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Volume 37 ， Issue 6 ， 2019
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- Abstract：The effect of the drag coefficient on a typhoon wave model is investigated. Drag coefficients for Pingtan Island are derived from the progress of nine typhoons using COARE 3.0 software. The wind parameters are obtained using the Weather Research and Forecasting model. The simulation of wind agrees well with observations. Typhoon wave fields are then simulated using the third-generation wave model SWAN. The wave model includes exponential and linear growths of the wind input, which determine the wave-growth mode. A triple triangular mesh is adopted with spatial resolution as fine as 100 m nearshore. The SWAN model performs better when using the new drag coefficient rather than the original coefficient.Keywords：drag coefficient;typhoon wind;typhoon wave;numerical simulation7|2|2Updated：2023-05-20
- Abstract：In this study, typhoon waves generated during three typhoons (Damrey (1210), Fung-wong (1416), and Chan-hom (1509)) in the Yellow Sea and East China Sea were simulated in a simulating waves nearshore (SWAN) model, and the wind forcing was constructed by combining reanalyzed wind data with a Holland typhoon wind model. Various parameters, such as the Holland fitting parameter (B) and the maximum wind radius (R), were investigated in sensitivity experiments in the Holland model that affect the wind field construction. Six different formulations were considered and the parameters determined by comparing the simulated wind results with in-situ wind measurements. The key factors affecting wave growth and dissipation processes from deep to shallow waters were studied, including wind input, whitecapping, and bottom friction. Comparison with in-situ wave measurements suggested that the KOMEN scheme (wind input exponential growth and whitecapping energy dissipation) and the JONSWAP scheme (dissipation of bottom friction) resulted in good reproduction of the significant wave height of typhoon waves. A preliminary analysis of the wave characteristics in terms of wind-sea and swell wave revealed that swell waves dominated with the distance of R to the eye of the typhoon, while wind-sea prevailed in the outer region up to six to eight times the R values despite a clear misalignment between wind and waves. The results support the hypothesis that nonlinear wave-wave interactions may play a key role in the formation of wave characteristics.Keywords：Holland;Simulating WAves Nearshore (SWAN);typhoon waves;Yellow Sea;East China Sea;wind-sea;swell5|2|7Updated：2023-05-20
- Abstract：As concluded from physical theory and laboratory experiment, it is widely accepted that nonlinearities of sea state play an important role in the formation of rogue waves; however, the sea states and corresponding nonlinearities of real-world rogue wave events remain poorly understood. Three rogue waves were recorded by a directional buoy located in the East China Sea during Typhoon Trami in August 2013. This study used the WAVEWATCH Ⅲ model to simulate the sea state conditions pertaining to when and where those rogue waves were observed, based on which a comprehensive and full-scale analysis was performed. From the perspectives of wind and wave fields, wave system tracking, High-Order Spectral method simulation, and some characteristic sea state parameters, we concluded that the rogue waves occurred in sea states dominated by second-order nonlinearities. Moreover, third-order modulational instabilities were suppressed in these events because of the developed or fully developed sea state determined by the typhoon wave system. The method adopted in this study can provide comprehensive and full-scale analysis of rogue waves in the real world. The case studied in this paper is not considered unique, and rules could be found and confirmed in relation to other typhoon sea states through the application of our proposed method.Keywords：rogue wave;wave system tracking;high-order spectral method;nonlinear effect4|2|2Updated：2023-05-20
- Abstract：The transport flux residue of surface waves plays an important role in a variety of ocean phenomena, for example, the change in sea surface temperature (SST) and upper mixed layer profile that were studied in a series of recent papers. In the previous studies, its effect was discussed rigorously and fragmented based on numerical modeling. Here we propose a relatively comprehensive and simplified exposition of the wave transport flux residue, and focus on its influence under typhoon conditions with strong background current. An analogue Reynolds Number is presented for tentative comparison with wave-generated turbulence mixing, especially in the coastal area. Numerical results indicate that both overwhelming dynamical mixing processes can remarkably change the coastal environment, and should not be ignored consciously for further marine hazards assessment.Keywords：wave transport flux residue;decomposition scheme;Analogue Reynolds Number4|2|2Updated：2023-05-20
