Super Typhoon Rammasun Research Articles

A Qualitative Study of Disaster Resilience of Chinese Adolescents Five Years after Super Typhoon Rammasun

Adolescents and younger children are more vulnerable during and after disasters than adults, and their ability to develop resilience depends on many factors, including culture and context. However, adolescents’ experiences and voices need to be considered more often in disaster research, since their understanding of disaster resilience is not known in depth. This study aimed to understand Chinese adolescents’ disaster resilience experiences five years after their exposure to the Super Typhoon Rammasun. A qualitative descriptive design was applied. As far as the researchers are aware, this was the first qualitative study in China to explore adolescents’ disaster experiences and disaster resilience. In-depth interviews were conducted in Hainan province, on an island in the South China Sea, with 30 high school adolescents exposed to Super Typhoon Rammasun. Data were collected from March to October 2019 and analyzed using content analysis.Analysis revealed rich findings and three categories emerged reflecting how the adolescents experienced disaster resilience: 1) Experiencing challenges, with three subcategories (Disrupted daily life, Loss and damage, and Negative emotions); 2) Coping and adaptive strategies, with four subcategories (Seeking support, Gaining strength from role models, Role engagement, and Self-managing); and 3) Adaptation after facing typhoon, with three subcategories (Being strong to deal with difficulty, Having good immunity, and Improved knowledge and skills in dealing with typhoons). The findings can provide understanding and inform nurses and other healthcare professionals in disaster preparation, disaster management and community resilience, as well as educators and policymakers, to support and develop disaster resilience in adolescents. Disaster resilience is enhanced by fostering interventions to help those exposed to disasters respond and recover from disaster impacts, considering culture and context. Future clinical screening and research could use the adaptive outcomes in our findings as indicators for developing long-term disaster resilience among adolescents.

Microphysical processes under different hourly rainfall intensities in super typhoon Rammasun

High-resolution numerical simulation data of super typhoon Rammasun simulated by the Weather Research and Forecasting (WRF) Model was used to study the cloud microphysical processes under different hourly rainfall intensities. The grid points in the gale circle were categorized into four types (0–5, 5–20, 20–50, and 50- mm) based on hourly rainfall. The precipitation and microphysical characteristics under different types were investigated by diagnostic and statistical methods. The results showed that on the eve of the first landfall, extremely hourly heavy precipitation (50- mm type) was significantly enhanced compared to other types. The vertical movement was significantly reduced to the middle and lower troposphere which was very conducive to the relative movement and interaction of hydrometeors with the enhancement of the collision processes. The rainfall in the 5–20 and 20–50 mm types both mostly accounted for about 40% of the total rainfall in the gale circle, while that of the 0–5 and 50- mm types were generally smaller than the former two. As the rainfall intensity increased, the absolute conversion rates of all major cloud microphysical processes had shown increasing trends, especially the non-uniformity of Cnd (the condensation of water vapor to cloud water), Pracw (the accretion of cloud water by rain) and Dgacw (the accretion of cloud water by graupel). The relative contribution of Pgmlt (the melting of graupel) increased slightly and then decreased significantly from the 20–50 mm type (36.28%) to the 50- mm type (25.06%), while that of Pracw had significantly increased especially from the 20–50 mm type (41.77%) to the 50- mm type (50.97%), which was related to the upward motion characteristics.

Influence of radiation diurnal variation on the rapid intensification process of super Typhoon Rammasun (1409) in the South China Sea

In this study, a sensitivity experiment based on a numerical model is conducted to study the influence of the diurnal variation of radiation on the rapid intensification process of Super Typhoon Rammasun (1409) in the South China Sea. The result shows that changing the radiation process can change the onset time of the rapid intensification process of the typhoon and its maximum intensity. Vertical wind shear is a key factor in the TC rapid intensification influenced by diurnal radiation cycle, and the diurnal variation of radiation process causes obvious diurnal variation in vertical wind shear by changing the thermal difference between sea and land. The oscillation of vertical wind shear promotes the diurnal variation of the typhoon rainband, with an opposite variation trend in the control and sensitivity experiments, affecting the local convective available potential energy and inward transport of entropy and thus influencing the onset time of deep convective in the typhoon inner core region. By changing the establishment of the typhoon warm core (especially the upper-level warm core), deep convections finally affect the rapid intensification of the typhoon.

