Super Typhoon Research Articles

Dynamic behavior monitoring of twin supertall buildings during Super Typhoon Soksuri using social sensing data

This paper presents the dynamic behavior monitoring of the 300-m-tall Xiamen twin towers during Super Typhoon Soksuri by means of social sensing, which involves two individuals equipped with six smart devices to conduct acceleration measurement and video footage filming. The measured acceleration data are first corrected by the resampling technique since the sampling rate of smart-device-based measurement is unstable, and the corrected building acceleration obtained from different smart devices shows good consistency. Based on the corrected building acceleration responses, the amplitude-dependent and time-variant structural dynamic properties of the monitored twin towers are revealed by the random decrement technique and the Bayesian spectral density approach, respectively. The determined structural dynamic properties are further compared with seven existing prediction models to evaluate their accuracy. Moreover, by employing a computer-vision technique (i.e., the Kanade-Lucas-Tomasi optical-flow approach), the structural dynamic displacement was extracted from the video footage filmed during Soksuri, and its accuracy was further validated through comparison with direct acceleration measurements. This paper aims to demonstrate the feasibility and effectiveness of social sensing for dynamic behavior monitoring of supertall buildings.

Precipitation Simulation and Dynamic Response of a Transmission Line Subject to Wind-Driven Rain during Super Typhoon Lekima

Typhoons bring great damages to transmission line systems located in coastal areas. Strong wind and extreme precipitation are the main sources of damaging effects. Transmission lines suffered from wind-driven rain exhibit more susceptibility to damage due to the coupled effect of wind and rainwater. This paper presents an integrated numerical simulation framework based on mesoscale WRF model, multiphase CFD model and FEM model to analyze the motions of a transmission line subjected to coupled wind and rain loads during typhoon events. A full-scale transmission line in Zhoushan Island is employed to demonstrate the effectiveness of the proposed framework by simulating typhoon evolution in terms of wind fields and rainfall, solving the coupled wind and rain fields around the conductor and predicting the dynamic responses of the transmission line during Super Typhoon Lekima in 2019. The results show that the horizontal displacements of the transmission line under the joint actions of wind and rain increase approximately 17–18% compared to those of wind loads only. It is important to consider the coupled effects of wind-driven rain on conductors in the design of transmission lines under typhoon conditions.

Impacts of Assimilating All‐Sky FY‐4A AGRI Satellite Infrared Radiances on the Prediction of Super Typhoon In‐Fa During the Period With Abnormal Changes

AbstractThe capabilities of assimilating the all‐sky Fengyun‐4A Advanced Geostationary Radiation Imager (AGRI) infrared radiances (IR) are completed by including hydrometers in the observation operator, its adjoint, and tangent linear model. This allows the three‐dimensional variational data assimilation model to include cloud‐precipitation information from infrared IR observations. Advanced as the all‐sky data assimilation methodologies are, the assimilation of cloudy scene IR radiances for tropical cyclone (TC) systems has not led to consistently better results, especially for the intensity of TCs. This work explores the effects of all‐sky AGRI radiance assimilation on a Super Typhoon In‐Fa (2106) during its stage experiencing abnormal changes in the intensity and the track. It is shown that the all‐sky assimilation of AGRI two channels 9–10 brings no obviously better TC forecasts than the all‐sky AGRI single‐channel assimilation does. Besides, the O − B (observation minus background) bias was corrected to be even larger with the variational bias correction method for the pixels with relatively lower or higher cloud impact. This indicates that traditional bias correction schemes with linear fitting functions are suboptimal if the relations between the predictor and O − B biases are non‐linear. When the conventional observation and IR radiances are assimilated in two steps, the wind in the inner‐core region is better described to properly capture the changes in the typhoon intensity. Generally, the analyses and forecasts of Typhoon In‐Fa from experiments with the all‐sky IR observations are enhanced compared to those with only the clear‐sky IR observations.

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.