- Abstract：Accurate estimation of wave uplift force is essential to the designs of reliable coastal and marine structures. We presents a series of laboratory work here on the impact of regular waves on horizontal panels,from which an empirical formula to estimate accurately the wave uplift force on panels is established. The laboratory measurements show that the wave uplift force depends mainly on the incident wave height,the wave period,the wave length,the panel width,and the clearance between the subsurface of the panel and the still water level. Among these factors,the impact of the panel width on uplift forces is relatively complicated. Result shows that the relative panel width (i.e.,the ratio of panel width to wave length) plays a more important role in estimating the wave uplift force. Based on our comprehensive laboratory measurements,we further developed an empirical formula to compute wave uplift force on horizontal panels through dimensionless analysis. Compared with other empirical formulas,this formula uses dimensionless variables of clear physical meanings,thus can describe the interaction between waves and the panels in a better way. In addition,the efficiency of the formula to estimate wave uplift force on horizontal panels is verified against existing works. Therefore,the findings in this study shall be useful for understanding the mechanism of wave uplift force on horizontal panels and numerical model validation.Keywords：laboratory experiment;wave-structure interaction;horizontal panels;wave uplift force;empirical formula4|2|1Updated：2023-05-20
- Abstract：In the context of global climate change,the impact of group-occurring ocean dynamic disasters on China's offshore areas is becoming more and more intense. The study of the effect of existing ocean dynamic disasters on offshore hazard-bearing bodies mostly focuses on the effect of single disaster-causing factors,and it is still insufficient to study storm surge and dynamic wave coupling & reinforcement effects as well as the process of the dynamic response of such hazard-bearing bodies as seawalls. This study firstly realized the synchronous process of water level and wave through continuous tide generation and wave generation by the wave maker and tide generating device,so as to realize the dynamic coupling simulation of storm surge and wave in the laboratory. Then the physical model test of the typical seawall section was carried out under the dynamic coupling of storm surge and wave as well as at a conventional fixed water level respectively. In the process of test wave overtopping discharge and the damage process of the levee crown and backwall of seawalls were observed and compared,and their damage mechanism was also studied.Keywords：sea dike;storm surge;wave;overtopping wave;levee overflowing;coupling4|2|3Updated：2023-05-20
- Abstract：In recent years, fast economic development demands for more land use and thus many reclamation projects are initiated around the Sanmen Bay, Zhejiang, SE China in the East China Sea, for which tidal and storm surge levels are reassessed. A two-dimensional numerical model based on an advanced circulation model (ADCIRC) was applied to evaluate the impact of reclamation projects on tidal and storm surge levels in the bay. The results show that the shoreline relocation and topographic change had opposite effects on tidal heights. Shoreline relocation decreased the tidal amplitude, while siltation caused topographic change and increased the amplitude. Such variations of the amplitude were significant in the top areas of Sanmen Bay. Three types of typhoon paths were selected for a case study to investigate the impacts of shoreline relocation and topographic change on storm surge level. Results show that the maximum increase in storm surge level due to shoreline relocation was less than 0.06 m. The rise of peak surge level due to the change of topography was significant and the peak surge level rose when siltation increased. The maximum surge level rise occurred in the path of northwest landing typhoons, which exceeded 0.24 m at the top of the bay. The rise in peak surge level can potentially lead to severe damages and losses in Sanmen Bay and more attention needs to be paid to this problem of shoreline change in the future.Keywords：Sanmen Bay;reclamation project;Tidal Height;peak surge level4|2|4Updated：2023-05-20
