Semi-Annual Variability In The Observed And OGCM Simulated Zonal Currents In The Equatorial Indian Ocean

ABSTRACT Analysis of time series of currents measured along the equator at 77E 83E and 93E locations is presented with an emphasis on the semi-annual variability of zonal currents in the Eastern equatorial Indian Ocean EEIO during November 2004 July 2006. The observed currents are compared with the Ocean General Circulation Model OGCM simulated currents for the study period. Semi-annual Wave SAW harmonic is fitted to the Acoustic Doppler Current Profiler ADCP measured currents at each depth at 8m depth bins in the upper 200m time series of zonal velocity revealed i predominant semi-annual equatorial jets in spring April-May and fall September October with velocity ranging between 120 and 160 cms at 77E and 83E and weaker jets at 93E with inter-annual variability and ii eastward flowing spring and monsoon Equatorial Undercurrents EUC at around 80-100 m depth. The amplitude of the SAW is large 57 cms at 77E and small 13 cms at 93E. The Observed variation of zonal velocity is compared well with the model simulations at 77E and 83E but deviated at 93E.