Forest Damage by Super Typhoon Rammasun and Post-Disturbance Recovery Using Landsat Imagery and the Machine-Learning Method

Typhoon Rammasun landed on the southern coastal region of Guangdong and Hainan Provinces on 18 July 2014, and is the strongest recorded typhoon since the 1970s in China. It caused enormous losses in human lives, property, and crop yields in two provinces; however, its impact on forests and subsequent recovery has not yet been assessed. Here we detected forest damage area and severity from Typhoon Rammasun using Landsat 8 OLI imagery, the Random Forest (RF) machine-learning algorithm, and univariate image differencing (UID) methods, and the controlling factors on damage severity and canopy greenness recovery were further analyzed. The accuracy evaluations against sample plot data indicated that the RF approach can more accurately detect the affected forest area and damage severity than the UID-based methods, with higher overall accuracy (94%), Kappa coefficient (0.92), and regression coefficient (R2 = 0.81; p < 0.01). The affected forest area in Guangdong and Hainan was 13,556 km2 and 3914 km2, accounting for 13.8% and 18.5% total forest area, respectively. The highest affected forest fractions reached 70% in some cities or counties. The proportions of severe damage category accounted for 20.85% and 21.31% of all affected forests in Guangdong and Hainan, respectively. Our study suggests that increasing tree density and choosing less sensitive tree species would reduce damage from typhoons in vulnerable areas such as fringe, scattered, and high-slope forests. The canopy greenness of damaged forests recovered rapidly within three months for both provinces; however, management strategies should still be applied in the severely damaged areas to sustain forest functions since the persistent forest canopy structure and biomass may require a longer time to recover.

Model Simulation of Storm Surge in the Northwestern South China Sea Under the Impact of Sea Level Rise: A Case Study of Super Typhoon Rammasun (2014)

Because of global warming, the sea level is expected to continue to rise, possibly having a significant impact on the intensities and spatial distribution characteristics of coastal storm surges. In this study, we took super typhoon Rammasun (2014) as a case study and applied the SCHISM (Semi-implicit Cross-scale Hydroscience Integrated System Model) to simulate storm surge in the northwestern South China Sea under future sea level rise (SLR) scenarios. To improve the accuracy of storm surge hindcast, we used reconstructed wind field to drive the model in which ERA5 reanalysis data were superposed on the wind field calculated from the Holland parametric cyclone model. The results show that the storm surge hindcast was significantly improved by using this reconstructed wind forcing. 2-D and 3-D model hindcast capabilities were compared; the 3-D model reproduced the storm surge better. The regional sea level projections in 2050, 2100, 2200, and 2300 for RCP 4.5 scenarios (provided by the IPCC AR6 dataset) were superposed on the original water depth as the predicted sea levels, then those depths were used in models of storm surge in the study area under a typhoon identical to Rammasun. Model results demonstrate that storm surge peaks in most sea areas decrease nearly linearly with SLR, especially in regions of high surges.

Relationships between the Southwest Monsoon Surge and the Heavy Rainfall Associated with Landfalling Super Typhoon Rammasun

Based on the China Meteorological Administration (CMA) best-track data, the ERA5 reanalysis, and the Global Precipitation Measurement (GPM) precipitation data, this paper analyzes the reasons for the heavy rainfall event of Super Typhoon Rammasun in 2014, and the results are as follows: (1) Rammasun was blocked by the western Pacific subtropical high (WPSH), the continental high, and the mid-latitude westerly trough. Such a stable circulation pattern maintained the vortex circulation of Rammasun. (2) During the period of landfall, the southwest summer monsoon surge was reinforced due to the dramatic increase of the zonal wind and the cross-equatorial flow near 108° E. The results of the dynamic monsoon surge index (DMSI) and boundary water vapor budget (BWVB) show that the monsoon surge kept providing abundant water vapor for Rammasun, which led to the enhanced rainfall. (3) The East Asian monsoon manifested an obvious low-frequency oscillation with a main period of 20–40 days in the summer of 2014, which propagated northward significantly. When the low-frequency oscillation reached the extremely active phase, the monsoon surge hit the maximum and influenced the circulation of Rammasun. Meanwhile, the convergence and water vapor flux associated with the low-frequency oscillation significantly contributed to the heavy rainfall.

