Observational and model studies of the circulation in the Gulf of Tonkin, South China Sea
Beardsley, Robert C.
Viet, Nguyen Trung
MetadataShow full item record
Moored current measurements were made at one mooring site in the northern Gulf of Tonkin for about 1 year during 1988–1989. Analyses were performed to examine characteristics and variability of tidal and subtidal flows. Rotary spectra showed two peaks at diurnal and semidiurnal periods, with higher diurnal energy. Complex demodulations of diurnal and semidiurnal tidal currents indicated that the tidal current magnitudes varied significantly with seasons: more energetic in the stratified summer than in the vertically well-mixed winter. The observed subtidal currents were highly correlated with the surface wind in winter but not in summer; challenging the conceptual summertime anticyclonic circulation pattern derived using wind-driven homogenous circulation theory. The computed currents from a global ocean model were in good agreement with the observed currents. Similar to the current observations, the model-computed flow patterns were consistent with the conceptual wind-driven circulation pattern in winter but opposite in summer. Process-oriented experiments suggest that the summertime cyclonic circulation in the northern Gulf of Tonkin forms as a result of the combination of stratified wind-driven circulation and tidal-rectified inflow from Qiongzhou Strait. The interaction between the southwest monsoon and buoyancy-driven flow from Hong River can significantly intensify the cyclonic circulation near the surface, but its contribution to the vertically averaged flow of the cyclonic circulation is limited.
Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 118 (2013): 6495–6510, doi:10.1002/2013JC009455.
Showing items related by title, author, creator and subject.
Whitehead, John A. (American Meteorological Society, 2009-05)As a driving parameter is slowly altered, thermohaline ocean circulation models show either a smooth evolution of a mode of flow or an abrupt transition of temperature and salinity fields from one mode to another. An abrupt ...
Chechelnitsky, Michael Y. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1999-06)Data assimilation methods, such as the Kalman filter, are routinely used in oceanography. The statistics of the model and measurement errors need to be specified a priori. In this study we address the problem of estimating ...
Zhai, Ping; Pratt, Lawrence J.; Bower, Amy S. (American Meteorological Society, 2015-05)The west-to-east crossover of boundary currents has been seen in mean circulation schemes from several past models of the Red Sea. This study investigates the mechanisms that produce and control the crossover in an idealized, ...