Marine aquaculture spatial planning on market orientation for Pacific oyster in Shandong, China

Accessing the production value is essential to the selection of suitable sites for aquaculture farms. This study employed a Dynamic Energy Budget (DEB) model and used market-oriented indicators, including shell length, flesh weight, condition index and minimum farming duration, to analyze the suitability for Pacific oyster aquaculture in offshore Shandong, China. Chlorophyll a (Chl-a) concentration, Total Suspended Sediment (TSS) concentration, and Sea Surface Temperature (SST) were extracted by remote sensing and used as forcing variables in the bioenergetic model. Four market-oriented indicators and five zones in the study area were chosen to develop a Suitable Market-Aquaculture site-selection model (SMASM) and estimate the oyster farming suitability. The results demonstrated that Sanggou Bay exhibits high potential for Pacific oyster year-round aquaculture. Eastern Laizhou Bay is suitable for the autumn-spring fattening culture of adult oysters. Laoshan Bay and Changshan Islands are suitable for promoting rapid growth in juvenile oysters. The results of our model were consistent with the oyster production value in Shandong, showing an overall increasing trend except for the anomalous value observed in 2019. Sudden drops in water temperature, red tides, and significant increases in turbidity can exert detrimental effects on oyster production, which has been evidenced to be influenced by Super Typhoon Lekima in 2019. Although this study concentrated on a specific geographical region, the model could be applied to other regions to develop market-oriented suitability management for species and environments worldwide.

Large eddy simulation of wind pressures on a 600-m-high skyscraper and comparison with field measurements during super typhoon mangkhut

Super Typhoon Mangkhut struck the coastal cities in Southeast China on September 16, 2018, destroying many glass curtain walls of tall buildings. It calls for more investigations of the wind loads on tall buildings during strong tropical cyclones to reduce building damages. Following the field measurements of wind effects on a 600-m-high skyscraper in Shenzhen, China, during Super Typhoon Mangkhut, this study aims to reproduce the wind effects on the supertall building during Mangkhut by large eddy simulation (LES). A wide range of surrounding buildings from the target supertall building (within a radius of 5 km) is explicitly constructed for the LES. The wind profiles obtained from a 356-m-high meteorological tower in Shenzhen and those given in the local design load code are used to set the inflow conditions in the LES. The wind pressures on the supertall building simulated by the LES and monitored by the field measurements are compared and analysed, including their mean, root mean square, peak, probability density function, power spectral density, and correlation. This combined study of numerical simulation and field measurement is an impetus to promote the role of computational fluid dynamics in predictions of the wind effects on high-rise buildings under extreme wind conditions.

Forecasting Super Typhoon Saola and its effects on Hong Kong

AbstractHong Kong was severely impacted by Super Typhoon Saola (2309), necessitating the issuance of the highest tropical cyclone warning signal. Saola skirted past the south‐southwest of Hong Kong, bringing hurricane force winds and significant storm surge. Saola had its closest approach to Hong Kong on 1 September 2023, posing a unique challenge in forecasting and early warning for the start of the new school term, where higher impact to traffic and public safety was anticipated. This paper covers the challenges on the forecasting aspect of the super typhoon.

Observational study of Super Typhoon Saola in 2023 when it was close to Hong Kong

AbstractSuper Typhoon Saola came very close to Hong Kong on 1/2 September 2023, necessitating the issuance of the No. 10 hurricane signal, the highest tropical cyclone warning signal in Hong Kong. While there was widespread damage in Hong Kong, no people were killed in the event with effective early warning. It is rare that a super typhoon comes very close to Hong Kong, and this paper is a part in the series of the documentation of Saola to summarize the interesting observations of Saola near Hong Kong for future reference by weather forecasters.

The Wind Profile Characteristics of Super Typhoon Lekima Based on Field Measurement

Many cities in coastal areas are prone to typhoon disasters due to their location on the Pacific storm path, and the direct effect of catastrophic winds can lead to the destruction of low-rise buildings and severe damage to high-rise structures. The purpose of this study was to enhance the understanding of boundary layer wind profiles of strong typhoons in coastal areas and reduce property losses and casualties caused by wind disasters. Based on the field measurements of wind profile acoustic radar in coastal areas, the variation characteristics of the boundary layer wind profile during the passage of super typhoon Lekima were first studied in depth, and the evolution law of the typhoon boundary layer profile was summarized. Then, the effects of typhoon horizontal structure, topography, wind speed, and time distance on the characteristics of the typhoon profile were discussed, respectively. Finally, the evolution characteristics of wind profile parameters were obtained by fitting three wind profile theoretical models. Due to the strong variability of typhoon profile morphology, the theoretical model of wind profile is only applicable to the wind profile from the bottom to the low-level jet height of typhoons, while wind parameters are closely related to the spatial location of the typhoon wind field.

