Typhoon Hato Research Articles

Characterizing interactive compound flood drivers in the Pearl River Estuary: A case study of Typhoon Hato (2017)

Tropical cyclone (TC) induced compound floods involve dynamic interactions among astronomical tides, storm surges, precipitation, and associated river pulses. This study employs a one-way coupled WRF, Delft3D, and HEC-RAS model to investigate the impacts of oceanic, pluvial, and fluvial processes on compound flood dynamics during Typhoon Hato (2017) in the Pearl River Estuary (PRE), South China. Total water levels driven by different combinations of flood drivers are modeled and analyzed. Relative contributions of each type of flood driver are quantified and used to categorize flood zones. This study highlights the persistent impacts of storm surges and their nonlinear interactions with other flood drivers. They can modify both the timing and magnitude of maximum water levels, thereby distorting tidal signals and contributing to post-TC landfall water level peaks. Along coastal regions, water levels exhibit three successive peaks, predominantly driven by storm surge, rainfall, and the combined actions of both factors, respectively. In upstream regions and coastal areas sheltered from islands, a singular water level peak arises exclusively from rainfall-runoff processes. Moreover, nonlinear interactions between surge and rainfall-runoff have non-negligible impacts on the relative contribution of individual flood drivers, which underscores the necessity of considering both rainfall and storm surge in modeling compound flood water levels. During the flooding period, peak storm surge and the following peak rainfall resulted in a time-varying distribution of flood zones. Alternating feedback between compounded and ocean-dominant areas manifests in the midsections of the upper PRE. Maximum flooding depth, extent, and duration are mainly influenced by rainfall. Storm surges play a secondary role, causing intense but short-lived flooding in coastal regions. These findings aid in understanding the generation mechanism of compound floods and provide references for hazard mitigation strategies.

Nonlinear Tide‐River‐Surge Interactions and Their Impacts on Compound Flooding During Typhoon Hato in the Pearl River Delta

AbstractIn coastal areas, multiple hydrodynamic processes co‐occur, including the astronomical tide, river discharge, and storm surge. Their propagation and interaction within coastal tidal river result in strong nonlinear behavior in inland areas. This study employed a hydrodynamic model and continuous wavelet transform analysis to investigate the complex tide‐river‐surge interactions and their impacts on compound flooding in the West River of the Pearl River Delta during an extreme typhoon event. Validated model outputs provided insights into the spatial and temporal variations of river discharge, water levels, and currents. Wavelet analysis revealed river discharge modulates tidal properties, causing nonstationary tides and asymmetries, with high flows suppressing tidal ranges but facilitating energy transfers to overtides. During Typhoon Hato, storm surges dominated high‐frequency water level fluctuations that rapidly propagated upstream. Crucially, strong high‐frequency tide‐river‐surge coupling induced significant water level amplifications, with interaction intensities increasing landward. In upstream areas where riverine and coastal drivers converged, flood risks exceeded typical estimates due to this vigorous multi‐driver compounding. Findings highlighted how existing flood mitigation approaches over simplistically superposing individual sources may severely underestimate flood levels by neglecting such nonlinear interactions. A comprehensive accounting of the cumulative, multiplicative effects of tides, discharge, storm surge, and sea level rise is imperative. This quantitative unraveling of key physical drivers offers transferable insights applicable to compound flood risk evaluations and policy guidance for enhancing resilience in other estuary and delta regions. Future work should focus on holistically modeling multivariate extremes and their interactions.

Impacts of Large-Scale Offshore Wind Farms on Tropical Cyclones: A Case Study of Typhoon Hato

