Propagation characteristics of near-inertial waves along the continental shelf in the wake of the 2008 Typhoon Hagupit in the northern South China Sea (original) (raw)
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Poleward Propagation of Typhoon-Induced Near-Inertial Waves in the Northern South China Sea
Frontiers in Marine Science, 2021
One of the main responses of the ocean to typhoons is the generation of near-inertial waves (NIWs), whose intrinsic frequency is close to the local inertial frequency. Based on the mooring observations, we carefully investigated the spatial–temporal variations in NIWs in the northern South China Sea (SCS) after Typhoon “Haima,” which passed through the northern SCS from October 20 to 21, 2016, with its track parallel to the mooring array on its northeast side. Moorings in different locations responded differently to this typhoon, with stronger NIWs found on the continental slope to the shelf break and relatively weak NIWs found on the shallow continental shelf. Strong NIWs appeared twice within a short period and showed different characteristics and frequencies. The first NIWs were generated locally with blue-shifted (super-inertial) frequencies. These initial NIWs were dominated by the first three baroclinic modes and rapidly weakened due to their propagation away and local dissipa...
Upper ocean near-inertial response to 1998 Typhoon Faith in the South China Sea
Acta Oceanologica Sinica, 2012
During the South China Sea monsoon experiment (SCSMEX), three autonomous temperature line acquisition system (ATLAS) buoys with acoustic Doppler current profiler (ADCP) were moored in the South China Sea to measure temperature, salinity and current velocity. Typhoon Faith passed through about 250 km south to one of the mooring buoys located at 12 • 58.5 N, 114 • 24.5 E from December 11 to 14, 1998. The data analysis indicates that the typhoon winds induce a great increase in the kinetic energy at near-inertial frequencies with two maxima in the mixed layer and thermocline. The near-inertial oscillations were observed at the upper 270 m in the wake of Typhoon Faith. The oscillations were originally excited in the sea surface layer and propagated downward. The amplitudes of the oscillations decrease with depth except in the thermocline. The near-inertial oscillation signals are also remarkable in temperature and salinity fields.
Impact of Wave-Ocean Interaction on Typhoon Hai-Tang in 2005
SOLA, 2010
We investigated the impact of wave-ocean interaction on numerical predictions for Typhoon Hai-Tang in 2005 using a nonhydrostatic atmosphere model coupled with a third-generation ocean wave model and a mixed-layer ocean model. Here we address the effect of breaking surface waves on entrainment induced at the mixed-layer base, assuming that the turbulent transport due to breaking surface waves is expressed as a function of both waveinduced and surface wind stresses. The introduction of breaking surface waves into the coupled model enables us to reproduce the evolution of Hai-Tang's central pressure and sea-surface temperature (SST) distribution more realistically. SST decreases significantly (rarely) along Hai-Tang's track where the mixed-layer depth is relatively shallow (deep). Hai-Tang tends to intensify where the initial mixed layer is relatively deep along Hai-Tang's track. Introducing the wave-ocean interaction may lead to more precise tropical cyclone intensity prediction through more realistic reproduction of the SST distribution.
Observations of strong near-bottom current after the passage of Typhoon Pabuk in the South China Sea
Journal of Marine Systems, 2011
The vertical structure of current field in the northern South China Sea affected by the passage of Typhoon Pabuk is investigated using the observational data. The strong near-bottom current which has a duration of less than 1 day is observed twice whereas such a current is almost missing at some intermediate layers. It is suggested by the power spectral density that the typhoon strengthens the near-inertial current which is the most significant in the upper layer and the weakest in the middle layer after the passage of Pabuk. The wavenumber rotary spectrum is calculated to study the characteristics of the energy which the typhoon injects into the ocean, and it is suggested that the strong near-bottom current may be supported by the transport of energy by the near-inertial waves induced by typhoon, thus the pressure gradients might be established through the continental slope and induce the strong near-bottom current.
Continental Shelf Research, 2016
This study deals with winter storm-induced continental shelf waves (CSWs) in the northern South China Sea in winter 2009 using tidal gauge data and along-track satellite altimeter data. The results show that the periods of CSWs propagating along the coast from Kanmen to Shuidong are in bands of 62 and 133 h. The phase speeds are in a range from 8 to 13 m s-1 between Kanmen and Shantou, from 9 to 11 m s-1 between Shantou and Huizhou and from 10 to 15 m s-1 between Huizhou and Shuidong, respectively. Satellite altimeter captured along-track sea level anomaly during the CSW events. Further analysis using the theoretical cross-shore CSW modes to fit the along-track sea level anomaly data indicates that the first three wave modes play important roles during the CSW events and the first mode is a dominant component.