Fine-Scale Structures in the Mid-Level Eyewall of Super Typhoon Rammasun (2014) Simulated With the WRF-LES Framework

It has been numerically demonstrated that the turbulence above the boundary is important to tropical cyclone intensification and rapid intensification, but the three-dimensional structures of the sub-grid-scale (SGS) eddy have not been revealed due to the lack of observational data. In this study, two numerical simulations of Super Typhoon Rammasun (2014) were conducted with the Advanced Weather Research and Forecast (WRF) model by incorporating the large-eddy simulation (LES) technique, in which the enhanced eyewall convection and the process of rapid intensification are captured. Consistent with previous observational studies, the strong turbulent kinetic energy (TKE) is found throughout the whole eyewall inside of the radius of maximum wind in both experiments. The simulations indicate that the strong TKE is associated with horizontal rolls with the horizontal extent of 2–4 km, which are aligned azimuthally in the intense eyewall convection. It is indicated that the three-dimensional structures of the SGS eddy can be simulated with the vertical grid spacing of ∼100 m when the horizontal grid spacing is 74 m. It is suggested that there is considerable turbulence associated with azimuthally-aligned horizontal rolls in the mid-level eyewall of tropical cyclone.

Far-Field Impacts of a Super Typhoon on Upper Ocean Phytoplankton Dynamics

Super typhoon Rammasun (2014) traveled across the South China Sea on July 16–18. Its far-field impacts on phytoplankton dynamics in the upper ocean were documented by a Biogeochemical-Argo (BGC-Argo) float located 200 km to the left of its track. Both surface chlorophyll-a concentration (Chla) and particulate backscattering coefficient (bbp) were observed to increase substantially within two distinct stages. The initial increase occurred during the passage of the typhoon, and the subsequent increase happened 5 days after the typhoon. In contrast, depth-integrated Chla and bbp in the upper 150 m underwent negligible changes throughout the entire period. The key lies in the fact that surface phytoplankton increases in the far-field region resulted from the physically driven vertical redistribution of particles, rather than from biological alternations. The first increase was attributed to the typhoon-induced strong turbulence which deepened the surface mixed layer, and thus entrained subsurface particles to the surface; the second was due to the post-typhoon adiabatic quasi-geostrophic adjustment of the upper ocean that gradually raised the isopycnals (and thus subsurface particles). These results challenge the prevailing wisdom on typhoon impacts, and thus shed new lights on the nature of the upper ocean responses to typhoons from both physical and biological perspectives.

Strengthening effect of super typhoon Rammasun (2014) on upwelling and cold eddies in the South China Sea

Strengthening effect of super typhoon Rammasun (2014) on upwelling and cold eddies in the South China Sea

Evaluation on the Meteorological Service for Mitigating the Severe Impacts of Typhoon Rammasun

This study takes the meteorological service of super typhoon Rammasun as an example, and proposes a multi-dimensional quantitative assessment method for meteorological service. Rammasun was the strongest typhoon that landed in China from 1949 to 2019. It hit the coastal areas of China three times, with a rare landing intensity in history. Guangdong, Guangxi, Hainan, Yunnan and other provinces have suffered disasters of varying degrees, with a total affected population of 12.084 million and a direct economic loss of 44.89 billion CNY. During this period, the total investment in meteorological services was approximately 1.213 billion CNY, and the economic benefits of disaster prevention and mitigation in the four disaster-stricken provinces were worth 16.1 billion CNY. According to the cost-benefit analysis of economics, the input-output ratio for disaster prevention and mitigation in Typhoon Rammasun was 1:13.