Abstract With the rising global demand for renewable energy sources, a great number of offshore wind farms are being built worldwide, as well as in the northern South China Sea. There is, however, limited research on the impact of offshore wind farms on the atmospheric and marine environment, particularly tropical cyclones, which frequently occur in summertime in the South China Sea. In this paper, we employ the Weather Research and Forecasting (WRF) Model to investigate the impacts of large-scale offshore wind farms on tropical cyclones, using the case of Typhoon Hato, which caused severe damage in 2017. Model results reveal that maximum wind speeds in coastal areas decrease by 3–5 m s−1 and can reach a maximum of 8 m s−1. Furthermore, the wind farms change low-level moisture convergence, causing a shift in the precipitation center toward the wind farm area and causing a significant overall reduction (up to 16%) in precipitation. Model sensitivity experiments on the area and layout of the wind farm have been carried out. The results show that larger wind farm areas and denser turbine layouts cause a more substantial decrease in the wind speed over the coast and accumulated precipitation reduction, further corroborating our findings. Significance Statement This study holds significant implications for developing offshore wind farms in tropical cyclone-prone regions like the South China Sea. By focusing on Typhoon Hato as a case study, the research sheds light on the previously understudied relationship between large-scale offshore wind farms and tropical cyclones. The observed decrease in coastal wind speeds and altered precipitation patterns due to wind farm presence highlights the potential for mitigating cyclone-related risks in these regions. Additionally, the study’s sensitivity experiments underscore the importance of careful planning and design in optimizing wind farm layouts for maximum impact reduction. This research contributes vital insights into sustainable energy infrastructure development while minimizing environmental and meteorological risks in cyclone-prone areas.

The Effects of Upper-Ocean Sea Temperatures and Salinity on the Intensity Change of Tropical Cyclones over the Western North Pacific and the South China Sea: An Observational Study

With increasing air and sea temperatures, the thermodynamic environments over the oceans are becoming more favourable for the development of intense tropical cyclones (TCs) with rapid intensification (RI). The South China coastal region consists of highly densely populated cities, especially over the Pearl River Delta (PRD) region. Intense TCs maintaining their strength or the RI of TCs close to the coastal region can present substantial forecasting challenges and have significant potential impacts on the coastal population. This study investigates the effect of sea-surface and sub-surface temperatures and salinity on the intensification of five TCs, namely Super Typhoon Hato in 2017, Super Typhoon Mangkhut in 2018, and Typhoon Talim, Super Typhoon Saola, and Severe Typhoon Koinu in 2023, which have significantly affected the South China coastal region and triggered high TC warning signals in Hong Kong in the past few years. This analysis utilised the Hong Kong Observatory’s TC best-track and intensity data, along with sea temperature and salinity profiles generated using the China Ocean ReAnalysis version 2 (CORA2) product from the National Marine Data and Information Service of China. It was found that high sea-surface temperatures (SST) of 30 °C or above for a depth of about 20 m, low sea-surface salinity (SSS) levels of 33.8 psu or below for a depth of at least 20 m, and strong salinity stratification of at least 0.6 psu per 100 m depth might offer useful hints for predicting the RI of TCs over the western North Pacific and the South China Sea (SCS) in operational forecasting, while noting other contributing environmental factors and synoptic flow patterns conducive to RI. This study represents the first documentation of sub-surface salinity’s impact on some intense TCs traversing the SCS during 2017–2023 based on an observational study. Our aim is to supplement operational techniques for forecasting RI with some quantitative guidance based on upper-level ocean observations of temperatures and salinity, on top of well-known but more rapidly changing dynamical factors like low-level convergence, weak vertical wind shear, and upper-level divergent outflow, as forecasted with numerical weather prediction models. This study will also encourage further research to refine the analysis of quantitative contributions from different RI factors and the identification of essential features for developing AI models as one way to improve the forecasting of TC RI before the TC makes landfall near the PRD, with due consideration given to the effect of freshwater river discharge from the Pearl River.

Revisiting the Ionospheric Disturbances Over Low Latitude Region of China During Super Typhoon Hato