Typhoon Effects on the South China Sea Wave Characteristics During Winter Monsoon
2006
Ocean wave characteristics in the western Atlantic Ocean (Hurricane Region) to tropical cyclones have been well identified, but not the regional seas in the western Pacific, e.g., the South China Sea (Typhoon Region). This is due to the lack of observational and modeling studies in the regional seas of the western Pacific. To fill this gap, Wavewatch-III (WW3) is used to study the response of the South China Sea (SCS) to Typhoon Muifa (2004). The major purposes are to find the similarity and dissimilarity of wave characteristics between the two regions, and to evaluate the WW3 capability to typhoon forcing. The WW3 model is integrated from the JONSWAP wave spectra with a tropical cyclone wind profile model, simulating Typhoon Muifa, from 16 to 25 November 2004. This study shows strong similarities in the responses between Hurricane and Typhoon Regions, including strong asymmetry in the significant wave height (H s) along the typhoon translation track with the maximum H s in the right-front quadrant of the typhoon center, and asymmetry in the directional wave spectra at different locations (frontward, backward, rightward, and leftward) around the typhoon center. The unique features of the SCS wave characteristics to Muifa are also discussed.
Progress in Natural Science, 2008
The WAVEWATCH-III wave model is implemented in the South China Sea to investigate the air-sea momentum flux in high wind conditions during 23 passages of typhoon occurred in 2005. The wave model is driven by the reanalyzed surface winds assimilated by several meteorologic data sources. The friction velocity was calculated and the relationships between different air-sea momentum parameters were studied. The results show that the drag coefficient decreases with the wave age generally and levels off for wind speeds higher than 35 m/s under typhoon wind forcing. The spatial variations of air-sea momentum flux parameters in high wind conditions forced by typhoons are completely different from those at weak wind speeds and significantly depend on the relative position from the typhoon center.
Typhoon-induced ocean responses off the southwest coast of Taiwan
Ocean Dynamics, 2014
ABSTRACT Typhoons can cause substantial sea surface cooling (typically 2–4 °C), which is usually biased to the right side of the storm track. Under influence of the complex bathymetry of the southern Taiwan Strait (TS), two types of sea surface temperature (SST) response, cooling and warming, each associated with a different type of typhoon track were identified using satellite and mooring observations. When a typhoon moved westward (or northwestward) and passed through the TS (track A), the SST cooling in the TS was biased toward the left of the storm track. Numerical model results indicated that in track A, strong wind stress accelerates the flow east of the Taiwan Banks and drove the bottom flow to uplift due to the topography. Moreover, both wind stress and wind stress curl enhanced the Luzon loop. After the typhoon passed, the mean circulation was modified around strong cooling in the southern TS, causing more South China Sea surface water to be distributed to the Kuroshio region. However, when a typhoon moved westward (or northwestward) and passed south of the TS, SST warming was induced in the southern TS (track B). The model results indicated that when the typhoon passed to the south of the TS, the typhoon-induced horizontal divergent flow travelled to the north, where it encountered the shallower shelf of the TS that was confined to the water, causing warm water transported into this area to accumulate and downwelling to occur. This can be regarded as redistributing the heat content in the shelf area. After the typhoon, the thickened mixed layer resulting from downwelling prevented the formation of near-inertial waves and reduced the vertical mixing.
NONLINEAR INTERNAL WAVE STUDY IN THE SOUTH CHINA SEA
Advances in Engineering Mechanics - Reflections and Outlooks - In Honor of Theodore Y.-T. Wu, 2005
The internal wave distribution map in the northeast part of South China Sea (SCS) has been compiled from hundreds of ERS-1/2, RADARSAT and Space Shuttle Synthetic Aperture Radar (SAR) images. Based on the map compiled from satellite data, the wave crest can be as long as 200 km with amplitude of 100 m. In recent Asian Seas International Acoustics Experiment (ASIAEX), extensive moorings have been deployed around the continental shelf break area in the northeast of South China Sea. Simultaneous RADARSAT SAR images have been collected during the field test to integrate with the in-situ measurements from moorings, ship-board sensors, and CTD casts. Besides it provides synoptic information, satellite imagery is very useful for tracking the internal waves, and locating surface fronts and mesoscale features. Environmental parameters have been calculated based on extensive CTD casts data near the ASIAEX area. Nonlinear internal wave models have been applied to integrate and assimilate both SAR and mooring data. The shoaling, turning, and dissipation of large internal waves on the shelf break, elevation solitons, and wave-wave interaction have been studied.