Well organized surface current system appears on the equator (Fig.2). Most of the surface current speed exceeds 2 knots especially in the central part, suggesting the equatorial jet.
2. Zonal section along the equator
Upper layer thermal structure (Fig.3) shows that thermocline is deeper in the east. Temperature of surface mixed layer is 28C and zonal gradient is almost null. However, bathymetric effects can be seen in the vicinity of Maldives (73E). The thermocline raises up abruptly at Maldives and wavy pattern appears at the lee of there. Upper layer salinity section (Fig3) shows strong gradient in the eastern part (85-95E). High salinity cores (>35.6psu; probably originated from Arabian sea) seems to interleave along the bottom of the mixed layer.
Anomaly of dynamic depth for each pressure level (Figure 4) gradually rises to the east for levels 0 to 100db. However, the levels deeper than 100db are almost flat. A small peak appears west of Maldives which is caused by bottom bathymetry.
Vertical section of zonal current component (Figure 4) shows strong eastward current (2-3knots) in the upper layer, and the current extends almost entire area. The highest speed appears in the central part. The thickness of eastward current is generally thin (approximately 1OOm), but comparatively deeper in the east.
3. Meridional section along 64E
Anomaly of dynamic depth for each pressure level (Figure 5) show a moderate peak at the equator for the levels surface to 50db. Down slopes to both hemisphere sides keeps this jet as an geostrophic flow. Consistently, vertical section of zonal current component (Figure 5) shows narrow eastward current band (2-3knots). Its width is estimated to be about 400km, although southern end is uncertain by coalescing with equatorial counter current. Integrating the zonal component of this band, the total transport is about l6sv.
Summary
Zonal wind stress in the observed month was larger than normal (according to JMA). And the equatorial jet was detected clearly in entire observed area. Major observed hydrographic structures are as follows.
1. The observed jet had a length of about 4000km (55-90E) long and a width of 400km at 64E.
2. Surface zonal speed was 2-3knot, and is highest in the central part on the Indian Ocean.