AbstractThe ionosphere exhibits complex variations due to the influences from above and below. To distinguish the source of ionospheric disturbances is important for understanding the variation process and the coupling mechanism among different regions. Using the ionospheric total electron content (TEC) derived from Global Navigation Satellite System observations, the ionospheric disturbances during the super typhoon Hato in 2017 that was accompanied by a weak geomagnetic storm are revisited, including the ionospheric deviation and traveling ionospheric disturbances (TIDs). It is found that the ionospheric TEC in the low‐latitude region of China experienced a significant enhancement (200% compared to the quiet geomagnetic day) on Hato landing day. This enhancement covers the northern and southern equatorial ionization anomaly (EIA) region from 80°E to 180°E. Considering the geomagnetic condition, the hmF2 and the O/N2 ratio in thermosphere, it is concluded that this enhancement is not related to the typhoon, but to the coinciding weak geomagnetic storm. Additionally, several medium‐scale TIDs are verified from differential TEC data in China low latitude region during Hato period. Most of them occur after sunset and their propagating direction is southwest that often occur in East‐Asian sector in summer months, which are not related to the typhoon. While a few TIDs with concentric wavefront (Concentric TIDs) are also observed on the day before Hato landfall that should be excited in the deep convective region of the typhoon. Because the ionosphere is affected by disturbances both from above and below, it should be careful to determine the source of the ionospheric disturbances.

Energy flux variations and safety assessment of offshore wind and wave resources during typhoons in the northern South China Sea

Extreme ocean conditions during typhoons pose significant challenges to the sustainable utilization of ocean renewable energy. This study focuses on analyzing the wind and sea states within typhoon systems and the variations in offshore wind & wave energy flux during typhoons passing over the northern South China Sea (SCS) from 2000 to 2022. The trajectories and intensities of 769 typhoons in the Western Pacific, along with wind & wave energy flux variations during 155 instances of typhoons making landfall in the SCS, are isolated for comprehensive analysis. Specifically, the safety of energy exploitation during severe typhoon Hato (2017) is assessed considering the local met-ocean condition during typhoon passing and the survival ocean conditions of Offshore Wind Turbines (OWTs) and Wave Energy Converters (WECs). The WRF model and FVCOM-SWAVE model are used to provide necessary winds and waves during the passage of Hato with simulations validated against observations for reliable safety assessments. The results show that, over the past 22 years, the regions spanning from northern Guangdong to the Luzon Strait have been subjected to robust winds and formidable waves. The average values of Wind Power Density (WPD) and Wave Power Flux (WPF) during typhoons have exceeded 1500 W/m2 and 20 kW/m, respectively. In the Hato typhoon system, the maximum wind speed surpasses 60 m/s, while the significant wave height is about 10 m. Moreover, the survival capabilities of current OWTs (MySE5.5-155, SWT-6.0-154, SWT-7.0-154, SG 8.0–167 DD and D10000-185) and WECs (Sea Power and CycWEC) are assessed, demonstrating their ability to withstand the entire typhoon lifetime. Therefore, OWTs and WECs exhibit robust survival capabilities through comprehensive assessments based on the validated numerical simulation results, facing extreme typhoon conditions.

Simulating the impact of typhoons on air‐sea CO2 fluxes on the northern coastal area of the South China Sea

The South China Sea is a typhoon-prone region, and previous studies have shown that typhoons have significant impacts on air-sea CO2 fluxes. However, the effect of typhoons on the northern coastal area of the South China Sea is not well understood owing to limited observational data. In this study, we used a coupled model to simulate the impact of four typhoons (Hato, Mangkhut, Nida, and Merbok) on the partial pressure of CO2 in seawater (pCO2sea) and the CO2 fluxes in this area. Our results show that the coupled model effectively reproduces the spatial pattern of pCO2sea in this region. The response of pCO2sea to typhoons was determined by typhoon-induced vertical mixing and coastal upwelling, along with initial oceanic conditions. Typhoon Nida caused a decrease in pCO2sea with Total Alkalinity and Sea Surface Temperature being the primary factors. However, typhoons Hato, Mangkhut, and Merbok caused an increase in pCO2sea with Dissolved Inorganic Carbon playing a more prominent role. The average CO2 fluxes during the passage were approximately 6–14 times higher than those before typhoon passage. These results enhance our understanding of the effect of typhoons on air-sea CO2 fluxes over the northern coastal area of the South China Sea.

