Coastally Trapped Long Waves in the Yellow Sea

Abstract

The coastally trapped long-wave theory is adapted to a double shelf bottom topography in the development of a barotropic long-wave model for calculating wintertime wind-driven currents and sea level fluctuations in the Yellow Sea. The low frequency, free wave solutions consist of two infinite sets of modes, one set trapped to each side of the trough that separates the two plane shelves. The phase propagation of either set of waves depends upon the slopes of both shelves. Forced wave motions are considered for geostrophic winds calculated at 35°N, 125°E for the period of January?April 1986 for which point measurements of currents and sea level fluctuations are available. Comparison to these measurements shows that the model reproduces reasonably well upwind flow events in the trough that dominate the wind-driven wintertime regime. The anatomy of a typical event of this type shows that the Korea-side Kelvin wave is mainly responsible for the establishment of the downwind setup in sea level and in the ultimate generation of an adjustment drift to the right of the wind necessary for the initiation of the upwind flow. The qualitative similarity found between the model output in alongshore velocity and the observation in coastal waters of Korea, in which no clearly dominant features exist, suggest the importance of the influence of wave modes trapped on one shelf in the determination of motions on the other.