Seasonal Circulation of Gulf of Khambhat, India using High Frequency Radars

The present work analyzed the high frequency radar-derived surface current data for seasonal variation of tidal and non-tidal currents in the Gulf of Khambhat, India during 2018. The analysis showed that the M2 tidal (time period 12.42 hours) current is the strongest tidal constituent of magnitude from 1.0 m/s to 1.5 m/s in different seasons. This M2 currents is more than three times higher than the K1 (time period 23.93 hours) tidal current, which varies from 0.2 to 0.5 m/s. The meridional component than the zonal majorly drives the total currents. The de-tided surface currents is much less than the tidal current. The percentages of the tidal current to the total current is around 80%. The inclination of the tidal ellipse varies between 60 degrees - 70 degrees in different seasons, indicate the direction of tidal flow. A convergence (divergence) of surface currents is noted during flood and ebb currents around 21 degrees N due to downslope on both the sides. In February 2018, a strong surface current with a magnitude of around 0.5 m/s was seen flowing from the Arabian sea to the Gulf on the western and southern Gulf. A flow with 0.1 to 0.3 m/s is noted on the eastern Gulf from the shallower bathymetry to deep regions near the Tapti River. A cyclonic circulation flow in noted in August. A time-series analysis of the daily currents showed that oscillations of 5-, 10-, 15-days exist in the current observation. This study also highlighted the need of subsurface ocean observation for studying the ocean dynamics in the Gulf.