- Abstract：Offshore waters provide resources for human beings, while on the other hand, threaten them because of marine disasters. Ocean stations are part of offshore observation networks, and the quality of their data is of great significance for exploiting and protecting the ocean. We used hourly mean wave height, temperature, and pressure real-time observation data taken in the Xiaomaidao station (in Qingdao, China) from June 1, 2017, to May 31, 2018, to explore the data quality using eight quality control methods, and to discriminate the most effective method for Xiaomaidao station. After using the eight quality control methods, the percentages of the mean wave height, temperature, and pressure data that passed the tests were 89.6%, 88.3%, and 98.6%, respectively. With the marine disaster (wave alarm report) data, the values failed in the test mainly due to the influence of aging observation equipment and missing data transmissions. The mean wave height is often affected by dynamic marine disasters, so the continuity test method is not effective. The correlation test with other related parameters would be more useful for the mean wave height.Keywords：quality control;real-time station data;marine big data;Xiaomaidao Station;marine disaster4|4|0Updated：2023-05-20
- Abstract：As one of the most serious natural disasters, many typhoons affect southeastern China every year. Taking Shenzhen, a coastal city in southeast China as an example, we employed a Monte-Carlo simulation to generate a large number of virtual typhoons for wind hazard analysis. By analyzing 67-year historical typhoons data from 1949 to 2015 using the Best Track Dataset for Tropical Cyclones over the Western North Pacific recorded by the Shanghai Typhoon Institute, China Meteorological Administration (CMASTI), typhoon characteristic parameters were extracted and optimal statistical distributions established for the parameters in relation to Shenzhen. We employed the Monte-Carlo method to sample each distribution to generate the characteristic parameters of virtual typhoons. In addition, the Yan Meng (YM) wind field model was introduced, and the sensitivity of the YM model to several parameters discussed. Using the YM wind field model, extreme wind speeds were extracted from the virtual typhoons. The extreme wind speeds for different return periods were predicted and compared with the current structural code to provide improved wind load information for wind-resistant structural design.Keywords：typhoon hazard analysis;Monte-Carlo simulation;wind field model;extreme wind speed4|1|2Updated：2023-05-20
- Abstract：Sea level rise is a slow-onset disaster. We collected information about the natural and ecological environments, tides and sea levels, and socio-economic aspects to investigate the distribution and zoning of the risks from sea level rise across Shandong Province. The trends in sea level in different counties of Shandong Province were predicted using moving averages and a random dynamic analysis forecasting model, and the model outputs and socio-economic indicators were combined to assess the risks. The results show that the risks of sea level rise along the western coast of Bohai Bay and Laizhou Bay in Shandong Province were sufficiently large to warrant attention.Keywords：sea level rise;risk assessment;risk zoning4|2|1Updated：2023-05-20
- Abstract：Line integral convolution (LIC) is a useful visualization technique for a vector field. However,the output image produced by LIC has many problems in a marine vector field. We focus on the visual quality improvement when LIC is applied in the ocean steady and unsteady flow field in the following aspects. When a white noise is used as the input in a steady flow field,interpolation is used to turn the discrete white noise into continuous white noise to solve the problem of discontinuity. The "cross" high-pass filtering is used to enhance the textures of streamlines to be more concentrated and continuity strengthened for each streamline. When a sparse noise is used as the input in a steady flow field,we change the directions of background sparse noise according to the directions of vector field to make the streamlines clearer and brighter. In addition,we provide a random initial phase for every streamline to avoid the pulsation effect during animation. The velocities of vector field are encoded in the speed of the same length streamlines so that the running speed of streamlines can express flow rate. Meanwhile,to solve the problem of obvious boundaries when stitching image,we change the streamline tracking constraints. When a white noise is used as an input in an unsteady flow field,double value scattering is used to enhance the contrast of streamlines; moreover,the "cross" high-pass filtering is also adopt instead of two-dimensional high-pass filtering. Finally,we apply the above methods to a case of the surface wave field in typhoon condition. Our experimental results show that applying the methods can generate high-quality wave images and animations. Therefore,it is helpful to understand and study waves in typhoon condition to avoid the potential harm of the waves to people's lives and property.Keywords：line integral convolution (LIC);wave data visualization;steady and unsteady marine flow field4|3|2Updated：2023-05-20
