observational, theoretical, and modeling studies that focus on small- and mesoscale ocean processes, and some parameterizations of these processes for use in studies of the large-scale circulation. The range of topics is relatively broad, with most focus on internal wave generation, flow-topography interaction, and small- and mesoscale processes involved in ocean mixing. General conclusions emphasize the notion of localized mixing and the importance of interaction between waves, eddies, and topography, and the importance of interactions between oceanic motions and the background density stratification. © 2004 Elsevier Ltd. All rights reserved.Global teleconnections of meridional overturning circulation anomalies
Journal of Physical Oceanography 34:7 (2004) 1702-1722