A global least-squares method was used to fit 12-day blocks of travel time data to a regional quasi-geostrophic model, and then the model was used to forecast data beyond the initialization period. The hypothesis to be checked is that the evolution of the eddies is given accurately by quasi-geostrophic dynamics, which simplifies the calculations but which excludes applications to observations from regions with large stratification changes, or significant topography, or where internal and inertial waves or thermohaline effects are important.
DATA
The data discussed here are part of the Acoustic Mid-ocean Dynamics Experiment (AMODE). We deployed six acoustic-transceiver moorings between Bermuda and Puerto Rico (Figure 1) in March 1991, and recovered them one year later. Five moorings were at the vertices of a pentagon inscribed in a circle of radius of 350 km, and the sixth mooring was at the center (25｡?, 66.25｡?).
Circulation maps for the North Atlantic show this region to be well out of the main recirculation near the Gulf Stream, with the possibility of weak (＜5 cm/sec) mean flows wrth poorly determined direction. The topography of the region (taken from ETOPO5) shows smooth variation from about 5400 to 5600m, with stronger gradients outside. This paper will focus on the evolution of anomalies with respect to a range-dependent basic state constructed from the annual average Levitus climatology [Levitus, 1982] for the reion, slightly adjusted by the mean of the anomalies with respect to the climatology for 200 CTD stations taken in June and July around a circle of 500 km radius.
Figure 1 : AMODE region.
