HYbrid Coordinate Ocean Model (HYCOM)
Entry ID:
RSMAS_HYCOM
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Summary
Abstract:
HYCOM (Bleck, 2002) is the hybrid coordinate version of MICOM. While still primarily isopycnic in character, HYCOM allows coordinate surfaces to locally deviate from isopycnals wherever the latter either fold, outcrop, or generally provide inadequate vertical resolution.
The coordinate hybridization approach in HYCOM differs from other generalized coordinate schemes developed over the years in that is does not rely on an analytic formula for specifying the depth of a given grid point. Rather, it assigns each coordinate surface a reference or "target" isopycnal and continually tries to move individual grid points which have become separated from their target isopycnal back to it. As grid points vertically migrate through the fluid, they are subjected to repelling forces from grid points above or below. These "forces" may prevent grid points from reaching their target isopycnal, but they also keep coordinate surfaces from fusing. A "pure" isopycnic model may be viewed as a hybrid model in which the repelling force is set to zero.
HYCOM, like MICOM, is a primitiveequation model containing 5 prognostic equations  two for the horizontal velocity components, a mass continuity or layer thickness tendency equation, and two conservation equations for a pair of thermodynamic variables, such as salt and temperature or salt and density.
In hydrostatic models of geophysical fluids, the mass continuity equation typically is used to infer the vertical fluid velocity from the horizontal mass flux divergence. In models where coordinate surfaces are allowed to move vertically, the vertical fluid velocity can be decomposed into the movement of the coordinate surface and the fluid velocity relative to this surface. The centerpiece of HYCOM is a "grid generator" that specifies how this decomposition is to be done at any given time and grid location. The grid generator takes into account two factors: the distance by which a coordinate surface would have to travel to merge with its target isopycnal, and the distance by which a coordinate surface can move without bumping into its nearest neighbor. By treating the sea surface as one of these neighbors, the algorithm prevents coordinate surfaces from vanishing at the geographic location where their target isopycnals outcrop; instead, HYCOM allows them to continue as fixeddepth surfaces that can be put to good use in modeling vertical mixing processes in the surface layer.
Bleck, R., 2002: An oceanic general circulation model framed in hybrid isopycnicCartesian coordinates. {\em Ocean Modelling, 4}, 5588.

Service Citation
Originators:
Bleck, R.
Title:
HYbrid Coordinate Ocean Model (HYCOM)
Release_Date:
2002
URL:
http://www.hycom.org/

Distribution Media
Distribution_Media:
Online (FTP)
Fees:
No Fee

Personnel
RAINER
BLECK
Role:
TECHNICAL CONTACT
Phone:
3053614045
Fax:
3053614696
Email:
rbleck at rsmas.miami.edu
Contact Address:
MPO Div., RSMAS
University of Miami
4600 Rickenbacker Causeway
City:
Miami
Province or State:
FL
Postal Code:
33149
Country:
USA

SCOTT
A.
RITZ
Role:
SERF AUTHOR
Phone:
3016145126
Fax:
3016145268
Email:
Scott.A.Ritz at nasa.gov
Contact Address:
NASA Goddard Space Flight Center
Global Change Master Directory
City:
Greenbelt
Province or State:
Maryland
Postal Code:
20771
Country:
USA

Publications/References
Bleck, R., and D. Boudra, 1981: Initial testing of a numerical ncean circulation model using a hybrid (quasiisopycnic) vertical coordinate. J.Phys. Oceanogr., 11, 755770.
Bleck, R., and S. Benjamin, 1993: Regional weather prediction with a model combining terrainfollowing and isentropic coordinates. Part I: Model description. Mon. Wea. Rev., 121, 17701785.
Halliwell, G., R. Bleck, and E. Chassignet, 1998: Atlantic Ocean simulations performed using a new hybridcoordinate ccean model. EOS, Trans. AGU, Fall 1998 AGU meeting.
Large, W. G., J. C. Mc Williams, and S. C. Doney, 1994: Oceanic vertical mixing: A review and a model with a nonlocal boundary layer parameterization. Rev. Geophys., 32, 363403.
Large, W.G., G. Danabasoglu, S.C. Doney, and J.C. McWilliams, 1997: Sensitivity to surface forcing and boundary layer mixing in a global ocean model: Annualmean climatology. J. Phys. Oceanogr., 27, 24182447.
Creation and Review Dates
SERF Creation Date:
20030820
SERF Last Revision Date:
20110513

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