- Abstract：Because of the special topography and large tidal range in the South Yellow Sea,the dynamic process of tide and storm surge is very complicated. The shallow water circulation model Advanced Circulation (ADCIRC) was used to simulate the storm surge process during typhoon Winnie,Prapiroon,and Damrey,which represents three types of tracks attacking the South Yellow Sea,which are,moving northward after landing,no landing but active in offshore areas,and landing straightly to the coastline. Numerical experiments were carried out to investigate the effects of tidal phase on the tide-surge interaction as well as storm surge. The results show that the peak surge caused by Winnie and Prapiroon occurs 2-6 h before the high tide and its occurring time relative to high tide has little change with tidal phase variations. On the contrary,under the action of Damrey,the occurring time of the peak surge relative to high tide varies with tidal phase. The variation of tide-surge interaction is about 0.06-0.37 m,and the amplitude variations of interaction are smooth when tidal phase changes for Typhoon Winnie and Prapiroon. While the interaction is about 0.07-0.69 m,and great differences exists among the stations for Typhoon Damrey. It can be concluded that the tide-surge interaction of the former is dominated by the tidal phase modulation,and the time of surge peak is insensitive to the tidal phase variation. While the interaction of the latter is dominated by storm surge modulation due to the water depth varying with tide,the time of surge peak is significantly affected by tidal phase. Therefore,influence of tidal phase on storm surge is related to typhoon tracks which may provide very useful information at the design stage of coastal protection systems.Keywords：storm surge;Tidal Phase;tide-surge interaction;South Yellow Sea;Advanced Circulation (ADCIRC) model4|1|0Updated：2023-05-20
- Abstract：Sea ice disaster is one of the principal natural hazards that affect some coastal areas of China, and the formation of ice cover in a wave field has important characteristics. However, analysis of the mechanism in which waves affect the thermodynamic process of sea ice is lacking, and the influence of waves is not taken into consideration in numerical models of sea ice, largely because of a lack of simultaneous observations of waves and sea ice. Using observational data of the sea ice cycle in the coastal waters of Liaodong Bay (China), we analyzed the characteristics of hydrology, meteorology, and sea ice thickness during the formation of sea ice, and explored the changes in the interrelationships among heat fluxes, waves, and sea ice under actual sea conditions. The results could provide a decision-making support as a reference to the establishment and improvement of China's early warning system to sea ice disasters, and the protection of ice drilling operations and production platform safety.Keywords：wave;sea ice;wave-induced turbulence kinetic energy5|3|2Updated：2023-05-20
- Abstract：Sea ice can attenuate wave energy significantly when waves propagate through ice covers. In this study, a third-generation wave model called simulating wave nearshore (SWAN) was advanced to include damping of wave energy due to friction in the boundary layer below the ice. With the addition of an eddy viscosity wave-ice model, the resulting new SWAN model was applied to simulate wave height in the Bohai Sea during the freezing winter. Its performance was validated with available buoy data near the ice edge, and the new model showed an improvement in accuracy because it considered the ice effect on waves. We then performed a wave hindcast for the Bohai Sea during a freezing period in the winter of 2016 that had the severest ice conditions in recent years and found that the mean significant wave height changed by approximately 16.52%. In the Liaodong Bay, where sea ice concentration is highest, the change reached 32.57%, compared with the most recent SWAN model version. The average influence of sea ice on wave height simulation was also evaluated over a five-year (2013-2017) hindcast during January and February. We found that the wave height decrease was more significant in storm conditions even the eddy viscosity wave-ice model itself showed no advantage on damping stronger waves.Keywords：eddy viscosity wave-ice model;simulating wave nearshore (SWAN);Bohai Sea;ice-induced wave damping4|2|1Updated：2023-05-20