Effect of land cover pattern on rainfall during a landfalling typhoon: A simulation of Typhoon Hato

The impact of urbanization on weather events has received increasing attention. Taking Typhoon Hato as an example, the impact of anthropogenic land cover change on typhoon landfall and sequential rainfall is quantified in this study. A numerical model is first built based on the Weather Research and Forecast model. Then, the model is validated, the performance of parameters for the different meteorological and microphysical processes is assessed and a set of optimal parameters are selected. After that, the responses of typhoon and the corresponding rainfall to land cover patterns under three conditions of no urbanization, current urbanization and future urbanization in Pearl River Delta are simulated and compared. Verification experiments show that it is necessary to consider the microphysical process to enhance the accuracy of typhoon simulation. The dramatic change of land cover has limited influence on typhoon tracks. However, the urbanized land surface promotes typhoon rainfall significantly. The hourly rainfall rate under the urbanization condition is about double that under the no urbanization condition. With the intensifying urbanization in the future, the maximum hourly rainfall rate will increase by 21%. The urban heat island effect almost disappears as Typhoon Hato approaches the inland region, and the urban dynamic effect plays an important role in typhoon rainfall. The intensified rainfall is related to the retention of typhoon caused by rough surface of the city. The wind speed under the condition of no urbanization is in general 2 m/s greater than that under the urbanization condition. The increase in surface roughness reduces the typhoon movement speed and more rainfall is generated. With the development of urbanization, intensified rainfall at typhoon landfall needs to be paid more attention to.

An integrative modelling framework for predicting the compound flood hazards induced by tropical cyclones in an estuarine area

In this study, a novel numerical model is first developed, which can simulate compound floods under a framework comprehensively considering the combined effects of tide, river flow, rainfall, and wind. The modelling framework is applied to reproduce an extreme compound flood event in the Pearl River Delta caused by Typhoon Hato (2017). The model is estimated to perform reasonably well, which can yield consistent results compared with observations including winds, water levels, and inundation depths over the study area. Inundation was concentrated on downstream estuaries and floodplains and coastal forcings played a dominant role in this compound event. However, ignoring river and rainfall contributions would result in an underestimation of flood extent and water levels that could be up to 48%. Sensitivity tests indicate that precise calibration of the roughness coefficient is more critical in river and estuarine environments than in land region. This study demonstrates the importance of utilizing an integrative framework to assess and predict compound flooding hazards driven by the effects of tropical cyclones.

Key ingredients in regional climate modelling for improving the representation of typhoon tracks and intensities

Abstract. There is evidence of an increased frequency of rapid intensification events of tropical cyclones (TCs) in global offshore regions. This will not only result in increased peak wind speeds but may lead to more intense heavy precipitation events, leading to flooding in coastal regions. Therefore, high impacts are expected for urban agglomerations in coastal regions such as the densely populated Pearl River Delta (PRD) in China. Regional climate models (RCMs) such as the Weather Research and Forecasting (WRF) model are state-of-the-art tools commonly applied to predict TCs. However, typhoon simulations are connected with high uncertainties due to the high number of parameterization schemes of relevant physical processes (including possible interactions between the parameterization schemes) such as cumulus (CU) and microphysics (MP), as well as other crucial model settings such as domain setup, initial times, and spectral nudging. Since previous studies mostly focus on either individual typhoon cases or individual parameterization schemes, in this study a more comprehensive analysis is provided by considering four different typhoons of different intensity categories with landfall near the PRD, i.e. Typhoon Neoguri (2008), Typhoon Hagupit (2008), Typhoon Hato (2017), and Typhoon Usagi (2013), as well as two different schemes for CU and MP, respectively. Moreover, the impact of the model initialization and the driving data is studied by using three different initial times and two spectral nudging settings. Compared with the best-track reference data, the results show that the four typhoons show some consistency. For track bias, nudging only horizontal wind has a positive effect on reducing the track distance bias; for intensity, compared with a model explicitly resolving cumulus convection, i.e. without cumulus parameterization (CuOFF; nudging potential temperature and horizontal wind; late initial time), using the Kain–Fritsch scheme (KF; nudging only horizontal wind; early initial time) configuration shows relatively lower minimum sea level pressures and higher maximum wind speeds, which means stronger typhoon intensity. Intensity shows less sensitivity to two MP schemes compared with the CuOFF, nudging, and initial time settings. Furthermore, we found that compared with the CuOFF, using the KF scheme shows a relatively larger latent heat flux and higher equivalent potential temperature, providing more energy to typhoon development and inducing stronger TCs. This study could be used as a reference to configure WRF with the model's different combinations of schemes for historical and future TC simulations and also contributes to a better understanding of the performance of principal TC structures.

