Typhoon Wind Research Articles

Uncertainty propagation of flutter derivatives and structural damping in buffeting fragility analysis of long-span bridges using surrogate models

Buffeting of long-span bridges caused by the wind turbulence could result in problems of large deformation, fatigue, traffic safety and user comfort. The calculation of buffeting responses is greatly affected by multiple uncertainties, especially the randomness of flutter derivatives and structural damping. In buffeting analysis, these uncertainties are typically propagated using the brute-force Monte Carlo (MC) method, which requires enormous computational resources for a complicated structure involving multiple uncertainties. This study develops an efficient framework based on surrogate models to account for these uncertainties in buffeting responses and the assessment of structural fragility in a mixed climate. Two surrogate models, Kriging and polynomial chaos expansions (PCE), are applied in this framework. Comparison with the direct MC method shows that the Kriging model rather than the PCE model is the proper surrogate model, and the surrogate model contributes significantly to saving computing time from 17 h to 1 min for MC simulations.It is also observed that uncertainties propagated from structural parameters to responses will be more notable as the wind speed increase. Buffeting fragility curves of this bridge show that it’s easier for responses in acceleration to achieve and exceed thresholds, indicating that performance related to user comfort might not be satisfied. By introducing the probability distributions of non-typhoon and typhoon winds at the site of the bridge, it is found that considering single climate may underestimate structural risk. The framework based on surrogate models in this paper can be further generalized to additional PBWE frameworks addressing different wind and structural engineering issues.

Feasibility of typhoon models and wind power spectra on response analysis of parked wind turbines

Typhoon may induce severe damages to wind turbines in both eyewall and outer vortex regions, and accurate typhoon simulation is important for the wind turbine response estimation. In this research, wind fields in these two regions are reproduced by applying two-dimensional or three-dimensional models for mean wind speed, and von Karman spectrum or Kaimal spectrum for the fluctuating wind speed. Typhoon-induced responses of parked wind turbines are calculated through time-domain analysis. The results show that three-dimensional model excels in reproducing typhoon wind field, especially for supergradient wind. Mean responses of blade and tower are underestimated with two-dimensional model in eyewall region by 8∼24%, although these differences become negligible in the outer vortex region. When taking the extreme responses with the measured spectrum as the benchmark, von Karman spectrum gives a conservative estimate for both blade and tower, while Kaimal spectrum underestimates blade by 18∼24% in the eyewall and 6∼20% in the outer vortex region, respectively. Consequently, it is recommended to apply three-dimensional model for mean response estimation of wind turbines in the eyewall region, two-dimensional model in the outer vortex region for less computation time, and von Karman spectrum for the extreme response in the whole typhoon field.

An analytic model of typhoon wind field and simulation of storm tides

Storm tides have intensified due to global climate warming, with limited attention given to storm current velocity (SCV) due to data scarcity during hurricanes/typhoons and limitations in existing wind models’ accuracy. We propose an analytic model incorporating sea-surface resistance into the gradient wind equation, offering a theoretically robust approach. Through rigorous verification against measured data, our model demonstrates significant accuracy improvement compared to established models. Simulating storm tides during Typhoon Rammasun using our approach reveals strong agreement between calculated SCVs and measured data, surpassing the performance of the Holland model. Notably, typhoon storm surges primarily respond to pressure, while SCVs are predominantly governed by wind speed in open sea. The highest water level aligns with the lowest pressure, with maximum SCVs trailing the maximum wind radius. SCVs significantly exceed astronomical tidal current velocities (ACVs) in the open sea, reaching a maximum of 3.57 m/s. Areas where the SCV-to-ACV ratio exceeds 3 constitute 21.4% of the study area. Combining our wind model with Typhoon SCV simulations provides valuable insights into storm tide dynamics, advancing our understanding of storm tide mechanisms and informing mitigation strategies.

