558
equations, i.e. the ‘split-explicit’ formulation popular in free surface ocean
models. Conservative parabolic-spline discretization in the vertical
significantly reduces the pressure-gradient truncation error that has
previously plagued terrain-following coordinate models.
Tangent linear and adjoint versions of ROMS have been developed and
are being turned to applications including sensitivity analysis, stability
analysis, ensemble prediction and variational data assimilation (Moore et al.
2004). The ROMS code has been structured for efficient performance on
parallel-computing platforms (using MPI or OpenMP).
The parameterization of vertical turbulence in coastal models can have
ramifications for details or even some qualitative features of the flow,
especially the transport of suspended matter and sediments (Durski et al.
2004, Wijesekera et al. 2003, Warner et al. 2005). Among the options for the
parameterization of vertical mixing in ROMS are the k-profile
parameterization (KPP) of Large et al. (1994), the level 2½ Mellor and
Yamada (1982) scheme, and the suite of two-equation closures (one
equation for turbulence kinetic energy and a second equation for a generic
turbulence length scale quantity) proposed by Umlauf and Burchard (2003)
that implement the widely used k-epsilon and k-omega closures, and a
revised form of k-kl (Mellor-Yamada level 2½). The two-equation closures
are completed by stability functions based on the parameterizations of
Galperin et al. (1988), Kantha and Clayson (1994), or Canuto et al. (2001).
As an adjunct to vertical turbulence closure, the parameterization of bottom
boundary stress includes, optionally, quadratic drag or the effects of wavecurrent interaction, moveable beds, and ripples (Soulsby 1995, Harris and
Wiberg 2001, Li and Amos 2001). This implementation of an extensive suite
of turbulence closures in a single 3-dimensional ocean model allows the
systematic comparison of the schemes in the context of the CBLAST
observations.
3.2
ROMS modeling for CBLAST
In order to make a meaningful comparison of the CBLAST-Low
observations with the modeled regional heat budget, ROMS must capture the
essential features of the 3-dimensional heat transport on diurnal to several
day time-scales, and spatial scales of order a few kilometers. To achieve this
objective, we have employed a high degree of realism in the configuration of
model bathymetry and forcing. The model has fine grid spacing (1 km) and
realistic bathymetry from a 3-arc-second Coastal Relief Model (NGDC,
2004). Open boundary conditions are specified following the method of
Marchesiello et al. (2001): Orlanski-type radiation is applied to tracers and
baroclinic velocity in conjunction with relaxation (with timescale of 0.5 days
on inflow and 10 days on outflow) to a regional bi-monthly climatology of
shelf circulation from the semi-diagnostic model of Naimie et al. (1994).
JOHN L. WILKIN AND LYON LANEROLLE
equations, i.e. the ‘split-explicit’ formulation popular in free surface ocean
models. Conservative parabolic-spline discretization in the vertical
significantly reduces the pressure-gradient truncation error that has
previously plagued terrain-following coordinate models.
Tangent linear and adjoint versions of ROMS have been developed and
are being turned to applications including sensitivity analysis, stability
analysis, ensemble prediction and variational data assimilation (Moore et al.
2004). The ROMS code has been structured for efficient performance on
parallel-computing platforms (using MPI or OpenMP).
The parameterization of vertical turbulence in coastal models can have
ramifications for details or even some qualitative features of the flow,
especially the transport of suspended matter and sediments (Durski et al.
2004, Wijesekera et al. 2003, Warner et al. 2005). Among the options for the
parameterization of vertical mixing in ROMS are the k-profile
parameterization (KPP) of Large et al. (1994), the level 2½ Mellor and
Yamada (1982) scheme, and the suite of two-equation closures (one
equation for turbulence kinetic energy and a second equation for a generic
turbulence length scale quantity) proposed by Umlauf and Burchard (2003)
that implement the widely used k-epsilon and k-omega closures, and a
revised form of k-kl (Mellor-Yamada level 2½). The two-equation closures
are completed by stability functions based on the parameterizations of
Galperin et al. (1988), Kantha and Clayson (1994), or Canuto et al. (2001).
As an adjunct to vertical turbulence closure, the parameterization of bottom
boundary stress includes, optionally, quadratic drag or the effects of wavecurrent interaction, moveable beds, and ripples (Soulsby 1995, Harris and
Wiberg 2001, Li and Amos 2001). This implementation of an extensive suite
of turbulence closures in a single 3-dimensional ocean model allows the
systematic comparison of the schemes in the context of the CBLAST
observations.
3.2
ROMS modeling for CBLAST
In order to make a meaningful comparison of the CBLAST-Low
observations with the modeled regional heat budget, ROMS must capture the
essential features of the 3-dimensional heat transport on diurnal to several
day time-scales, and spatial scales of order a few kilometers. To achieve this
objective, we have employed a high degree of realism in the configuration of
model bathymetry and forcing. The model has fine grid spacing (1 km) and
realistic bathymetry from a 3-arc-second Coastal Relief Model (NGDC,
2004). Open boundary conditions are specified following the method of
Marchesiello et al. (2001): Orlanski-type radiation is applied to tracers and
baroclinic velocity in conjunction with relaxation (with timescale of 0.5 days
on inflow and 10 days on outflow) to a regional bi-monthly climatology of
shelf circulation from the semi-diagnostic model of Naimie et al. (1994).
JOHN L. WILKIN AND LYON LANEROLLE