Evidence for a counter-wind current in winter off the southeast coast of China

Abstract

Regarding the current pattern in winter in the near-sea region of Zhejiang, Fujian and Guangdong (including the western and central parts of the Taiwan Strait), oceanographers both at home and abroad had considered unanimously that under the intense influence of the northerly monsoon, the current (not only at the surface but also in the deep and near-bottom layers) flows southwestward with the wind. It was not until the end of the fifties that scientists began to question such a traditional concept.

In this paper, based on the results of more than 20 years’ studies on the current patterns of the East China and South China Seas, all kinds of current data available are reanalysed comprehensively. These data include: 1) current measurements at day-night anchored stations, and with mooring buoys, collected mostly from 1959 to 1982 by many Chinese oceanographic and fisheries organizations; 2) current vectors derived from the ship-drift of Japanese naval vessels in the period from 1910 to 1921; and 3) geostrophic current velocities deduced from hydrographic observations in the periods of the CSK and 1975–1976 conducted by the Fisheries Research Station, Hong Kong, and the SOA. A combination of all the evidences revealed in the above data suggests and confirms that, besides the China Coastal Current flowing southwestward at a shallow layer of a zone closely adjacent to the coast, there also exists a northeastward counter-wind current in winter off the southeast coast of China (though its surface current may be weakened or even covered up by the drift current when the northerly monsoon strengthens). Furthermore, the two parts of the winter counter-wind current in the South China Sea and the East China Sea are connected through the Taiwan Strait. This suggestion now has been confirmed by the recent observations in the Taiwan Strait, i.e., 1) with sea-bed drifters released in 1984 (Zhang, 1985) and 2) with current meter moorings deployed in 1983 (Chuang, 1985).

It is suggested that detailed field investigation in winter for filling the gap of observations should be needed to give further confirmation of this important new finding. At the same time, dynamical, numerical and experimental studies should also be carried out for a better understanding of the mechanism of this counter-wind current, and its variations and correlation with the adjacent currents, such as the southward flowing coastal current and the northward flowing Kuroshio Branch.