Channel: Marine hydrology http://www.jto.ac.cn EN-US http://www.jto.ac.cn/EN/1009-5470/current.shtml http://www.jto.ac.cn 1009-5470 http://www.jto.ac.cn/EN/10.11978/2021080 Based on the measured wave data of the foreshore profile at the Changle beach, the variation rules of wave parameters and energy dissipation process in the tidal process are discussed using statistical analysis and spectral analysis. The results show that the wave in the observation period is mainly mixed wave, and the spectrum type of each sensor is wide, and the multi-peak oscillation is observed. In the process of shoreward propagation, the form of wave energy dissipation is changed from narrow frequency domain to broad frequency domain, the energy distribution tends to be dispersed, the energy of high frequency wave decreases, but the energy of low frequency wave increases, and infra-gravity wave is generated after wave breaking. There is a good correlation between the energy attenuation and the wave propagation distance in the surf zone. The energy attenuation of the broken wave in the surf zone is about 98.3%. The tidal level has obvious modulating effect on waves. The incident wave energy increases with the increase of tidal water level, and the higher the water level is, the more dispersed the distribution of incident wave energy is. There is a significant positive correlation between the effective wave height and the tidal level in the surf zone. The spectral variation of each sensor in tidal process has obvious similarity with the wave spectral variation along the profile.

]]> http://www.jto.ac.cn/EN/10.11978/2021152 In this paper, an extra-tropical storm surge in the Yangshan Port (YSP) and its coastal area caused by a strong cold front on 29th December, 2020 was investigated. Meteorological observation data was analyzed to study the development of the weather system. FVCOM-SWAVE model characterized by a high-resolution unstructured-grid with 10 m was used to simulate the storm surge. The observed tide data, wave data and current data were introduced to verify the result of simulation, and the result was proved to be accurate and credible. Maximum storm surge, maximum negative storm surge, current, total water level and wave were studied to describe the character of the extra-tropical storm surge of YSP and its coastal area. Finally, sensitive experiments were carried out to compare the contributions of mean sea level pressure (SLP), wind and wave to the maximum storm surge. The main conclusions can be summarized as follows: 1) affected by the topography of the channel, the main component of the tidal current was southeast or northwest, which was approximately parallel to the shoreline, the current velocity in the deep water channel of YSP was the highest with a value between 2.6~2.8 m·s^-1; 2) due to the influence of long term northerly gale and high SLP, the storm surge behave as a characteristics of short-term positive storm surge and long-term negative storm surge; 3) during the peak period of storm surge, the contribution of wind field to storm surge was ~ 90%, and the contribution of sea-level pressure field was approximately 5%; while during the peak period of negative storm surge, the contribution of sea-level pressure field was about 55%, the contribution of wind field was ~ 40%, In addition, the contribution of wave to both was less than 10%.

]]> http://www.jto.ac.cn/EN/10.11978/2021172 This study investigates the characteristics of the east Guangdong shelf front and its dynamical regime using in-situ measurements, satellite data, and high resolution simulations by the regional ocean modeling system (ROMS). Observation results show active upwelling thermal fronts with horizontal scale of 50km on the northern shelf of the South China Sea in summer. The horizontal temperature gradient at the front is up to 0.06 ℃∙km^-1 and is stronger than satellite observed results in the same period. The front can reach 20m depth, and has the characteristics of the order-one Richardson number. Further diagnostic analysis using ROMS model output also show that the horizontal buoyancy gradient is enhanced at the front, with order-one Richardson number, which is favorable for frontal instabilities. High-resolution simulation results indicate that driven by the southwest wind in summer, the Ekman transport across the continental shelf caused by down-front wind, will accumulate cold water of upwellings to the warm water, enhancing the horizontal buoyancy gradient and front sharpness, and change the frontal baroclinicity, which leads to negative Ertel potential vorticity (EPV). As such, the Ekman buoyancy flux caused by summer monsoon may significantly contribute to the formation and instability of the continental front in the northern South China Sea, and it has an important impact on the local dynamic environment.

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