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ERIC P. CHASSIGNET ET AL.
of the GODAE specific objectives are to apply state-of-the-art models and
assimilation methods to produce short-range open ocean forecasts, boundary
conditions to extend predictability of coastal and regional subsystems, and
initial conditions for climate forecast models (GODAE Strategic Plan,
2000). HYCOM development is the result of collaborative efforts among the
University of Miami, the Naval Research Laboratory (NRL), and the Los
Alamos National Laboratory (LANL), as part of the multi-institutional
HYCOM Consortium for Data-Assimilative Ocean Modeling funded by the
National Ocean Partnership Program (NOPP) in 1999 to develop and
evaluate a data-assimilative hybrid isopycnal-sigma-pressure (generalized)
coordinate ocean model (Bleck, 2002; Chassignet et al., 2003; Halliwell,
2004).
Traditional ocean models use a single coordinate type to represent the
vertical, but recent model comparison exercises performed in Europe
2001)
and in the U.S. (Data Assimilation and Model Evaluation Experiment -
coordinate depth, density, or terrain-following sigma can by itself be
optimal everywhere in the ocean. These and earlier comparison studies
(Chassignet et al., 1996; Roberts et al., 1996, Marsh et al., 1996) have shown
that the models considered are able to simulate the large-scale characteristics
of the oceanic circulation reasonably well, but that the interior water mass
distribution and associated thermohaline circulation are strongly influenced
by localized processes that are not represented equally by each model s
vertical discretization. The choice of the vertical coordinate system is one of
the most important aspects of an ocean model's design and practical issues of
representation and parameterization are often directly linked to the vertical
coordinate choice (Griffies et al., 2000). Currently, there are three main
vertical coordinates in use, none of which provides universal utility. Hence,
many developers have been motivated to pursue research into hybrid
approaches. Isopycnal (density tracking) layers are best in the deep stratified
ocean, z-levels (constant fixed depths) are best used to provide high vertical
resolution near the surface within the mixed layer, and V-levels (terrainfollowing) are often the best choice in shallow coastal regions. HYCOM
combines all three approaches and the optimal distribution is chosen at every
time step. The model makes a dynamically smooth transition between the
coordinate types via the layered continuity equation.
This chapter describes the various components of the HYCOM data
assimilative system and is organized as follows: an overview of the main
HYCOM characteristics is presented in section 2, the performance of the
present near real time Atlantic forecasting system is discussed in section 3
and section 4 provides an outlook.
(DYnamics of North Atlantic MOdels - DYNAMO) (Willebrand et al.,
D AMÉE) (Chassignet et al., 2000) have shown that no single vertical
,
–
–
ERIC P. CHASSIGNET ET AL.
of the GODAE specific objectives are to apply state-of-the-art models and
assimilation methods to produce short-range open ocean forecasts, boundary
conditions to extend predictability of coastal and regional subsystems, and
initial conditions for climate forecast models (GODAE Strategic Plan,
2000). HYCOM development is the result of collaborative efforts among the
University of Miami, the Naval Research Laboratory (NRL), and the Los
Alamos National Laboratory (LANL), as part of the multi-institutional
HYCOM Consortium for Data-Assimilative Ocean Modeling funded by the
National Ocean Partnership Program (NOPP) in 1999 to develop and
evaluate a data-assimilative hybrid isopycnal-sigma-pressure (generalized)
coordinate ocean model (Bleck, 2002; Chassignet et al., 2003; Halliwell,
2004).
Traditional ocean models use a single coordinate type to represent the
vertical, but recent model comparison exercises performed in Europe
2001)
and in the U.S. (Data Assimilation and Model Evaluation Experiment -
coordinate depth, density, or terrain-following sigma can by itself be
optimal everywhere in the ocean. These and earlier comparison studies
(Chassignet et al., 1996; Roberts et al., 1996, Marsh et al., 1996) have shown
that the models considered are able to simulate the large-scale characteristics
of the oceanic circulation reasonably well, but that the interior water mass
distribution and associated thermohaline circulation are strongly influenced
by localized processes that are not represented equally by each model s
vertical discretization. The choice of the vertical coordinate system is one of
the most important aspects of an ocean model's design and practical issues of
representation and parameterization are often directly linked to the vertical
coordinate choice (Griffies et al., 2000). Currently, there are three main
vertical coordinates in use, none of which provides universal utility. Hence,
many developers have been motivated to pursue research into hybrid
approaches. Isopycnal (density tracking) layers are best in the deep stratified
ocean, z-levels (constant fixed depths) are best used to provide high vertical
resolution near the surface within the mixed layer, and V-levels (terrainfollowing) are often the best choice in shallow coastal regions. HYCOM
combines all three approaches and the optimal distribution is chosen at every
time step. The model makes a dynamically smooth transition between the
coordinate types via the layered continuity equation.
This chapter describes the various components of the HYCOM data
assimilative system and is organized as follows: an overview of the main
HYCOM characteristics is presented in section 2, the performance of the
present near real time Atlantic forecasting system is discussed in section 3
and section 4 provides an outlook.
(DYnamics of North Atlantic MOdels - DYNAMO) (Willebrand et al.,
D AMÉE) (Chassignet et al., 2000) have shown that no single vertical
,
–
–