2007 Volume 16 Issue 3 Pages 203-221
A long term, continuous current observation with bottom-mounted ADCP was conducted to elucidate the residual current field over the head of Ariake Bay. The residual current component was extracted from the observed data, and a multiple linear regression analysis was applied to specify the cause of variation of the upper layer residual current. In the analysis, tide, river inflow and wind were taken as independent variables. The result was tested by a numerical model. In addition, the fluctuation in the residual current over the head of Ariake Bay was examined. It was shown that the M2 major and minor axes components of the upper layer residual current off Tara town during winter were mainly dominated by the influence of tide and wind, respectively. It was also shown that the residual current off Konagai town was modified mainly by wind during the stratified season and by tide during the unstratified season.
The model also resolves how variation in the residual current field over the head of the bay is induced by variations in tide, river inflow and wind. In the spring tidal phase, the horizontal circulation pattern corresponding to the topography was predominant, while in the neap tidal phase the estuarine circulation pattern was predominant. The influence of river flow on the residual current field was shown only in the stratified season, while the influence of the wind was dependent on the season. It was not only due to changes in the wind, but also to the change in response characteristics. Thus, even if the fluctuation of the wind was the same throughout the season, the fluctuation in the residual current was not the same.