Assessment and Integration of ERA5 Reanalysis and Fujita−Takahashi Models for Storm Surge Prediction in the East China Sea

With global climate warming, the frequency and intensity of typhoons are increasing, highlighting the significance of studying storm surges for coastal engineering disaster mitigation. In this study, we assessed the predictive capabilities of the new ERA5 reanalysis model and the traditional Fujita−Takahashi model for storm surges. We found that the traditional Fujita−Takahashi model, utilizing a prelandfall typhoon wind field, exhibited higher accuracy in storm surge predictions, while the ERA5 reanalysis model, employing a postlandfall wind field, demonstrated superior performance. By considering the strengths and weaknesses of both wind field models and analyzing the impact of Typhoon In-fa (2021) on the East China Sea, we determined the influence of this typhoon on storm surge heights along the eastern coastal region. These research findings provide valuable insights for the development of effective protection strategies, offering valuable references for coastal resilience planning.

The Impact of Observed Drag Reduction Over Land on Typhoon Forecasting

AbstractThe surface drag coefficient plays a crucial role in determining the momentum exchange between the Earth's surface and the atmosphere. Previous studies have observed a tendency for the drag coefficient to decrease at high wind speeds over land, primarily due to the inverse energy cascade. This study aims to examine the impacts of the reduced drag coefficient on the typhoon forecasting skills in terms of the track, the central pressure, and the 10‐m maximum wind speed. Drag reduction is approached through the logarithmic wind profile and a new formula that considers the reduction in roughness length. The results show that the track and the 10‐m maximum wind speed forecasts are improved, but these improvements are primarily evident over plain areas, as the typhoon structure is significantly disrupted by the topography over mountainous areas. Additionally, the reduced drag coefficient results in less dissipation of the typhoon's wind fields over land. As the wind speeds at coastal areas are enhanced compared with those in operational model, the changes in the Coriolis force are responsible for the track prediction improvement. These findings highlight the importance of parameterizing coherent processes in current numerical models.

Elucidating the impacts of trees on landslide initiation throughout a typhoon: Preferential infiltration, wind load and root reinforcement

AbstractTyphoon‐induced landslides are widespread, damaging and deadly. In this study, we elucidated their spatiotemporal features through investigations in Southeast coastal China and proposed a numerical model that involves typhoon wind load, preferential infiltration and root reinforcement. The wind load is calculated through a combination of the autoregressive method and a multi‐degree‐of‐freedom tree swaying mode, transmitting to the slope through the wind–tree interaction. Taproots of trees are modelled as piles, and root–soil interfaces are modelled as preferential infiltration boundaries. Using the numerical model, we quantitatively assessed the impacts of wind load, rainfall infiltration and root reinforcement on the slope stability and compared results with cases in Waipaoa and Wairoa (New Zealand). Results suggest that the impacts of trees depend heavily on meteorological and geological conditions. Trees play a destabilizing role in Southeast China during a typhoon but a stabilizing role in the cases in New Zealand. For slopes in Southeast China with a thick soil layer (>root depth), strong wind load and preferential flow resulting from root–soil interfaces, rather than slope surface infiltration, significantly decrease the slope stability in a short time. Slope failure occurred in all scenarios that account for the preferential infiltration, and its combination with a Force 14 typhoon wind load can fail the slope at 10 h after the typhoon initiation. Differently, tree roots in cases in New Zealand can penetrate through the thin soil layer (<1 m) and provide considerable additional resistance to stabilize the slope.

Enhanced upper ocean response within a warm eddy to Typhoon Nakri (2019) during the sudden-turning stage

