A NUMERICAL STUDY OF CURRENTS, HEAT ADVECTION, AND SEA-LEVEL FLUCTUATIONS IN THE YELLOW SEA IN WINTER 1986

A vertically integrated model that incorporates horizontal temperature variations is used to study the circulation of the Yellow Sea in a wi ntertime period for which velocity and temperature measurements are av ailable at several moorings locations along a central trough. The mode l features realistic bottom topography and is forced with wind stress and heat flux fields from 13 January to 22 February 1986. The model al so incorporates, as a boundary condition, sea-level fluctuations deriv ed from coastal and insular ride gauge stations along model boundaries in open waters. The model reproduces well sea level fluctuations alon g the coasts of both China and Korea. The hindcast velocity time serie s, particularly for the north-south component, track those obtained fr om direct measurements at the moorings. The model momentum balance ind icates that the northward flow in the trough is driven by a sea level setup to the south in response to northerly wind bursts in the winter monsoon. The sea-level fluctuations propagate around the Yellow Sea em bayment in a counterclockwise sense and exhibit a northward increase i n amplitude along both the China and Korea coasts, apparently due to t he general shallowness of the northern reaches of the embayment. The l ack of a suitable initial condition in temperature and the presence of large biases in the sea surface heat flux distribution preclude the h indcast of the temperature field. Yet trajectories of model fluid disp lacement confirm an overall northward transport of mass, and hence hea t and salt, even though the northerly wind-pulse-dominated current flu ctuates with a small mean. While wintertime currents in the Yellow Sea appear dominated by the wind forcing, empirical orthogonal function a nalysis of model sea-level fluctuations attributes 48% of the variance to a mode whose time variation follows those of sea-level heights imp osed along the open model boundaries. The mode with a time variation s imilar to that found in the wind stress magnitude time series accounts for only 28% of the variance. This suggests the domination of sea-lev el fluctuations by low-frequency fluctuations in the Kuroshio.