- Abstract：When investigating the long-term variation of wave characteristics as associated with storm surges in the Bohai Sea, the Simulating Waves Nearshore (SWAN) model and ADvanced CIRCulation (ADCIRC) model were coupled to simulate 32 storm surges between 1985 and 2014. This simulation was validated by reproducing three actual wave processes, showing that the simulated significant wave height (SWH) and mean wave period agreed well with the actual measurements. In addition, the long-term variations in SWH, patterns in SWH extremes along the Bohai Sea coast, the 100-year return period SWH extreme distribution, and waves conditional probability distribution were calculated and analyzed. We find that the trend of SWH extremes in most of the coastal stations was negative, among which the largest trend was -0.03 m/a in the western part of Liaodong Bay. From the 100-year return period of the SWH distribution calculated in the Gumbel method, we find that the SWH extremes associated with storm surges decreased gradually from the center of the Bohai Sea to the coast. In addition, the joint probability of wave and surge for the entire Bohai Sea in 100-year return period was determined by the Gumbel logistic method. We therefore, assuming a minimum surge of one meter across the entire Bohai Sea, obtained the spatial SWH distribution. The conclusions of this study are significant for offshore and coastal engineering design.Keywords：significant wave height (SWH);storm surge;long-term variation;coupled models;Bohai Sea4|1|5Updated：2023-05-20
- Abstract：The Radial Sand Ridges (RSRs) area in the southern Yellow Sea are subject to tropical and extratropical cyclone activities frequently, in which the special geometry feature and moving stationary tidal system result in complex storm-induced hydrodynamic processes, especially the tide-surge interactions. We studied a rare weather event influenced simultaneously by an extratropical cyclone EX1410 and Typhoon Vongfong as an example to investigate the characteristics of storm surges, wave-surge, and tide-surge interaction in the RSRs area, and applied a high-resolution integrally-coupled ADCIRC+SWAN model, in which the meteorological forcing inputs are simulated by the WRF-ARW model. The model is validated by records from 4 tide gauges and 2 wave buoys along the Yellow Sea coast. Results show that the tide-surge interactions are of considerable regional heterogeneousness. The surge curves at Lüsi (in south RSRs) and Jianggang (in middle RSRs) have abrupt falls near the time of low tide, where the peak occurrence time of interaction residuals tend to shift towards the mid-ebb period. Significant increase of bed shear stress in shallow waters was proved the dominant factor to affect the tide-surge interaction in broad tidal flats of the RSRs area. Differently, the interaction pattern in the Xiyang Trough (in north RSRs), showed a unique rising in mid-flood period due to the phase advances of real surge waves in relatively deep waters. Therefore, we suggested to the local flood risk management that the tide-surge interaction tends to alleviate the flooding risk in the RSRs area around the time of high tide, but aggravate the risk on the rising tide in the Xiyang Trough and on the falling tide in large-scale tidal flats of the southern RSRs area.Keywords：ADCIRC+SWAN model;radial sand ridges;Jiangsu coast;extratropical cyclone;tide-surge interaction4|2|4Updated：2023-05-20
- Abstract：Dike failure caused by overtopping is likely to result in major casualties and property losses. Aiming at this fact, a series of physical model experiments were conducted on stable thickness of masonry block on the inner slope of the dike. According to the erosion of block embankment with different thicknesses, the relation between the stable thickness of masonry block pitching of the inner slope and the average overtopping discharge is discussed. New equations subject to irregular waves are presented for average overtopping discharge, based upon the analysis of mean overtopping discharge and comparison of present overtopping discharge formulas at domestic and abroad. Finally, a calculation equation of the stable thickness of the dry masonry block stone of inner slope subject to irregular waves is given. In conclusion, the formula matches well with the experiment result, which is capable of functioning as an important reference for structure designs of the dike in China.Keywords：mean overtopping discharge;block revetment;inner slope;stable thickness4|1|1Updated：2023-05-20