The passage of typhoons usually induces a pronounced upper ocean response that is not only determined by typhoon attributes but also modulated by pre-existing mesoscale eddies. Here we examined the upper ocean response to Typhoon Nakri (2019) in the South China Sea, which first passed over a cold eddy following a straight path and then made a sudden turning over a warm eddy, on the basis of satellite observations and HYbrid Coordinate Ocean Model (HYCOM) reanalysis datasets in addition with numerical experiments. Two cold and salty patches with remarkable sea surface temperature (SST) cooling and sea surface salinity (SSS) increase emerged after Typhoon Nakri's passage in the pre-existing cold-eddy and warm-eddy regions. Particularly, the maximum SST cooling and SSS increase induced by Typhoon Nakri reached 6.6 °C and 1.6 psμ in the pre-existing warm-eddy region, which were even more pronounced than those in the pre-existing cold-eddy region (6.0 °C and 1.3 psμ). Typhoon Nakri enlarged the cold eddy and weakened the warm eddy significantly, with the maximum sea surface height reduction (up to 43 cm) appearing in the pre-existing warm eddy, which even disappeared after Nakri. Furthermore, Nakri induced phytoplankton blooms with a chlorophyll-a concentration increase reaching 2 mg m−3. The subsurface temperature (salinity) was also reduced (increased) significantly in the pre-existing warm-eddy region. The more pronounced ocean response in the warm-eddy region was largely attributed to the sudden turning of Nakri's track, prolonging the forcing time of typhoon winds. By employing the three-dimensional Price–Weller–Pinkel model, the results of numerical experiments demonstrated that typhoon's track turning as well as the accompanied slow translation speed during Nakri's sudden-turning stage, played a predominate role in resulting in the remarkable SST cooling within the warm-eddy region. These results highlight the important role of sudden track turning in modulating the upper ocean response to typhoons.

Study on the Application of Typhoon Experience Parameter Analysis in Taiwan’s Offshore Wind Farms

Due to the rapid development of computers, researchers have made efforts since the 1990s to develop typhoon forecasting models and stochastic typhoon simulation models to assess typhoon disasters and risks. Typhoon forecasting models are primarily used to predict and track the movement of typhoons and provide warning information to the general public before landfall. Stochastic typhoon simulation models can assess extreme wind speeds and compensate for the limitations of current observations and simulation data length. Taiwan experiences approximately three to four typhoons yearly, of varying intensities and paths. Whether the marine meteorological data includes events of strong typhoon centers passing through will affect the results of frequency analysis. The development of offshore wind power in Taiwan is closely related to the unique marine meteorological conditions throughout the lifecycle stages, including wind farm site selection, feasibility studies, planning and design, construction and installation, operation and maintenance, and decommissioning. This study references relevant research and analyzes sixty-three scenarios using nine types of maximum storm wind speed radii and seven Holland-B parameters. The data from Japan Meteorological Agency Best Track Data (JMA BTD) is utilized, explicitly selecting 20 typhoon events after 2000 for wind speed simulation using a typhoon wind speed model. After validating the typhoon wind speeds with observation data from the Central Weather Bureau (CWB) in Hsinchu and the Longdong buoy, the technique of Monte Carlo simulation is utilized to generate synthetic typhoons randomly. The average of the relative absolute errors for the simulated maximum wind speeds is calculated, and through comprehensive evaluation, optimal parameter combinations (Rm, B) are obtained.

Study of the Response of Environmental Factors of the Coastal Area in Zhoushan Fishery to Typhoon In-fa Based on Remote Sensing

The response of typical environmental factors in Zhoushan Fishery, including sea surface temperature (SST), sea surface salinity (SSS), and chlorophyll a (Chl-a), before and after Typhoon In-fa was analyzed using satellite data and reanalysis data in this study. Additionally, this study simultaneously elucidated the mechanism by which the typhoon affected these factors. The results showed that: (1) the strong vertical mixing caused by In-fa provoked a decrease in SST, while the asymmetric typhoon wind stress and vertical difference in temperature structure before the typhoon caused a more robust cooling of SST on the right side of the In-fa track; (2) despite the strong mixing and inflow of hypersaline seawater increasing SSS, the combined effect of intense rainfall and diluted water inflow caused an overall decrease in SSS after In-fa’s landing; (3) In-fa caused the Chl-a concentration to decrease first and then increase. The high cloudiness and low Chl-a seawater inflow inhibited the phytoplankton growth during the typhoon, while the abundant light, rich surface nutrients under the upwelling effect, and transport of rich land-based substances induced rapid phytoplankton reproduction after the typhoon; and (4) the change in Chl-a concentration, current, temperature, and salinity induced by a typhoon are essential factors that affect fish behavior and community composition in fisheries. This study provides a point of reference to reveal the response of environmental factors to typhoons and their effects on fishery resources in fisheries located on nearshore estuarine shallow waters with intensive islands.