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.

Typhoon Guard: Windows Protection System for Typhoon

Typhoons are hazard that is threatening the Philippines every year. Design and construction of the houses and shelter in Catanduanes changes rapidly incorporating provision against wind speed. The effect of typhoon become the basis in the design of structures and the windows components. The study sought to answer what is the type of house built in Catanduanes, what is typical window system used for houses/building in Catanduanes, what are the protection and provision being implemented to withstand the effect of high winds pressure, and what are the safety practices to counter the effect of high winds of typhoon? Most designs and houses constructed in the late 80’s already introduced these provisions that make them easy to install the windows shutter locally termed as “typhoon guard”. This was also implemented by architects, engineers, and owners as a mandatory inclusion in the building construction and design. The selection criteria for designer and owner include the budget, structural integrity of the window, and aesthetical appearance. Respondents acknowledge that windows must be protected from the force of gusty winds and debris impact and this will also ensure that your entire house or building stays safe and intact. Many respondents agree that it is vital to protect the window from breakage by using materials that can withstand the full force of the wind pressure or employing protection components to keep the window intact and safe. However, most owners of nipa hut and a handful of owners of bungalow houses suffer minor and major damages during super typhoon Rolly, and they have common concerns about their safety and evacuation to safe buildings is the ultimate safety practice to mitigate the risk pose by the typhoon. It is recommended that typical windows systems to be used in homes and buildings must be rigid enough to withstand wind forces. Safety practices to counter the effect of high winds of typhoon includes removal of possible debris and projectile must be practiced. Also, Integrated windows protection design such as windbreaker must be re-integrated into the design of the building and adopt new window design to mitigate typhoon wind forces.

Posttraumatic stress disorder and spousal relationships in natural disaster victims: a longitudinal study

Background Posttraumatic stress disorder (PTSD) symptoms after natural disaster can have a detrimental effect on marital relationships, which may be through parenting-related factor. Aims The study aimed to examine the mechanism underlying the long-term effects of PTSD symptoms on marital satisfaction via coparenting, and its differences between men and women following the Super Typhoon Lekima. Methods Participants were 465 married victims with children. They reported their PTSD, coparenting, and marital satisfaction at three and fifteen months after the tropical cyclone. Results The results showed that for women, only higher negative cognitive and emotional alterations (NCEA) symptoms were associated with lower marital satisfaction through conflict coparenting. For men, higher intrusion, NCEA, and hyperarousal symptoms were associated with marital satisfaction through different coparenting. To be specific, for men, higher intrusion symptoms were associated with lower marital satisfaction via less reprimand coparenting; higher NCEA symptoms were associated with lower marital satisfaction via less integrity coparenting, and associated with higher marital satisfaction via less conflict coparenting; higher hyperarousal symptoms were associated with lower marital satisfaction via more conflict coparenting. Conclusions These findings suggested that the long-term effect of PTSD symptoms on marital satisfaction via coparenting mainly showed for men.

Bayesian typhoon precipitation prediction with a mixture of ensemble forecast-based and historical event-based prediction functions