- Abstract：In this study, an operational forecasting system of sea dike risk in the southern Zhejiang Province, South China was developed based on a coupled storm-surge and wave model. This forecasting system is important because of the high cost of storm-surge damage and the need for rapid emergency planning. A comparison with astronomical tides in 2016 and the validation of storm surges and high water marks of 20 typhoons verified that the forecast system has a good simulation ability. The system can forecast relatively realistic water levels and wave heights as shown under the parametric atmospheric forces simulated in a case study; the sea dikes in credible high risk were mainly located in the estuaries, rivers, and around the islands in the southern Zhejiang. Therefore, the forecast system is applicable in the southern Zhejiang with a support to the effective prevention from typhoon storm-surge damage.Keywords：storm surge;sea dike;operational forecast;southern Zhejiang Province;risk calculation4|2|2Updated：2023-05-20
- Abstract：Sanduao is an important sea-breeding bay in Fujian, South China and holds a high economic status in aquaculture. Quickly and accurately obtaining information including the distribution area, quantity, and aquaculture area is important for breeding area planning, production value estimation, ecological survey, and storm surge prevention. However, as the aquaculture area expands, the seawater background becomes increasingly complex and spectral characteristics differ dramatically, making it difficult to determine the aquaculture area. In this study, we used a high-resolution remote-sensing satellite GF-2 image to introduce a deep-learning Richer Convolutional Features (RCF) network model to extract the aquaculture area. Then we used the density of aquaculture as an assessment index to assess the vulnerability of aquaculture areas in Sanduao. The results demonstrate that this method does not require land and water separation of the area in advance, and good extraction can be achieved in the areas with more sediment and waves, with an extraction accuracy >93%, which is suitable for large-scale aquaculture area extraction. Vulnerability assessment results indicate that the density of aquaculture in the eastern part of Sanduao is considerably high, reaching a higher vulnerability level than other parts.Keywords：aquaculture area;vulnerability assessment;Richer Convolutional Features (RCF) network model;deep learning;high-resolution remote sensing4|2|3Updated：2023-05-20
- Abstract：Efficient and accurate access to coastal land cover information is of great significance for marine disaster prevention and mitigation. Although the popular and common sensors of land resource satellites provide free and valuable images to map the land cover, coastal areas often encounter significant cloud cover, especially in tropical areas, which makes the classification in those areas non-ideal. To solve this problem, we proposed a framework of combining medium-resolution optical images and synthetic aperture radar (SAR) data with the recently popular object-based image analysis (OBIA) method and used the Landsat Operational Land Imager (OLI) and Phased Array type L-band Synthetic Aperture Radar (PALSAR) images acquired in Singapore in 2017 as a case study. We designed experiments to confirm two critical factors of this framework:one is the segmentation scale that determines the average object size, and the other is the classification feature. Accuracy assessments of the land cover indicated that the optimal segmentation scale was between 40 and 80, and the features of the combination of OLI and SAR resulted in higher accuracy than any individual features, especially in areas with cloud cover. Based on the land cover generated by this framework, we assessed the vulnerability of the marine disasters of Singapore in 2008 and 2017 and found that the high-vulnerability areas mainly located in the southeast and increased by 118.97 km2 over the past decade. To clarify the disaster response plan for different geographical environments, we classified risk based on altitude and distance from shore. The newly increased high-vulnerability regions within 4 km offshore and below 30 m above sea level are at high risk; these regions may need to focus on strengthening disaster prevention construction. This study serves as a typical example of using remote sensing techniques for the vulnerability assessment of marine disasters, especially those in cloudy coastal areas.Keywords：coastal area;marine disaster;vulnerability assessment;remote sensing;land use/cover;objectbased image analysis (OBIA)4|0|2Updated：2023-05-20
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