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.

Abnormal high tides and flooding induced by the internal surge in Hiroshima Bay due to a remote typhoon

The Itsukushima Shrine is located in northern Hiroshima Bay in the Seto Inland Sea (SIS). This structure of great cultural value is preserved as one of the World Heritage Sites in Japan. The shrine was built seaside, 30 cm above the highest tide, to prevent it from submerging. However, from 2011 to 2019, the shrine was submerged four times during September due to internal surges. To study the abnormal tide event on 29 September 2011, a high-resolution numerical ocean circulation model was established using Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM). Observed subtidal components of surface elevation in the northern part of the bay decreased due to northerly winds when the typhoon passed east off the bay. After 7–8 days of typhoon passage, the component increased abnormally in the northern part of the bay. Simulation results revealed that a destabilized density stratification by the typhoon winds most likely caused bay-scale internal waves. The internal wave developed after the typhoon passed and was caught from the kinetic energy filtered in the possible internal wave periods. The internal wave propagated southward after the typhoon passage and returned to the northern bay, causing the subtidal component to increase after 7–8 days. Sensitivity tests with various scales of the typhoon were performed, and the test results exhibited a positive relationship between the abnormal tide level and typhoon intensity to some extent. The results can be generally applied to a semi-closed bay or closed water body for internal wave generation and propagation under specific meteorological conditions for coastal protection and disaster prevention.

The Typhoon Wind Hazard Assessment Considering the Correlation among the Key Random Variables Using the Copula Method

The Typhoon Wind Hazard Assessment Considering the Correlation among the Key Random Variables Using the Copula Method

Risk map of typhoon induced wave fields around Hainan Island

Typhoon is one of the major natural disasters impacting Hainan Island, and it is often accompanied by other disaster phenomena such as storm surges and high wind waves, which in turn pose a great threat to human lives and assets. In this paper, the Holland typhoon model and the Miyazaki Masae wind field model are adopted to simulate the typhoon-induced wind field for Hainan Island oceans. The hybrid wind field is established by the parametric wind field and the ERA5 reanalysis wind field. The ADCIRC+SWAN coupled model is used to simulate the typhoon wind and wave interactions, and the results reveal that the hybrid wind field model performed well compared to the measured values. Finally, based on the typhoon best-track archive from China Meteorological Administration (CMA), the risks in ocean around Hainan Island are categorized. The hybrid wind field and the ADCIRC+SWAN model is used to establish the risk map for typhoon induced wave fields, considering different typhoon tracks and seasons.

Storm Surge Inundation Modulated by Typhoon Intensities and Tracks: Simulations Using the Regional Ocean Modeling System (ROMS)

Storm surges are one of the most severe marine hazards, causing fatalities and devastating infrastructure. It is important to conduct research on storm surge hazards to achieve disaster avoidance and the protection of local populations. In this study, the Regional Ocean Modeling System (ROMS) was used to develop a framework to simulate the inundation (using the wet/dry method) of land in Ningbo, China during an extreme typhoon storm surge. The baseline simulation with the realistic typhoon intensity and track was well validated by meteorological and ocean tidal observations. Using reanalysis and an asymmetric typhoon wind field from the Holland model as atmospheric forcing, we presented different storm surge inundation scenarios regarding various intensities and tracks. The results revealed that typhoon storm surges are significantly affected by both the intensities and tracks of typhoons. Specifically, when Ningbo was located in the navigable semicircle, increasing the typhoon intensity not only resulted in the total inundation area of the whole study area from 108.57 km2 to 139.97 km2, but also led to significant negative storm surges in some sea areas. When Ningbo was exposed to the dangerous semicircle of the intensified typhoon, the storm surge along the coast of the Xiangshan Bay could exceed 4 m, amplifying the total inundation area to 245.41 km2. Thus, it was evident that the location of the impacted region within the typhoon’s wind field plays a critical role in determining the severity of the storm surge. These results provide valuable suggestions for storm surge disaster prevention and mitigation for local governments.