Typhoon Inversion Method Combined With the YanMeng Wind Field and a Meteorological Monitoring System for Transmission Lines

Extreme weather like typhoon leaves significantly terrible influence on the stability of power grid in the coastal area. A high-voltage transmission line includes hundreds of towers and usually stretches hundreds of kilometers. It is not economical to install typhoon monitoring system throughout the transmission line. This paper proposes a typhoon inversion method (TIM) for transmission line which utilizes engineering wind field model and only requires monitoring data from a few towers. The developed method is called YanMeng wind field (YM) with directional mutation genetic algorithm (DMGA) for transmission lines, or YM-DMGA method. DMGA utilizes real-time monitoring data, and improves simulation accuracy of average wind speed by dynamically optimizing two critical parameters <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$z_{0}$ </tex-math></inline-formula> in wind field model, which is a great improvement over the traditional YM model relying on historical data. The TIM is mainly composed of three parts, the meteorological monitoring system (MMS), the YM-DMGA model, and the software system. The TIM collects real-time measured wind data of particular monitoring stations through the MMS. Meanwhile, wind data of the whole transmission line is simulated using the YM-DMGA and displayed by the software system. Then the method proposed is verified to be effective in three aspects. First of all, the YM-DMGA method has great enhancement in accuracy, for the coefficient of determination <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{square}$ </tex-math></inline-formula> increases from 0.811 to 0.986. Secondly, DMGA in the method has quicker convergent speed than typical GA, with fitness converged in the 269 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> epoch, earlier than that for typical GA, 656 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> epoch. Lastly, DMGA has better optimal fitness value of 0.6239, bigger than that of typical GA, 0.5891. At the end of the paper, an application of the method to an 110kV double-circuit transmission line is presented to reveal the risk under the impact of the super typhoon Rammasun.

A Comparative Study on the Offshore Intensification of Supertyphoon Rammasun (2014) and Typhoon Rumbia (2013): the Role of Summer Monsoon

The offshore intensification mechanisms of Supertyphoon Rammasun (2014) and Typhoon Rumbia (2013) are analyzed and compared based on the best track typhoon data provided by the Shanghai Typhoon Institute of China Meteorological Administration (STI/CMA), ECMWF (CMA and JMA) objective (subjective) predicted typhoon track and intensity, and reanalysis data of the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR). Results show that the offshore sea surface temperature over 28 °C was conducive to the intensification of the two typhoons in the coastal area prior to their landfall in South China. Rammasun was embedded in an extremely active phase of a 10–20-day oscillation in the summer monsoon over the South China Sea and western North Pacific prior to its landfall. The low-level jet transported warm and moist air to the inner core of Rammasun and the deepening of the southwesterly monsoon flow up to 200 hPa reduced vertical wind shear, both favorable for the offshore rapid intensification of Rammasun. In 2013, the summer monsoon over the South China Sea and western North Pacific experienced quasi-20-day and quasi-10-day oscillations. The out of phase of the two oscillations resulted in relatively weak tropical and subtropical summer monsoon flow prior to the landfall of Rumbia. As a result, the low-level monsoon flow transported relatively less moist air into Rumbia, and the shallow monsoon flow was not conducive to the weakening of vertical wind shear, resulting in a less rapid offshore intensification of Rumbia than Rammasun.

Analysis of an Ensemble of High-Resolution WRF Simulations for the Rapid Intensification of Super Typhoon Rammasun (2014)

Diagnostics are presented from an ensemble of high-resolution forecasts that differed markedly in their predictions of the rapid intensification (RI) of Typhoon Rammasun. We show that the basic difference stems from subtle differences in initializations of (a) 500–850-hPa environmental winds, and (b) midlevel moisture and ventilation. We then describe how these differences impact on the evolving convective organization, storm structure, and the timing of RI. As expected, ascent, diabatic heating and the secondary circulation near the inner-core are much stronger in the member that best forecasts the RI. The evolution of vortex cloudiness from this member is similar to the actual imagery, with the development of an inner cloud band wrapping inwards to form the eyewall. We present evidence that this structure, and hence the enhanced diabatic heating, is related to the tilt and associated dynamics of the developing inner-core in shear. For the most accurate ensemble member: (a) inhibition of ascent and a reduction in convection over the up-shear sector allow moistening of the boundary-layer air, which is transported to the down-shear sector to feed a developing convective asymmetry; (b) with minimal ventilation, undiluted clouds and moisture from the down-shear left quadrant are then wrapped inwards to the up-shear left quadrant to form the eyewall cloud; and (c) this process seems related to a critical down-shear tilt of the vortex from midlevels, and the vertical phase-locking of the circulation over up-shear quadrants. For the member that forecasts a much-delayed RI, these processes are inhibited by stronger vertical wind shear, initially resulting in poor vertical coherence of the circulation, lesser moisture and larger ventilation. Our analysis suggests that ensemble prediction is needed to account for the sensitivity of forecasts to a relatively narrow range of environmental wind shear, moisture and vortex inner-structure.

