|dc.description.abstract||A portion of the northeast Pacific ocean was chosen within which to evaluate and
use altimetric data from the U.S. Navy Geodetic Satellite GEOSAT. The zero-order
accuracy of the major GEOSAT geophysical data record (GDR) channels was verified, and
occasional gaps in the altimeter coverage were noted. GEOSAT'S 17-day repeat orbit
allowed use of collinear-track processing to create profiles of the difference between the sea
surface height along a given satellite repeat, and the mean sea surface height along that
repeat's groundtrack. Detrending of sea surface bias and tilt on each repeat reduced orbit
and other long wavelength errors in the difference profiles.
The corrections provided on the GEOSAT GDR were examined for their effects on
the difference profiles of three test arcs. It was found that only the ocean tide,
electromagnetic bias, and inverted barometer corrections varied enough over the arc lengths
(~4400 km) to have any noticeable effect on the difference profiles. Only the ocean tide
correction was accurate enough to warrant using it to adjust the sea surface heights. The
recommended processing of GEOSAT data for the area included making the ocean tide
correction, three-point block averaging successive sea surface heights, and forming the
mean height profiles from 18 repeat cycles (to reduce aliasing of the M2 tidal component).
A set of difference proftles for one GEOSAT arc indicated that a reasonable estimate of
GEOSAT's system precision was -4.5 cm (RMS). The mid wavelength range (100-500
km) of these profiles was found to be the only range in which oceanic mesoscale features
could be separated from altimeter errors.
Mean alongtrack wavenumber spectra of oceanic variability for two GEOSAT arcs
were compared with a SEASAT-derived regional spectrum of Fu (1983). Agreement was
good, with GEOSAT showing less system noise at short wavelengths, and greater oceanic
variability at long wavelengths. The GEOSAT spectra were fit well by a k-1.5 slope at
wavelengths from 100 to 1000 km.
Sea surface temporal variability as a function of location was compared with the
SEASAT results of Cheney et al. (1983). Qualitative agreement was excellent and
quantitative differences were largely accounted for. GEOSAT picked up the variability of
the major current systems of the northeast Pacific, including the Alaskan, Californian, and
North Equatorial currents. Error bounds on GEOSAT-derived oceanic variability showed
that the effects of uncorrected electromagnetic bias, inverted barometer, and wet
troposphere were significant. Further work in the areas of error modelling, orbit
determination, and geoid calculation were called for.||en_US||