Model-simulated coastal trapped waves stimulated by typhoon in northwestern South China Sea
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In this paper, we apply an unstructured grid coastal ocean model to simulate variations in the sea level and currents forced by two typhoons in the northwestern South China Sea (SCS). The model simulations show distinct differences for the two cases in which the typhoon paths were north and south of the Qiongzhou (QZ) Strait. In both cases, coastal trapped waves (CTWs) are stimulated but their propagation behaviors differ. Model sensitivity simulations suggest the dominant role played by alongshore wind in the eastern SCS (near Shanwei) and southeast of Hainan Island. We also examine the influence of the Leizhou Peninsula by changing the coastline in simulation experiments. Based on our results, we can draw the following conclusions: 1) The CTWs stimulated by the northern typhoon are stronger than the southern CTW. 2) In the two cases, the directions of the current structures of the QZ cross-transect are reversed. The strongest flow cores are both located in the middle-upper area of the strait and the results of our empirical orthogonal function analysis show that the vertical structure is highly barotropic. 3) The simulated CTWs divide into two branches in the QZ Strait for the northern typhoon, and an island trapped wave (ITW) around Hainan Island for the southern typhoon. 4) The Leizhou Peninsula plays a significant role in the distribution of the kinetic energy flux between the two CTW branches. In the presence of the Leizhou Peninsula, the QZ branch has only 39.7 percent of the total energy, whereas that ratio increases to 72.2 percent in its absence.
Key wordscoastal trapped waves typhoon surge coastline influence South China Sea ocean modeling
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The datasets for this study are available from the following sources: 1) Tidal gauge data from the University of Hawaii Sea Level Center; 2) Wind data from the Physical Oceanography Distributed Active Archive Center; 3) Air pressure data from the NOAA-CIRES Climate Diagnostics Center; 4) Topography data ETOP1 (bed-rock) from the National Centers for Environmental Information; 5) Temperature and salinity data from the Simple Ocean Data Assimilation/TAMU Research Group; and 6) Typhoon track data from the Joint Typhoon Warning Centre for western pacific ocean.
We thank the National Natural Science Foundation of China (Nos. 41266002, 41406031, 41406044), the Special Fund for Basic Scientific Research Business of Central Public Research Institutes (No. 2015P02), and the Fund of Key Laboratory of Global Change and Marine- Atmospheric Chemistry, SOA (No. GCMAC1308) for their support.
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