Seasonal Variations of the Coastal Currents and Eddies in the Persian Gulf: A Numerical Case Study

Abstract

AbstractThis study employed a three-dimensional hydrodynamic model (COHERENS) to investigate the seasonal cycles of the mesoscale currents and eddies in the Persian Gulf with a 2-min horizontal resolution. The barotropic time step of 20 s and the baroclinic time step of 600 s were selected. In a vertical coordinate system with a vertical sigma array, there are equal numbers of vertical columns of water at each depth of the water volume. In this case, we considered 10 vertical sigma layers. We obtained a climatic stability during a 10-year run of the model. The simulation showed a coastal jet stream with a speed rate of 30 cm/s from May to October. The coastal jet stream in the vicinity of the Iranian coast is limited only to the surface as it flows southeastward and the counter current flows with a northwestern direction. However, this jet stream appears over the column of the water from the surface to the seafloor and flows southeastward along the Arabian coasts. Simulation results showed three cyclonic eddies with a diameter of about 100 km in September, the maximum speeds of which are observed at their north part. Decomposed eddies filled the entire water column. Additionally, at the end of summer when the eddy was well developed, the maximum vorticity was observed. The results revealed that anticyclonic eddy depths were higher than the depths of the cyclonic type, which is related to the extent of the eddy's development into the seabed and the effects of baroclinic instability on the water column.