SURFACE CIRCULATION OFF SOMALIA AND WESTERN EQUATORIAL INDIAN-OCEAN DURING SUMMER MONSOON OF 1988 FROM GEOSAT ALTIMETER DATA

The sea level variability derived from repeating tracks of the Geosat altimeter data during the late phase (August-September) of the summer monsoon of 1988 revealed the presence of multiple meso-scale eddy feat ures with clockwise and anti-clockwise rotation. During August, the pr ime eddy or the Great Whirl centred at 9.5 degrees N, 53.5 degrees E o ff northern Somalia and the southern gyre centred at 3 degrees N, 51.5 degrees E off southern Somalia, both are clearly identified with cloc kwise rotation. The region of lower sea levels off the central Somalia coast (between 6 degrees N and 9 degrees N) coincides with the cold w ater wedge formed by the offshore movement of the cold upwelled waters from the Somalia coast during the summer monsoon. By September the so uthern gyre weakens, while the prime eddy persists. The surface circul ation is characterized by nearly meridional flows in the equatorial re gion. A strong narrow (similar to 100 km) southward jet-like flow is n oticed south of 7 degrees N between 53 degrees and 54 degrees E during September. In general, these circulation features are in agreement wi th the sea surface topography derived from the hydrographic data colle cted in this region during the same period on board the ORV Sagar Kany a.