Further analyses towards the introduction of ocean circulation model information into geopotential solutions

Two representation methods for the Dynamic Ocean Topography (DOT)
are commpared. One uses surface spherical harmonics, the other Proudman functions,
which form an ocean domain-specific orthonormal basis. The DOT implied by the
temporally averaged output of the POCM-4B ocean circulation model, provided the
data for the implementation and testing of the two methods. Using these data a
spherical harmonic representation was developed, to degree 30, and a Proudman
function decomposition employing 961 basis vectors, so that both representations
involve an equal number of parameters. The input DOT field had an rms valur of
±66.6 cm. The recovered rms DOT was ±66.1 cm for the spherical harmonic case,
±66.3 cm for the Proudman function case, while the rms difference between the two
cases was ±4,2 cm. Although in an overall sense the two representations (with equal
number of parameters) yield similar results, in the proximity of the ocean domain
boundary the Proudman functions approximate the input DOT field better than the
surface spherical harmonics.