Abstract
To improve the geoid profile in the region south of Japan as accurate enough to detect geostrophic
currents, oceanographic observations along the ground tracks of TOPEX/POSEIDON
including CTD casts and an IES (Inverted Echo Sounder) measurement at a point south off the
Kuroshio were carried out for the period from November 1992 to May 1994. It is suggested that
the warm water off the Kuroshio south of Cape Ashizuri piled up in November 1993, when the
travel time observed with IES was shorter than other period. By comparing the time series of IES
travel time, dynamic heights calculated from CTD casts at the mooring point of IES, and
altimetric sea surface heights (ASSH)obtained by TOPEX/POSEIDON, it is shown that the rela
tionship between IES travel time and dynamic heights from CTD is almost linear; the correlation
coefficient is about 0.99. It is also pointed out that the altimeter of TOPEX/POSEIDON accu
rately observes temporal variation of the dynamic height, because ASSH and IES time series
shows rather good correlation. Spatial profiles of ASSH using available geoid models, however,
are not reliable enough to detect the Kuroshio paths, because mean sea surface in the MGDR
(Merged Geophysical Data Record) data set distributed from the Jet Pulsesion Laboratory or
other geoid models still containanacceptable error of 20 cm or more. Corrections for ASSHto
determine the Kuroshio paths by satellite altimeterare madeby means of comparingASSH and
dynamic heights obtained from in situ CTD. The accuracy of ASSH after correction is estimated
to be less than 10cm.