Statistical post-processing has been widely adopted in probabilistic forecasting, especially when a predictive distribution of weather variables is of interest. Among the available post-processing methods, a common tool is the ensemble Bayesian model averaging. Challenges arise when it is applied to heavy rain prediction, including the precipitation produced by tropical cyclones. The issues are related to the rare extreme event and limited available data for model training. To address this, we propose in this research a Bayesian mixture model, Bmix, based on information from forecast members and historical tropical cyclones, rather than solely on immediately observed precipitation data. This approach provides a grid-specific Bayesian predictive distribution and an easy-to-derive probabilistic forecast with posterior samples generated from the Markov chain Monte Carlo algorithm. This post-processing procedure can be executed on each grid simultaneously, reducing the computational time significantly. In addition, a categorized Bmix (C.Bmix) is implemented to accommodate different scenarios such as heavy or torrential rain in applications. The proposed approaches are demonstrated on the 24-hour accumulated precipitation forecast of a category 4-equivalent super typhoon Dujuan landing in Taiwan in 2015; while two others, Matmo and Soudelor, are adopted to provide historical information. Over the Taiwan main island, a total of 1282 grids are considered, each with a resolution of 5 km and 20 ensemble member forecasts from the Weather Research and Forecasting Ensemble Prediction System (WEPS) at a 6-hour interval during the typhoon period. The analyses show that the proposed mixture approaches present larger percentages of positive CRPSS values than traditional BMA. For instance, at the time when Dujuan made landfall, the percentages are 92.2 % for Bmix, 95.2 % for C.Bmix, and 15.4 % for BMA when the true precipitation amount exceeds 200 mm/24 h. The proposed methods outperform in the probability prediction and the overall pattern of precipitation.

Trend of Storm Surge Induced by Typical Landfall Super Typhoons During 1975–2021 in the Eastern China Sea

Trend of Storm Surge Induced by Typical Landfall Super Typhoons During 1975–2021 in the Eastern China Sea

Displacement estimation for a high-rise building during Super Typhoon Mangkhut based on field measurements and machine learning

Knowledge of displacement responses of high-rise buildings under harsh wind excitations is essential for their wind-resistant structural design. This paper develops a machine learning model named long short-term memory (LSTM) to estimate the displacements of a 420-m-high building during Super Typhoon Mangkhut based on available field measurements. The developed model is trained and validated using the field measurements on the building during typhoon events, and the performance of the model is assessed against several evaluation criteria. Then, the trained LSTM model is employed to estimate the displacements of the skyscraper during Mangkhut. The accuracy of the estimated displacements is validated in time and frequency domains. Moreover, the background and resonant components of the estimated displacements during the extreme windstorm are analyzed. This paper aims to provide valuable reference for the wind-resistant design of high-rise buildings in tropical cyclone-prone regions.

Structure of a shallow squall line-like precipitation system observed in the Kanto Region, Japan, using Ka-band and X-band radars

Shallow convective systems occasionally cause heavy precipitation through active warm-rain processes, although the mechanism is not well understood. In this study, a shallow line-shaped precipitation (SLSP) system, which produced heavy rainfall in the Kanto Region, Japan, was investigated using Ka-band and X-band radars, in addition to a numerical weather prediction model. The SLSP system exhibited features similar to squall lines (SLs), such as rapid movement perpendicular to the line, but the echo-top height remained below the 0 °C level, despite the rainfall intensity reaching approximately 78 mm h−1. Therefore, the SLSP system was considered to be dominated by a shallow convective system that contained cloud droplets, raindrops and drizzle rather than a deep convective system that included ice particles. The Ka-band radar observed a low-level cloud deck spreading to the front side of the convective system, and low-level cloud subsequently entered the SLSP system. In addition, large amounts of water vapor were transported by a super typhoon came from the southwest of the Kanto Region. Cloud water supplied from the cloud deck and that condensed from the water vapor supplied by the typhoon were considered to play an important role in the heavy precipitation associated with the SLSP system through the accretion of raindrops. This study provides insights into the microphysical structure of SLSP systems as well as the precipitation processes.

The impact of WRF vertical resolution on the simulated thermal-dynamic structures and intensity of Typhoon Lekima