Integrating physics-informed machine learning with resonance effect for structural dynamic performance modeling

Accurate prediction the dynamic response of structures under various loads is a complex and challenging task due to the uncertainties and intricacies of loading scenarios and analysis methods. Traditional approaches to structural analysis and modeling often rely on physics-based simulations, which can be computationally expensive and time-consuming. Over the years, Machine Learning (ML) methods have proven to be a formidable tool for data-driven modeling, based on in-situ monitoring data. However, these ML models are generally purely data-driven, lacking consideration for relevant physical information such as dynamic characteristics. Hence, this paper proposes a Physics-Informed Machine Learning (PIML) approach for modeling structural dynamic performance. This method embeds resonance effect, a crucial piece of physical information in real-world engineering, into the design of the multilayer perceptron (MLP) loss function. The model is validated through numerical simulations of forced vibrations in a single-degree-of-freedom system and a vehicle-bridge coupled system. The results indicate that the proposed PIML can model the system dynamic response effectively and simulate resonance effect at key frequency-domain locations accurately. Subsequently, features are extracted from the real-world monitoring data of a high-rise building dynamic response during Typhoon Hato, and PIML is applied for training. The results reveal that PIML significantly outperforms pure ML algorithms, even with a small dataset, and can effectively capture resonance effect in wind-induced vibrations. Using a well-trained PIML, a parameter analysis is conducted, comparing the dynamic performance under different wind speeds and frequency conditions. Lastly, considering the variation in wind parameters due to climate change, PIML is employed to analyze long-term structural fragility. The findings indicate significant changes in fragility from 1985 to 2045. In conclusion, the proposed PIML algorithm offers several advantages over conventional methods, such as reduced computational costs, improved accuracy, and the ability to capture complex nonlinear behaviors and resonance effect of interest, and efficiently serve in analyses of structural reliability and fragility.

Different responses of two adjacent artificial beaches to Typhoon Hato in Zhuhai, China

Different responses of two adjacent artificial beaches to Typhoon Hato in Zhuhai, China

Investigating the Storm Surge and Flooding in Shenzhen City, China

Tropical cyclones affecting Shenzhen city have shown a remarkable tendency to increase in both intensity and quantity, highlighting the urgency of accurate forecasts of storm surges and flooding for effective planning and mitigation. Utilizing satellite and field observations together with the advanced high-resolution baroclinic wave–current model (SCHISM), a comprehensive investigation aimed at storm surge and flooding in Shenzhen was conducted. Statistical work of historical tropical cyclones revealed that Shenzhen was most vulnerable to cyclones propagating from the southeast toward the northwest and passing Shenzhen down the Pearl River Estuary. Thus, a representative, i.e., super typhoon Hato (2017), was selected for further study. Validations of numerical results suggested satisfactory model performance in mapping the wave, tide, and surge processes. Remarkable differences in spatiotemporal distribution and intensity of storm surge and flooding were found along the Shenzhen coast, which was dominated by the propagation of far-field surge and tidal waves, cooperation between wind direction and coastline orientation, estuary morphology, and the land terrain. Intervention of wave–current interaction improved the simulation of the surge and flooding and triggered an earlier occurrence time of the maximum surge in specific areas. The Pearl River discharge significantly elevated the sea level height inside the estuary and contributed to a more severe surge. Given the extremely complicated river networks and huge freshwater flux of Pearl River and the increasing trend of concurrent heavy precipitation of tropical cyclones, future investigations on compound flooding were suggested.

Damage by typhoon Hato compared among three different plant communities in Macau, China.

