where z and zS are the displacements calculated
from the potential temperature and salinity fields, ′
and S′ are the potential temperature and salinity anomalies,
and @/@z and @S/@z are the mean vertical potential
temperature and salinity gradients, respectively.
For example, in MJO phase 8, the two displacement
fields (Fig. 17) are broadly consistent, in and below the
thermocline. There are negative, downward displacements
in the central Pacific, and positive, upward displacements
in the eastern Pacific. These displacements
have large amplitude, above 8 m right down to the
1400 dbar level. The two displacement fields are neither
consistent nor valid above the thermocline, as surface
fluxes and horizontal advection have a greater effect
than vertical advection on the temperature and salinity
anomalies there.