The Effect of Storm Surge on Three-dimensional Tidal Current Characteristics: A Case Study of “Lekima”

This study simulated the process of storm surge in the Eastern China Sea (ECS) during typhoon Lekima, based on the MIKE3 wind-surge model driven by the reconstructed typhoon wind field, which was calculated by the Holland empirical formula. The results show that, affected by shoreline and topography, the storm surge in the Hangzhou Bay and the Taizhou Bay can be more than 3.0 m during typhoon Lekima. During the typhoon, the maximum storm surge on the right side of the track was relatively larger than that on the left side, especially along the coast. And the value of maximum current speed was more than 2.5 m/s, which can be obtained in the coast of Zhejiang. The storm current speed at stations presented logarithmic distribution along the depth generally, either the astronomical tide or storm tide. The vertical structure of current velocity responded to typhoon Lekima presented obvious layered distribution. The value of current speed inner the layers was more than that in the side of the layer.

An Investigation of Impacts of Surface Waves-Induced Mixing on the Upper Ocean under Typhoon Megi (2010)

Surface waves play an essential role in regulating the mixing processes in the upper ocean boundary, and then directly affect the air–sea exchange of mass and energy, which is important for the intensity prediction of tropical cyclones (TCs). The relative and integrated impacts of the wave breaking (WB) and the wave orbital motion (WOM) on the mixing and ocean response to TC forcing are investigated under typhoon Megi (2010), using the modeled data from a fully coupled air–sea–wave model. It is shown that the WOM can effectively increase the turbulence mixing in the upper ocean, thus significantly deepening the mixing layer depth and cooling the sea surface temperature. The WB can modulate the mixing layer depth and sea surface temperature to some extent in the cold tail zone with a shallow mixing layer (owing to typhoon forcing), whereas the WOM plays a predominant role. On the aspect of ocean currents driven by typhoon winds, the WOM-induced mixing significantly weakens the current velocity and shear strength in the upper ocean mixing layer, while the relative contribution for turbulence production between the WOM and the current shear differs at different vertical regions. Moreover, the effect of the WOM on the upper ocean turbulent mixing are dependent on the location with respect to the typhoon center, the local vertical thermal structure, and surface wave states.

Comparative study of typhoon wind hazard estimation in coastal region of China using different wind field parameter models

Radius to maximum wind speed (Rmax) and Holland pressure profile parameter (B) are two key parameters for parametric typhoon or hurricane wind field modelling and hazard estimation. They are difficult to be observed or estimated for all historical storms and therefore always unavailable in most best track datasets. The statistical models were developed to correlate these two parameters with other available parameters based on limited real observation data and widely employed in typhoon hazard estimation. The applicability of these models to different ocean regions remains questionable. In this study, series of statistical models of Rmax and B are revisited and classified based on their regions of application, i.e., Gulf of Mexico and Atlantic Basin (GM&AB), South Pacific (SP), Bay of Bengal (BB) and Western North Pacific (WNP, 0°N-60°N, 100°E−180°E). Moreover, recursive models of Rmax and B in WNP are also introduced. The comparison of variation characteristics of different models for these two key parameters along with the change of typhoon surface central pressure deficit ΔPs are conducted. The stochastic typhoon tracking and intensity models are then coupled with an analytical wind field model to estimate the typhoon wind hazard of five coastal cities of China. The probability of exceedance and return period curves of wind speed are compared using different Rmax and B parameter models. The use of different Rmax and B models is shown to have significant effects on wind hazard curves. The extreme wind speeds estimated using parameter models from GM&AB and wind field model in this study are almost consistent with each other. Different models in WNP produce significant differences of wind hazard curve. The new findings in this study provide a forward step to the rational estimation of typhoon wind hazard in WNP by using the appropriate wind field parameter models.