Tropical cyclones are among the major climatic disasters threatening human survival and development. They are also responsible in part for forest taxonomic composition and dynamics and may lead to catastrophic succession between ecosystems. In this study, we aimed to investigate the extensiveness and severity of the effect caused by Typhoon Hato among the three primary plant communities in Macau, China, including Guia Hill, Taipa Grande, and Ka Ho. The plants' damage was classified into seven categories, ranging from Degree 6, which represents the most severe damage, to Degree 0, which represents almost no damage. The impact of Typhoon Hato was evaluated at different levels, including sample plots, species, DBH, and community structure. Our results show that the sub-climax community of Guia Hill was most disturbed, with the highest damage index (DI) of 55.28%. Similarly, the Ka Ho shoreline shrub community was also considerably influenced, with a DI of 48.14%. By contrast, the managed secondary forest around Taipa Grande was the least affected, with a DI of 32.66%. Additionally, from the tree layer perspective, the tall trees at Guia Hill canopy layer were directly affected by wind, while the dense understory layer suffered from severe secondary damage due to the fallen trees and branches. For Taipa Grande, the dominant species in the canopy layer were shorter and had less direct damage; the secondary damage was also small as a consequence. Ka Ho had more dwarfed and multibranched species surviving from the sea breeze since Ka Ho was close to the sea. The dense plant structure in Ka Hoprotected plants from being easily broken by typhoons, but some twigs and leaves were lost. Some less damaged local species and easily recovered species found in this study could inform the selection of wind-resistant species for the typhoon-affected communities.

Outer Rainband Formation on Land Ahead of Typhoon Hato (2017)

AbstractAn outer rainband develops rapidly on land of South China from afternoon to evening of 22 August 2017 when Typhoon Hato is approaching, leading to an early arrival of convective storms prior to typhoon's landfall. The convective cells initiate on the eastern coasts and move to the western inland region where they grow upscale into a fully fledged outer rainband. Convective‐permitting simulations suggest that the new‐born convective cells on the eastern coasts are associated with the increasing convective instability and low‐level lifting by the land‐sea differences of non‐gradient winds. Such differences are established by the horizontal and vertical components of thermal contrasts. In the following stage of convection organization, the convectively induced cold pools in turn strengthen the updrafts at their leading edges, which help to organize the convective cells on rainband as a fast‐moving squall line in the western region. Such storm‐feedback processes of rainband convection and cold pools strongly respond to the changing convective instability and mid‐level dry conditions on land. These regional environmental conditions are closely associated with the large‐scale subsidence in the outer region of typhoon. The results highlight that the new outer rainband can form rapidly on land due to surface heating, and the storm‐feedback processes in response to the changing environmental conditions when a tropical cyclone is approaching land.

Optimal design of a glider array for the observation of tropical cyclones

Underwater gliders have advantages for typhoon observation. In recent years, the typhoon-resistant operation mode and cluster networking capabilities of such platforms have improved greatly; therefore, underwater gliders have received increasing attention for typhoon observation, no matter observing the salinity, density, or temperature of the seawater during the typhoon. However, there is a lack of scientific evaluation of the sampling layout and planning of underwater gliders during tropical cyclones (TCs). Based on the simulation results of the three-dimensional Price–Weller–Pinkel numerical model (3DPWP) for Typhoon Hato, this study considers the working characteristics of underwater gliders to model the sampling results and for the first time proposes a method of evaluate the simulated typhoon observation effect of underwater gliders. Subsequently, four kinds of heading schemes for an underwater glider array are designed and evaluated, and the optimal design of a glider array for typhoon observation, that is, the “along-typhoon parallel” mode, is identified through comparison. Finally, the optimal design employing a genetic algorithm is applied to Typhoon Hato to verify its universality and effectiveness. Underwater gliders with the best typhoon observation scheme are helpful to more completely observing and reconstructing the 3D structure of the tropical-cyclone-induced ocean response with greater precision.

