Determination of Tidal Components and Tidal Types Using Harmonic Analysis in the West Sumatera Waters

The tidal of the sea is a phenomenon of rising and falling sea levels periodically caused by the influence of gravity from celestial objects, especially the moon and sun. The purpose of this research is to determine the tidal type in West Sumatra Water, especially in Sabang, Sibolga, and Padang cities. Tidal type can be used as a reference for the port to determine when the ship can go in or out of the port. We used satellite altimetry and tide gauge data. Tidal types in the West Sumatra Waters are influenced by the characteristics of tides in the Andaman Sea and the Indian Ocean. Determining the tidal type required the Formzahl number obtained from the comparison of tidal constants using harmonic analysis. We obtained that the West Sumatra Waters has semidiurnal tidal types with a Formzahl number 0.2013 at Sabang station and has a mixed tidal type (semidiurnal dominant) at Padang and Sibolga stations with Formzahl number values of 0.4306 and 0.4893, respectively. We found 9 tidal components with different amplitudes and phase angles in each component and each station. The tidal components obtained are Z0, M2, S2, K2, K1, 01, P1, M4, and MS4.