Tidal characteristics in the Gulf of Khambhat, northern Arabian Sea – based on observation and global tidal model data

Abstract

Summary Tidal characteristics of the Gulf of Khambhat are described based on measured and modelled sea-level data. Data were recorded at three locations inside and two locations outside the Gulf with record lengths of 6–12 months to study the tidal propagation. A northward increase in tidal amplitude is noticed from Daman (eastern side) and Diu (western side) and attains maxima at Bhavnagar. A similar trend is followed by the amplitude of the major tidal constituents, although there are discrepancies for that of the minor constituents. The non-tidal factor which influences the sea-level is the local wind, especially the alongshore component of wind. A positive correlation is obtained between the sea-level and the meridional component of wind at each location. Harmonic analysis of sea-level data shows that M2 is the major tidal constituent which propagates in a non-linear fashion inside the Gulf. Tides from two global tide models (MIKE21 and FES2014) have been compared with the measured data, which could be used for further prediction of the tides and sediment transport in the Gulf. The tide elevation derived from the MIKE21 model has further been used for the harmonic analysis of tide. The tides predicted using one-month data are up to 10% smaller than those predicted using the one-year data. The global tide model FES2014 data performs well with measured data for offshore locations, whereas it fails to predict the same for the inner Gulf locations. The study manifests the fact that to understand the dynamics of complex tidal areas, regional models should better be used than global tidal models.