An Observational Study of Short‐Cycle Lightning Outbreaks in the Inner Core of Typhoon Hato (2017) Before Landfall

AbstractThis study analyzes microphysical signatures relevant to the short‐cycle lightning activity in the inner core of Typhoon Hato (2017) before landfall in China. Observations reveal that the lightning bursts were accompanied by enhanced inner‐core convection with a behavior cycle of about 3 hr. The coupling between wavenumber‐2 vortex Rossby waves (VRWs) and shear‐forced convective asymmetries resulted in a local updraft enhancement. Furthermore, supercooled liquid water droplets invigorated a striking enhancement of graupel via riming immediately above the freezing level, further enhancing charge separation and lightning generation outside the eyewall. Furthermore, when similar phase‐locking was associated with other propagating VRWs, graupel and updraft volumes were significantly boosted, leading to short‐cycle lightning outbreaks in the inner core.

Quantification of the nonlinear interaction among the tide, surge and river in Pearl River Estuary

The increase in storm surge and compound flood events caused by climate change exacerbates adverse effects on the estuaries. The ADCIRC + SWAN coupled model was simulated using various scenario simulations based on Super Typhoon Hato to quantify the nonlinear interactions of tide-surge-river during extreme events. The results reveal that three drivers, including (1) tide-surge phases, (2) typhoon tracks and wind speeds (3) upstream runoff, affect the extreme water levels by different nonlinear interactions. Changes in tide-surge phases remain the most constructive factor controlling nonlinear effects, with the maximum contribution exceeding 50.46% of the extreme water level. The tide-surge nonlinear residual water level contributing to the extreme water level at high tide falling can reach 0.92 m. The nonlinear effects are exacerbated as typhoon wind speeds and upstream discharges increase. Peak water levels from the compound floods are more than 25% higher than storm surges alone at the river outlets. The nonlinear effects are mainly generated by the convection terms from the tide-surge-river interactions in the estuarine rivers.

A System-Theory and Complex Network-Fused Approach to Analyze Vessel–Wind Turbine Allisions in Offshore Wind Farm Waters

Given the national goal of “emission peaking and carbon neutralization”, China has become the largest country in the world for offshore wind farm construction. At the same time, navigational safety problems in offshore wind farm waters have become increasingly frequent. Owing to the complexity of offshore wind farm waters and the small number of accident data samples available for reference, the system theory method is more suitable for selection than the traditional method. Based on causal analysis based on system theory (CAST) and a complex network (CN), in this study, a qualitative and quantitative accident analysis model, CAST-CN, is constructed to analyze a complete case of vessel and wind turbine allision in offshore wind farm waters. The results show that, at the micro level, in addition to the master, crew, shipping company, and typhoon Hato, the maritime safety administration and the wind farm operation management department have a certain impact on the development of the accident discussed in this study. At the macro level, internal and external factors leading to the lack of system safety are identified, and measures and suggestions for system safety improvement are proposed based on analysis. This study can fill the research gap in the systematic analysis of traffic accidents in offshore wind farm waters and provide support for the safety assessment and decision-making of government management departments and research institutes.

Typhoons and their upper ocean response over South China Sea using COAWST model

The formation and intensification of typhoons is a complex process where energy and mass exchanges happen between the ocean and the atmosphere. In most typhoon numerical studies, a static ocean and a dynamic atmosphere are used to reduce the complexity of modeling. Using the COAWST model, we studied the air-sea interactions of Typhoon Mujigae in 2015, Typhoon Merbok in 2017, and Typhoon Hato in 2017 over the South China Sea. With different translation speeds, track shapes, and intensities between these cyclones, they act as an excellent case study to analyze the air-sea coupling in the models. The inclusion of coupling between the ocean and atmosphere is found to improve the typhoon track simulation significantly. The bias in the cyclone tracks is reduced by 10%–40% in the coupled model. The upper ocean response to the typhoon was also analyzed using the coupled model output. The coupled simulations show that the major energy extraction occurs to the right of the track, which is consistent with satellite observation and latent heat release analysis. The coupling process shows the air-sea interactions and exchanges in the upper ocean along with the energy released during the passage of typhoons. The heat budget analysis shows that the cooling of the upper ocean is mainly attributed to the advection associated with the typhoon forcing. This study shows that it is necessary to include ocean feedback while analyzing a typhoon, and the application of coupled models can improve our understanding as well as the forecasting capability of typhoons.