Study of Ocean and Earth Dynamics Using Satellite Altimeters

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Micro-wave radar altimeters on board satellites can measure the sea surface height globally with a ccuracy of a few centimeters, and are considered to be very useful for studies of dynamics both of the oceans and solid earth. In the present study, cooperative works between physical oceanographers and solid earth geophysicists have been intended. This program sent the Principal Investigator and several Co-Investigators to the joint TOPEX/POSEIDON and Jason-1 Science Working Team meetings held in the United States in 1998 and in France in 1999, in order to exchange information about international satellite altimetry studies. Scientific meetings were held in Fukuoka in 1998 and in Tokyo in 1999, in order to discuss about altimetry data processing and analyses. For those meetings, scientists from the Great Britain and Australia were invited in order to stimulate international cooperation. Through those activities, following progresses have been made : (1) A long time series of transport of the Kuroshio south of Japan was obtained by combined use of satellite altimetry data with in situ oceanographic data ; (2) Flow field and transport of the Oyashio and also features of surface circulations of the whole North Pacific were revealed through combined use of altimetry data with in situ oceanographic data ; (3) The scheme has been developed to assimilate the altimetry data to numerical models of the oceans, in order to obtain dynamically-consistent data sets ; (4) A precise global tide model for diurnal and semidiurnal tides was obtained from altimetry data, and also studies on long-period tides and tidal dissipation due to friction were started ; (5) Estimating the accuracy of local gravity field was mulated and also relationship between ocean variability and earth gravity variability was studied.