Search

This study is the first to depict typhoon-induced continental shelf wave (CSW) propagation in the eastern Taiwan Strait (TWS) during the passage of Typhoon Meranti in 2016 using tidal gauge data and along-track satellite altimeter data. The strong amplitude response of sea level oscillations (within the range of 0.30–0.54 m) as a free, barotropic CSW after Meranti, which impacted the TWS, was clearly detected in time and frequency (in bands of 64–81 h) using wavelet and cross-wavelet analyses. The measured group and phase speeds were consistent with the dispersion curves for CSW with the first-mode derived from the cross-shelf sections of the eastern TWS, with the mean speeds reaching 3 and 5.6±0.7 m/s, respectively. Coincidentally, the typhoon-induced sea level anomaly (SLA) was also captured by the satellite altimeter before this CSW entered into the TWS. Using the theoretical cross-shore CSW modes to fit the SLA data, the results indicated that the first three wave modes can interpret this CSW event appeared in the southern TWS very well, with the first mode being the dominant one. [ABSTRACT FROM AUTHOR]

In situ hydrographic and current observations from cruises in 1998 and 1999, together with 20-year (1993–2012) sea level anomaly (SLA) data from satellite altermeter, have been used to study the vertical structure, seasonal development, and interannual variability of the anticyclonic circulation in the southern South China Sea (SCS). The relationship between the anticyclonic circulation and its northern flanking cyclonic eddy are described. Three associated circulation patterns are identified. The anticyclonic circulation is present for an average of 108 ± 30 days per year, while its northern flanking cyclonic eddy is present for an average of 54 ± 25 days per year. The intraseasonal variability of the anticyclonic circulation is intense as a result of advection with the flanking northern cyclone, which accompanies the gyre on average about 60% of the time. The vertical structure of the anticyclonic circulation in 1998 (1999) penetrated much deeper, and its horizontal scope became wider in June (July) than in April. The anticyclonic circulation shows some difference between 1998 and 1999, displaying earlier appearance, more northward position, and non-dipole pattern in 1998, suggesting that the interannual variability of the anticyclonic circulation is related to El Niño Southern Oscillation (ENSO) events. The effect of Sverdrup balance via westward propagating Rossby wave on the seasonal development of the anticyclonic circulation has been discussed. [ABSTRACT FROM AUTHOR]

11-year satellite altimeter sea surface height (SSH) anomaly data from January 1993 to December 2003 are used to present the dominant spatial patterns and temporal variations of the South China Sea (SCS) surface circulation through Empirical Orthogonal Function (EOF) analysis. The first three EOF modes show the obvious seasonal variations of SSH in the SCS. EOF mode one is generally characterized by a basin-wide circulation. Mode two describes the double-cell basin scale circulation structure. The two cells were located off west of the Luzon Island and southeast of Vietnam, respectively. EOF mode three presents the mesoscale eddy structure in the western SCS, which develops into a strong cyclonic eddy rapidly from July to September. EOF mode one and mode three are also embedded with interannual signals, indicating that the SCS surface circulation variation is influenced by El Niño events prominently. The strong El Niño of 1997/98 obviously changed the SCS circulation structure. This study also shows that there existed a series of mesoscale eddies in the western SCS, and their temporal variation indicates intra-seasonal and interannual signals. [ABSTRACT FROM AUTHOR]