Mooring observed mode-2 internal solitary waves in the northern South China Sea
- PDF / 2,791,996 Bytes
- 8 Pages / 595 x 842 pts (A4) Page_size
- 83 Downloads / 183 Views
Mooring observed mode-2 internal solitary waves in the northern South China Sea Liang Chen1, 2, 3*, Xuejun Xiong1, 2, 3*, Quanan Zheng4, Yeli Yuan1, 2, 3, Long Yu1, 2, 3, Yanliang Guo1, 2, 3, Guangbing Yang1, 2, 3, Xia Ju1, 2, 3, Jia Sun1, 2, 3, Zhenli Hui1, 2, 3 1 First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China 2 Founctional Laboratory for Regional Oceanography and Numerical Modeling, Pilot National Laboratory for Marine
Science and Technology (Qingdao), Qingdao 266237, China 3 Laboratory for Regional Oceanography and Numerical Modeling, Pilot National Laboratory for Marine Science and
Technology (Qingdao), Qingdao 266237, China 4 Department of Atmospheric and Oceanic Science, University of Maryland, College Park, Maryland 20742, USA
Received 20 January 2020; accepted 5 May 2020 © Chinese Society for Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract
The mode-2 internal solitary waves (ISWs) generated by mode-2 internal tide (IT) are identified by mooring observations in the northern South China Sea (SCS) from 2016 to 2017. Two mode-2 ISWs with a re-appearance period of 24.9 h observed on 29 and 30 July 2016 are characterized by type-b ISWs. They occurred when the isotherms compressed obviously in the vertical direction. Modal decomposition of IT horizontal currents shows that the vertical compression of the isotherms is mainly caused by diurnal mode-2 IT. The analysis of the role of the density stratification reveals that a deeper and thinner pycnocline is favorable for generation of mode-2 ISWs rather than pycnocline intensity. By comparing the mode-2 nonlinear, dispersion coefficients and the Ursell numbers calculated based on the stratification associated with different kinds of ITs with the observation results, it is shown that the diurnal mode-2 IT plays a crucial role in the generation of the mode-2 ISWs. When the diurnal mode-2 IT interacts with the semidiurnal IT and causes a deeper and thinner pycnocline, the mode-2 ISWs are easily excited. Key words: mode-2 internal solitary waves, South China Sea, internal tide, mooring observation Citation: Chen Liang, Xiong Xuejun, Zheng Quanan, Yuan Yeli, Yu Long, Guo Yanliang, Yang Guangbing, Ju Xia, Sun Jia, Hui Zhenli. 2020. Mooring observed mode-2 internal solitary waves in the northern South China Sea. Acta Oceanologica Sinica, doi: 10.1007/s13131-0201667-0
1 Introduction Previous investigations have shown that the internal solitary waves (ISWs), with large amplitudes and strong current velocities, are broadly distributed in the stratified coastal ocean and marginal seas (Jackson, 2007; Zhao et al., 2006; Stanton and Ostrovsk, 1998; Apel et al., 1985; Osborne and Burch, 1980). The South China Sea (SCS), in particular the northern SCS, is one of ocean areas where the energetic ISWs occur frequently (Wang et al., 2013; Zheng, 2017; Chen et al., 2018). In terms of the wave modes, the observed ISWs in the northern SCS could be categorized as two types, i.e., the first baroclinic mode (mo
Data Loading...
