Wyrtki(1972) first found the equatorial jet in the Indian Ocean. He showed
velocity field obtained by historical ship drift data in the vicinity of the equator in May and October. The velocity field revealed well organized eastward flow near the equator. He also estimated volume transport of this flow. The jet transports upper layer warm water eastward connecting east/west sector of the tropical Indian Ocean. However, direct measurements of this flow is rare. Fortunately, the authors had a chance to make hydrographic observation along the equator in early November 1995. In this paper, preliminary results of hydrographic structures in the tropical Indian Ocean are shown.
Observation
Japan Fisheries Agency conducted pelagic large squid resources investigation in the Indian Ocean during October 20 1995 through January 8 1996 by using R/V Shoyo Maru (Figure 1). Although the highlights of this investigation were experimental squid jigging and net sampling of squid larvae, also hydrographic sections along the equator (off Sumatra - north of Seychelles) and cross equator along 64E were occupied. CTD (SBE 911plus) casts with 12 Niskin bottles down to 3000m were made each 2 (1) degrees along(across) the equator. Sampled water was used for D.O., salinity, chlorophyl-a, and POM measurements.
Along the ship track, vertical current profile (-700m) were obtained by using ADCP. In this paper, physical properties are mentioned.
Results
1. Sea surface wind and current
On the equator, west or northwest winds were predominant(Fig.2). Systematic westerlies blows in the eastern Indian Ocean, but north component is larger in the western part. According to JMA wind analysis(ODAS), winds on the equator in the month (November) were larger than normal and were the largest among the past five
