Application of S_TIDE in exploration of seasonal variations of internal tidal amplitudes in the northern South China Sea

View More View Less
  • 1 1 College of Ocean Science and Engineering, Shandong University of Science and Technology, Qingdao, 266590, China.
  • | 2 2 Laboratory of Marine Science and Numerical Modeling, First Institute of Oceanography, Ministry of Natural Resources, Qingdao, 266061, China.
  • | 3 3 Laboratory for Regional Oceanography and Numerical Modeling, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, 266237, China.
  • | 4 4 Qingdao Campus of Naval Aviation University, Qingdao, 266021, China.
  • | 5 5 Key Laboratory of Physical Oceanography, Qingdao Collaborative Innovation Center of Marine Science and Technology, Ocean University of China, Qingdao, 266021, China.
  • | 6 6 Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China.
© Get Permissions Rent on DeepDyve
Restricted access

Abstract

An enhanced harmonic analysis (S_TIDE) approach is adopted to examine the seasonal variations of internal tidal amplitudes in the northern South China Sea (SCS). Results of idealized experiments reveal that the seasonality can be captured by S_TIDE. By applying S_TIDE to mooring data, observed seasonality of internal tidal amplitudes in the northern SCS are explored. Not diurnal and semidiurnal internal tides (ITs), but overtides and long-period constituents of ITs exhibit clear seasonal cycles. However, differences between amplitudes of the eastward velocity and the northward counterpart are evident for K1, M2 and MK3, which may be caused by the intensification of background currents. Amplitudes of those ITs are stronger at intersection time between spring and summer in the eastward direction, but weaker in the northward direction. EOF analysis reveals that modes of diurnal ITs are higher than those of seimidiurnal ITs, which induces relatively more complicated seasonal variations. In addition to intensification of background currents, influences of surface tides and stratification will also induce variations of internal tidal amplitudes, introducing tremendous difficulty in predicting variation trends of internal tidal amplitudes, which greatly reduces predictability of ITs.

Corresponding authors: ZEXUN WEI (weizx@fio.org.cn) and XIANQING LV (xqinglv@ouc.edu.cn)

Abstract

An enhanced harmonic analysis (S_TIDE) approach is adopted to examine the seasonal variations of internal tidal amplitudes in the northern South China Sea (SCS). Results of idealized experiments reveal that the seasonality can be captured by S_TIDE. By applying S_TIDE to mooring data, observed seasonality of internal tidal amplitudes in the northern SCS are explored. Not diurnal and semidiurnal internal tides (ITs), but overtides and long-period constituents of ITs exhibit clear seasonal cycles. However, differences between amplitudes of the eastward velocity and the northward counterpart are evident for K1, M2 and MK3, which may be caused by the intensification of background currents. Amplitudes of those ITs are stronger at intersection time between spring and summer in the eastward direction, but weaker in the northward direction. EOF analysis reveals that modes of diurnal ITs are higher than those of seimidiurnal ITs, which induces relatively more complicated seasonal variations. In addition to intensification of background currents, influences of surface tides and stratification will also induce variations of internal tidal amplitudes, introducing tremendous difficulty in predicting variation trends of internal tidal amplitudes, which greatly reduces predictability of ITs.

Corresponding authors: ZEXUN WEI (weizx@fio.org.cn) and XIANQING LV (xqinglv@ouc.edu.cn)
Save