Abstract:

An ocean acoustic tomography experiment was performed with a pair of 200-Hz transceivers in the western equatorial Pacific along the longitudinal line of 147.5 (degrees)E during April--December 1996. Time series of reciprocal ray travel times were obtained at about the 700-km range for approximately 100 days between the transceivers. The one-direction, resolved-ray travel times were applied to obtain temperature, and differential resolved-ray travel times to obtain barotropic current velocity. The inversions derived from the stochastic inverse method gave a series of snapshots of two-dimensional temperature fields, which showed a pattern similar to that determined from CTD measurements during the transceiver deployment cruise. The range-averaged temperature anomaly, (delta)T(z), agreed almost perfectly with that calculated from the difference between the CTD temperature profile and the NODC reference temperature profile within an estimated error of (plus or minus)0.5 (degrees)C, except for the surface layer. The evolution of acoustically determined range-averaged temperature and temperature anomaly structures agreed well with the concurrent PMEL/TAO array data. A range-averaged barotropic current determined from the difference of the reciprocal ray travel times also agreed with the range- and depth-averaged meridional velocity determined from ADCP measurements during the transceiver deployment cruise in the same order.