ABSTRACT:

The results of inter-comparison study between the Aanderaa RCM 7 and Potok 2M current meters deployed in the Southern Equatorial Indian Ocean during April to September 1996 in phase-II of the INDEX programme has been presented. The vector averages of currents for seven consecutive 10-day ensembles of both Aanderaa and Potok current meters revealed the presence of a meridional flow, with both the Aanderaa and Potok current meters generally showing the identical ensemble averaged northerly /southerly directions. The cross spectral analyses showed that both the current meters were coherent for frequencies < 0.2 cph at 0.01 significance level for both the u and v components of currents. The phase difference between the two types of current meters was nearly zero degree in the above said frequency range indicating that both registered the same signal. At the inertial frequency, rotary spectral analysis showed that the currents are anticlockwise (southern hemisphere) and cross spectral analysis showed that the v component lags behind the u component by 90 degrees.

INTRODUCTION

Three current meter moorings were deployed in the Southern Equatorial Indian Ocean during April to September 1996 in Phase II of INDEX (Indian Deep sea Environment Experiment) programme, which was carried out with Russian collaboration. Two of these three moorings (mooring 1: 10° S, 75° E; total water depth = 6250m; mooring 3: 15° S, 77° E; total water depth = 5210m) had an Aanderaa RCM 7 (Norwegian make) current meter and a Potok 2M (Russian make) current meter at 500 m level. The other current meters (all at levels deeper than 500 m) on the three moorings were of the Potok type. Therefore, in order to confirm the occurrence of meridional flow indicated by the Potok current meters the Aanderaa current meters were included in the second phase.

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