A Numerical Study on the Coastal Topographic Effect of a Peninsula on the Western Boundary Current

Abstract

Coastal topographic effects of a peninsula on the western boundary current are studied numerically with reference to the difference in northern boundary inclination (NBI) from a zonal direction. It is shown from the numerical experiments that the two dominant path patterns of the western boundary current exist: one flow pattern is a large meander path with spinup and spindown of the cyclonic eddy and the other is a nonlarge (straight) path along the northern boundary. If a peninsula is located upstream (west) of the separation point of the mean flow flowing out from the northernmost area of the western boundary region, a large meander path with spinup and spindown of the cyclonic eddy is changed to an irregular oscillation by the topographic effect of the peninsula in the case of no NBI. A nonlarge meander path with a small cyclonic eddy just downstream of the peninsula is formed in the cases with NBI larger than 10°. Formation of the large meander path and the nonlarge meander path agrees with models without a peninsula and the topographic effect of the peninsula located upstream of the separation point of the mean flow is shown to be relatively small. If a peninsula is located downstream (east) of the separation point of the mean flow, a large meander path has a tendency to appear in the case with a relatively large NBI of more than 20° by the topographic effect of the peninsula, which is different from the previous two cases without a peninsula and with a peninsula located upstream of the separation point of the mean flow. If NBI exceeds 30°, only large meander path is commonly formed in all the cases, and the topographic effect of the peninsula is weak. It is found that both topographic effects of NBI and the peninsula located downstream of the separation of the mean flow are important for path dynamics of a western boundary current.