Observations of strong near-bottom current after the passage of Typhoon Pabuk in the South China Sea (original) (raw)
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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.
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...
Bulletin of Marine Science, 2018
A mooring and a real-time buoy allowed observation of oceanic and atmospheric variation in the wake of the 2008 Typhoon Hagupit in the South China Sea (SCS). In the present study, a regional ocean modeling system (ROMS) was used to explore the propagation characteristics of near-inertial waves (NIWs) along the continental shelf. The simulated NIWs were similar to the observation results. There were strong NIWs after the passage of Typhoon Hagupit, and the NIWs presented dual peaks, with one located in the mixed layer and the other at the thermocline. In the upper layer, the near-inertial kinetic energy on the left of the typhoon track was slightly weaker than that on the right. The responses of the ocean to the typhoon in shallow (<100 m) vs deep (>200 m) areas were different. The thermocline was significantly enhanced and deepened in shallow areas. The near-inertial kinetic energy of the thermocline in shallow areas occurred earlier and more intensely than that in the deep areas. The shallower mixed layer and the stronger thermocline in shallow areas are the main reasons for the difference in response. When the typhoon arrived, the mixed layer in shallow areas sank rapidly, causing the thermocline to sink, and the thermocline strength to increase and the thickness to decrease. The thermocline triggered NIWs during its compression. High compression and a strong thermocline result in powerful NIWs.
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.
Modeling typhoon wind power spectra near sea surface based on measurements in the South China sea
Journal of Wind Engineering and Industrial Aerodynamics, 2012
This study focuses on enhancing our understanding of the spectral features of typhoon winds with critical implications on the mitigation of disproportionate damage experienced in typhoons-prone coastal regions. Examination of data suggests that generally used empirical models of wind power spectrum for extratropical storms may not adequately represent the tropical cyclone winds. In this paper, a data-driven model is proposed for wind power spectrum in tropical cyclone winds over the sea surface. Rather than fitting data to a universal spectral description, first the physical meaning of parameters in such a model is carefully examined and the contribution of each parameter is delineated. With these backgrounds, field measurements in typhoon Hagupit are used to model these spectral parameters in terms of the Monin-Obukhov length, mean wind speed and roughness length. Finally, the proposed spectral model is validated using arbitrarily selected four hours of data in different sectors of typhoon Hagupit wind field. The model shows a good agreement with the measurements. (A. Kareem), llsong@grmc.gov.cn (L. Song), qinpeng@grmc.gov.cn (P. Qin).
Swell Source Analysis of East China Sea Under the Influence of Typical Typhoon Scenarios
China Ocean Engineering
The characteristics of swells within the East China Sea have been reported by Tao et al. (2017), while the question of where the swells come from remains unanswered. By using the wave model WAVEWATCH III and the swell tracking method proposed by Hanson (2001), the spatial sources of the swells are investigated during four typical typhoon scenarios, which usually affect the wave environment in the East China Sea, including the Recurving type, the Northward type, the Westward type (striking the East China Sea) and the Westward type (over the South China Sea). The numerical results show that parts of the swells are from the North West Pacific with a long-distance travelling. The moving paths of the swells are affected by the typhoon tracks, which result in various fetches. The Westward type (over the South China Sea) makes one peak in the evolution process. The landing process of the Westward type (striking the East China Sea) could result in swells with low energy. The swell energy depends on swell propagation distance, existence time and wind intensity of generation fetch. The consistent fetch and forceful wind intensity make swell carry more energy.
Typhoon activity and some important parameters in the South China Sea
Weather and Climate Extremes, 2017
This study aims to statistically describe temporal and spatial variations of sea surface temperature (SST), latent heat flux (LHF), sensible heat flux (SHF), and precipitation rate with typhoon activity over the South China Sea. The correlations of the parameters and their connections with the physical phenomena are clearly presented. This is fundamental to predict a typhoon's intensity and track. The effects were investigated from 1991 to 2011 based on archived data from the National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP-NCAR) and the number of typhoons were sourced from the International Best Track Archive for Climate Stewardship (IBTrACS). The results showed that most typhoons occurred in August and September, which was related to high temperature in the summer season and the southwest monsoon in the area. The maximum mean values of SST in May and June were related to the East Asian Monsoon. The average values of LHF were highest in July, and the mean values of SHF were highest in July and August. SHF varied gradually at different months compared with LHF. In addition, the average of precipitation rate was highest in November, which can be related to the northeasterly winter monsoon. The relationships of the aforementioned parameters were obtained using Pearson's correlation analysis. Moreover, the highest and lowest mean values of the parameters in different areas were considered, and their spatial relationships were analyzed.
Response of upper ocean currents to typhoons at two ADCP moorings west of the Luzon Strait
We deployed two ADCP mooring systems west of the Luzon Strait in August 2008, and measured the upper ocean currents at high frequency. Two typhoons passed over the moorings during approximately one-month observation period. Using ADCP observations, satellite wind and heat flux measurements, and high-resolution model assimilation products, we studied the response of the upper ocean to typhoons. The first typhoon, Nuri, passed over one of the moorings, resulting in strong Ekman divergence and significant surface cooling. The cooling of surface water lagged the typhoon wind forcing about one day and lasted about five days. The second typhoon, Sinlaku, moved northward east of the Luzon Strait, and did not directly impact currents near the observation regions. Sinlaku increased anomalous surface water transport exchange across the Luzon Strait, which modulated the surface layer current of the Kuroshio.