Tide- and wind-driven variability of water level in Sansha Bay, Fujian, China

Abstract

This study analyzes water-level variability in Sansha Bay and its adjacent waters near Fujian, China, using water-level data observed from seven stations along the coast and wind data observed from a moored buoy near Mazu Island. At super- to near-inertial frequencies, tides dominated the water-level variations, mainly characterized by semi-diurnal (primarily M₂, S₂, and N2) and diurnal tides (primarily K₁, O₁). The correlation coefficients between residual (non-tidal) water-level time series and the observed wind-stress time series exceeded 0.78 at all stations, hinting that the wind acting on the study region was another factor modulating the water-level variability. A cross-wavelet and wavelet-coherence analysis further indicated that (i) the residual water level at each station was more coherent and out-of-phase with the alongshore winds mostly at sub-inertial time scales associated with synoptic weather changes; and (ii) the residual water-level difference between the outer and inner bay was more coherent with the cross-shore winds at discrete narrow frequency bands, with the wind leading by a certain phase. The analysis also implied that the monsoon relaxation period was more favorable for the formation of the land-sea breeze, modulating the residual water-level difference.

Keywords

residual water level / tide / wind / Sansha Bay

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Acknowledgments

This work is supported by the Public Science and Technology Research Funds Projects of Ocean under contract No. 201205009-2, the National Natural Science Foundation of China (Grant Nos. 41276006 and U1405233), and the Open Fund of the Key Laboratory of Ocean Circulation and Waves, Chinese Academy of Sciences under contract No. KLOCAW1408. We thank Professor John Hodgkiss of The University of Hong Kong for assistance with English.

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