2004 LOM Workshop

Monday 9:15 - 9:35 a.m.

HIM algorithmic developments required to make GFDL's global isopycnal ocean model work

Robert Hallberg
NOAA/GFDL
Robert.Hallberg@noaa.gov

ABSTRACT

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GFDL is in the process of building an IPCC-class coupled model using a global version of HIM at 1-degree, 48 layer resolution. In the course of this exercise, a number of algorithmic improvements have proven necessary. This talk will briefly cover several of these; some are brief updates on topics discussed in past LOM workshops. The pressure gradient formulation has been changed to avoid the thermobaric instability that arises in global isopycnal models with high resolution in density space and the full nonlinear equation state. This is the resolution to the problem discussed at the 2003 LOM workshop. An additional source of bottom mixing from the energy extracted by the bottom drag has proven necessary to avoid having thin, viscous plumes of overflow water sink to the bottom of the ocean. The use of a 2-layer refined bulk mixed layer enables shear-driven restratification and Ekman restratifation and destabilization, and may reduce the differences in the mixed layer dynamics between traditional bulk mixed layers and pressure-space hybrid coordinate mixed layers. Changes in the reconsilation of the internal and external estimates of the free surface height may also be described. The simulations generated by this model will be described in a separate talk by B. Arbic.

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LOM Users' Workshop, February 9-11, 2004