Numerical and Observational Evidence
Fig. 3.11.3c
0
I
----.
0:10/SIC
167
as shown in Fig. 3.11.5, in agreement with our expectations concerning
homogenization of unventilated layers.
The observational evidence for the existence of large zones of nearly
uniform potential vorticity on unventilated density surfaces is strong,
circumstantial evidence for the validity of the theory of potential vorticity
homogenization. It is not decisive because of our inability conclusively to test
the theoretical prediction of the structure of the zones and compare them with
observations. There may in fact be several ways to achieve uniformity on
isopycnallayers in the subtropical gyre, including layers which outcrop within
the gyre. However, the observed penetration of the circulation to density layers
well beneath those which are anywhere driven by Ekman pumping in the
subtropical gyre (especially evident in the Pacific), and the observation of
uniform q on those surfaces is a strong argument in favor of the theory.
The situation is much less clear on density surfaces which outcrop
somewhere within the region of downward Ekman velocity. These surfaces
Fig. 3.11.3c
0
I
----.
0:10/SIC
167
as shown in Fig. 3.11.5, in agreement with our expectations concerning
homogenization of unventilated layers.
The observational evidence for the existence of large zones of nearly
uniform potential vorticity on unventilated density surfaces is strong,
circumstantial evidence for the validity of the theory of potential vorticity
homogenization. It is not decisive because of our inability conclusively to test
the theoretical prediction of the structure of the zones and compare them with
observations. There may in fact be several ways to achieve uniformity on
isopycnallayers in the subtropical gyre, including layers which outcrop within
the gyre. However, the observed penetration of the circulation to density layers
well beneath those which are anywhere driven by Ekman pumping in the
subtropical gyre (especially evident in the Pacific), and the observation of
uniform q on those surfaces is a strong argument in favor of the theory.
The situation is much less clear on density surfaces which outcrop
somewhere within the region of downward Ekman velocity. These surfaces