Hindcasting and predicting surge heights and waves on the Taiwan coast using a hybrid typhoon wind and tide-surge-wave coupled model

The tide-surge-wave coupled model and hybrid typhoon wind model were developed for the Taiwan coast and employed to predict surge heights and waves under different influential factors during historical typhoon events. The results revealed that the hybrid wind model matched the measured atmospheric pressure and wind speed time series during Typhoon Soudelor (2015) and Typhoon Nesat (2017). Afterward, the measured water level, wave height, and wave period time series at different measuring stations were used to validate the tide-surge-wave coupled model. The coupled model reasonably reproduced the measured data. Subsequently, the validated model was utilized to explore the influence of the radius of maximum wind (RMW), forward speed, atmospheric pressure, wind intensity, and typhoon path on surge height, wave height, and wave setup. The results with model prediction indicate that increasing the RMW causes an increasing negative surge height and wave height and shifts the time of the peak positive surge height and peak wave height. A smaller forward speed results in a larger positive peak surge height and peak wave height at most stations. The maximum ratio changes in negative peak surge height compared with the baseline condition with Typhoon Soudelor (2015) are 105.4% and −116.0% for increasing and decreasing 20 hPa atmospheric pressures at the Linshanbi station, respectively. The differences in maximum peak wave height (ratio change) for an increasing and decreasing 10 m/s wind speed are 6.44 m (47.2%) and −5.80 m (−42.4%), respectively. The predicted results indicate that the difference in the maximum peak positive surge height (maximum ratio change) compared with the baseline condition is 1.1 m (315.2%), thereby shifting the typhoon track to the north by 100 km at the Waipu station.

Application of Radar Radial Velocity Data Assimilation in the Forecasts of Typhoon Linfa Based on Different Horizontal Length Scale Factors

In order to explore the improvement of radar radial velocity data assimilation on the initial and forecast fields of typhoons, this study assimilates the quality-controlled radial velocity data in the case of Typhoon Linfa (2015) using the three-dimensional variational data assimilation system of the weather research and forecasting model (WRF-3DVAR), and then conducts several sensitivity experiments with different horizontal length scale factors. The results show that reducing the horizontal length scale factor of the background error covariance can effectively assimilate the micro- and meso-scale information from radar data and improve the forecasting effect of Linfa. Following the optimization of the horizontal length scale factor, the radial velocity data assimilation can improve the typhoon wind field structure, produce reasonable cyclonic wind field increments, and further improve the dynamic and thermal structure of the inner core area of the typhoon. Then, we can obtain a better initial field of model forecasting, and thus typhoon track and intensity forecasting are improved.

Analysis of Dynamic Response and Current-Carrying Capacity of Bridge-along Cable under Typhoon Load

In order to study the structural dynamic response and dynamic load capacity of bridge-along cable under typhoon load, in this paper, the cable under two laying environments, including the steel box girder and steel platform, are taken as the research object. Shiyuan typhoon spectrum and harmonic superposition method are adopted to obtain the wind speed time history curves corresponding to different scales of typhoon wind force, then the wind-induced pulsating displacement of steel box girder and steel platform is calculated by using the wind speed time history curve. The electromagnetic-thermal-structure coupling model is established, and the obtained pulsating displacement under typhoon load is applied to the cable as a boundary condition to obtain its dynamic response characteristics. The eccentricity of XLPE insulation is used as the evaluation index of the current-carrying capacity of cable under different scales of typhoon wind force and different laying environments. The simulation results show that the maximum stress amplitude on the metal layer occurs near the clamp during cables are forced to move under typhoon load. The higher the typhoon wind force, the lower the allowable current-carrying capacity. Under wind force 10, the current-carrying capacity is not affected by the typhoon weather; under wind force 11, the current-carrying capacity dropped by 17.2%; under wind force 12, the current-carrying capacity dropped by 47.7%; under wind force 13, the cables are not recommended to work. The research results provide theoretical guidance for assessing the power supply reliability of bridge-along cables under typhoon disasters.