This study utilizes the Weather Research and Forecasting (WRF) to comparatively analyze the impact of three vertical grid resolution (VGR) enhancement schemes on the simulation of super typhoon Lekima under two different horizontal resolutions. The relationship between structural changes and typhoon intensity is explored from the perspective of the simulated three-dimensional thermodynamic and dynamic structure of the typhoon. The main conclusions obtained are as follows: Typhoon track simulation is not sensitive to the setting of VGR, while intensity simulation is greatly affected by it. Increasing VGR in the lower layer can enhance the simulated intensity of the typhoon, but when VGR enhancement is made in the middle layer, the simulated typhoon intensity decreases. For VGR enhancement in the upper levels, it is only when coupled with a simultaneous increase in horizontal resolution that the simulated typhoon intensity is enhanced. Different VGR enhancement schemes result in significant differences in the simulated thermodynamic and dynamic structures of the typhoon, which is a crucial factor causing variations in simulated typhoon intensity. In terms of dynamics, increasing VGR in the lower layer reduces the hydrostatic stability of the lower troposphere, which enhances convection and improves its symmetry. This leads to strengthened inflow and outflow activities of the typhoon, resulting in a stronger simulated typhoon with a tighter and straighter eyewall. In terms of thermal structure, increasing VGR in both the lower and upper levels enhances the warm core of the typhoon, thereby increasing its simulated intensity. However, the warm core simulated with upper layer enhancement extends to a higher altitude. This may be related to two different heating mechanisms, where lower layer VGR enhancement has a more pronounced effect on changes in boundary layer latent heat flux, while upper layer VGR enhancement promotes more sinking of high-entropy air from higher levels.

The North Equatorial Current and rapid intensification of super typhoons

Super Typhoon Mangkhut, which traversed the North Equatorial Current (NEC; 8–17 °N) in the western North Pacific in 2018, was the most intense Category-5 tropical cyclone (TC) with the longest duration in history—3.5 days. Here we show that the combination of two factors—high ocean heat content (OHC) and increased stratification — makes the NEC region the most favored area for a rapid intensification (RI) of super typhoons, instead of the Eddy Rich Zone (17–25 °N), which was considered the most relevant for RI occurrence. The high OHC results from a northward deepening thermocline in geostrophic balance with the westward-flowing NEC. The stratification is derived from precipitation associated with the Inter-Tropical Convergence Zone in the summer peak typhoon season. These factors, which are increasingly significant over the past four decades, impede the TC-induced sea surface cooling, thus enhancing RI of TCs and simultaneously maintaining super typhoons over the NEC region.

Assessment of typhoon disaster loss based on the factor analysis-random forest model

Typhoon disasters in China’s coastal areas pose significant challenges for disaster prevention and mitigation, urban planning and national economic construction. This study aims to address the problem of incomparable disaster assessment indicators and low prediction accuracy of machine learning for small sample data. It establishes an index system based on the practical disaster investigation classification standards, which ensures data sources and uniformity. It also proposes a combination algorithm of factor analysis-random forest regression for direct economic loss prediction, which improves the typhoon disaster losses prediction. The results show that the optimized model has higher accuracy than single decision tree model, random forest model and factor analysis-decision tree model. The factor analysis method verifies the importance of influencing factors, which indicates that China faces great risks of coastal floods caused by super typhoons. The combination regression model can predict disaster losses reasonably, providing effective technical support for typhoon disaster assessment and management.

Revisiting the Characteristics of Super Typhoon Saola (2023) Using GPM, Himawari-9 and FY-4B Satellite Data

Typhoon Saola was the ninth typhoon that generated over the Western North Pacific (WNP) in 2023, and it caused severe storm impacts. However, its complex moving track and heavy intensity made it extremely difficult to forecast; therefore, detailed analysis is necessary. In this study, GPM, Himawari-9, and FY-4B satellite data were used to analyze the characteristics of the structure, brightness temperature, and precipitation of the typhoon cloud system. Our results showed that, in the 89 and 183 GHz channels of GPM-1CGMI, the brightness temperature of the typhoon eye was 80–90 K higher than that of the eye wall, and the strong convective areas below 200 K were clearer in these high-frequency channels. GPM-2ADPR estimated heavy rain (over 30 mm/h) area, storm height (5 km), and vertical precipitation rate (30–40 mm/h) more accurately than the GPM-2Aka and GPM-2Aku products. Himawari-9 satellite data showed that the brightness temperature of the eye wall and spiral cloud bands was 180–200 K, the typhoon eye was small and round, and strong convective activities were mostly located in the southwest side of the center. The FY-4B CLP and CLT products showed that, in the mature period of the typhoon, the percentage of supercooled and mixed clouds first stabilized and then rapidly decreased. The trends observed among the three types of ice-phase clouds were characterized by an initial increase, followed by a decrease, and then another increase, with percentages between 10% and 25%, 5% and 15%, and 15% and 30%, respectively.