Previous Abstract | Back to Abstracts Page | Next Abstract
Use of in-situ density in isopycnic-coordinate ocean models
Rainer Bleck
NASA Goddard Institute or Space Studies, New York, NY
(Abstract received 04/26/2015 for session X)
ABSTRACT
Attempts to align coordinate layers with neutral surfaces in ocean models to reduce numerically induced diapycnal mixing have led to the development of isopycnic and hybrid-isopycnic coordinate models such as MICOM and HYCOM. The principal problem in solving the dynamic equations in sloping coordinate layers lies in the computation of the horizontal pressure gradient force -- the so-called 2-term PGF problem. Isopycnic models traditionally overcome it by (1) treating the ocean as incompressible and (2) using a globally reference potential density, rather than in-situ density, as buoyancy-controlling variable (Spiegel and Veronis, 1960). In 2008, Adcroft et al. suggested a novel approach that overcomes numerical stability problems associated with using in-situ density by computing the PGF very precisely in finite-volume form. Their approach in principle decouples the placement of coordinate layers (still guided by the desire to align them with neutral surfaces) from the dynamic calculations. Attempts to introduce this scheme into HYCOM have only been partially successful so far, the main drawback being the gradual formation of "varicose" coordinate layers at mid-depth in multi-year simulations.
Previous Abstract | Back to Abstracts Page | Next Abstract
2015 LOM Workshop, Copenhagen, Denmark June 2nd - 4th, 2015