THE NEAR-SURFACE LAYER OF THE OCEAN
eddies, then smaller scales on which rotational effects are less effective
become more important to parameterize.
7.6.3 Interactions
While some subgrid processes have been parameterized, the interactions
among these processes are generally not considered. For example, due to
freshwater cycling and salinity effects, a salt-stratified barrier layer
(Lindstrom and Lukas, 1991) may exist over a broad region covering many
grid points in a numerical model. But the barrier layer is maintained by the
interaction of resolved processes and unresolved processes acting on subgrid
scales (Vialard and Delecluse, 1998b). The subduction process that plays a
role in barrier layer maintenance involves large-scale advection, but also
involves small-scale frontal processes including subgrid vertical and
horizontal mixing.
The barrier layer favors the maintenance and displacement of the warm
pool into the central Pacific by isolating the mixed layer from entrainment
cooling and by confining the response of westerly wind events to a relatively
shallow mixed layer (Vialard and Delecluse, 1998a). This process is an
can also be important in the dynamics of coastal regions with river run-off
(like the Bay of Bengal) and in the marginal polar seas under conditions of
ice melting.
Vinayachandran et al. (2002) captured the formation of a barrier layer at
17°30’N, 89°E in the northern Bay of Bengal. On 28 July 1999, the upper 30
m layer was homogeneous in both temperature and salinity (Figure 1-18).
Subsequently, a freshwater plume from river discharge and rainfall was
advected to the experimental area. The arrival of the freshwater plume
caused the depth of the mixed layer to decrease to about 10 m and the
salinity in the surface layer to drop by about 4 psu. As a result, a new
halocline and thus a barrier layer formed within the upper 30 m of the ocean
(Figure 7-27.). Air-sea interaction was then restricted to this thinner mixed
layer; a 0.5°C inversion in temperature just below the mixed layer provided
evidence that the surface cooling was restricted to this thin layer.
Such a thin surface layer is more strongly coupled to the atmosphere. The
salt-stratified barrier layer may thus be involved in the processes of deep
atmospheric convection and cyclogenesis by reducing the entrainment
cooling from below the mixed layer (Murty et al., 2002; Subrahmanyam et
al., 2005).
502
important part of the ENSO cycle (Maes et al., 2003; see Section 1.7.4). It
eddies, then smaller scales on which rotational effects are less effective
become more important to parameterize.
7.6.3 Interactions
While some subgrid processes have been parameterized, the interactions
among these processes are generally not considered. For example, due to
freshwater cycling and salinity effects, a salt-stratified barrier layer
(Lindstrom and Lukas, 1991) may exist over a broad region covering many
grid points in a numerical model. But the barrier layer is maintained by the
interaction of resolved processes and unresolved processes acting on subgrid
scales (Vialard and Delecluse, 1998b). The subduction process that plays a
role in barrier layer maintenance involves large-scale advection, but also
involves small-scale frontal processes including subgrid vertical and
horizontal mixing.
The barrier layer favors the maintenance and displacement of the warm
pool into the central Pacific by isolating the mixed layer from entrainment
cooling and by confining the response of westerly wind events to a relatively
shallow mixed layer (Vialard and Delecluse, 1998a). This process is an
can also be important in the dynamics of coastal regions with river run-off
(like the Bay of Bengal) and in the marginal polar seas under conditions of
ice melting.
Vinayachandran et al. (2002) captured the formation of a barrier layer at
17°30’N, 89°E in the northern Bay of Bengal. On 28 July 1999, the upper 30
m layer was homogeneous in both temperature and salinity (Figure 1-18).
Subsequently, a freshwater plume from river discharge and rainfall was
advected to the experimental area. The arrival of the freshwater plume
caused the depth of the mixed layer to decrease to about 10 m and the
salinity in the surface layer to drop by about 4 psu. As a result, a new
halocline and thus a barrier layer formed within the upper 30 m of the ocean
(Figure 7-27.). Air-sea interaction was then restricted to this thinner mixed
layer; a 0.5°C inversion in temperature just below the mixed layer provided
evidence that the surface cooling was restricted to this thin layer.
Such a thin surface layer is more strongly coupled to the atmosphere. The
salt-stratified barrier layer may thus be involved in the processes of deep
atmospheric convection and cyclogenesis by reducing the entrainment
cooling from below the mixed layer (Murty et al., 2002; Subrahmanyam et
al., 2005).
502
important part of the ENSO cycle (Maes et al., 2003; see Section 1.7.4). It