Changes in the hydrodynamic characteristics of the upper layer of the South China Sea during the period of super typhoon Rammasun (2014)

Severe typhoon Rammasun (2014) was strengthened (super typhoon) in the east of the Leizhou Peninsula before moving into the Beibu Gulf. This study used the empirical orthogonal function (EOF) method to analyze the spatiotemporal variations in the sea surface wind (SSW), surface level anomaly (SLA), sea surface temperature (SST), mixed layer depth (MLD) and precipitation of the SCS. The study found that this typhoon had a significant influence on the SSW, SLA, SST, MLD and precipitation changes. During the typhoon Rammasun, the spatial distribution of precipitation showed obvious ‘left-hand-side intensification’ relative to the typhoon track. However, the SST decreased rapidly, and cooling showed a clear ‘right-hand-side intensification’, and two cyclonic eddies in the southwestward were observed from the mode of EOF-1 of the SLA. The spatiotemporal variations of SST, MLD, SLA, SSW and precipitation during the period of super typhoon Rammasun were excellently reflected by the EOF method. The variabilities of SST, MLD, SLA, SSW and precipitation in the SCS during the typhoon period and the relationship between the variabilities were further analyzed.

Structural failure analysis of a river-crossing transmission line impacted by the super typhoon Rammasun

Steel lattice towers are commonly used as supporting structures for overhead transmission lines. Extreme wind conditions like typhoons can cause significant damage on those steel towers and consequently jeopardize the safe operation of transmission lines. In the line sections where a river crossing is unavoidable, the steel lattice towers are designed to be much taller and stronger than regular towers owing to safety and operation considerations. In previous typhoon events in Hainan Province of China, none of the installed river-crossing towers have collapsed or experienced significant damages, except in the aftermath of super typhoon Rammasun in 2014, when two 95-m tall river-crossing suspension towers collapsed. This paper presents the structural failure analysis of these two collapsed lattice steel transmission towers: The improved genetic algorithm (IGA) was applied to solve the typhoon wind field model for improved resolution of wind records measured during the Rammasun event and based on of 10-min average wind speeds. The IGA used the field measurement data to generate time-varying typhoon key parameters that lead to a more accurate prediction of the wind field than the conventional method. Then a systematic procedure was developed to investigate the failure mechanism of steel lattice towers under fluctuating wind loads combined with rain loads with consideration of the aerodynamic characteristics of the transmission tower-line system. The results show that the root-cause of the structural failure of the two transmission towers was overstressing of the tower main leg members in the second panel above the ground. Based on the numerical simulation of typhoon wind loads and the structural failure analysis procedure applied in this study, a general reinforcement method of river-crossing towers is proposed and the implementation of a typhoon warning method is recommended to identify the potential risks in transmission lines and formulate corresponding typhoon emergency plans to reduce the losses caused by typhoons.

Diel vertical migration of zooplankton and micronekton on the northern slope of the South China Sea observed by a moored ADCP

Acoustic Doppler current profiler (ADCP) echoes can be transformed into mean volume backscattering strength (MVBS), which is positively proportional to the biomass of zooplankton and micronekton. A mooring with an upward-looking 75-kHz ADCP was deployed on the northern slope of the South China Sea to monitor diel vertical migration (DVM) and vertical distributions of zooplankton and micronekton under general conditions and extreme conditions such as typhoons. DVM occurs throughout the year, with the maximum migrating speed reaching 9.0 cm s−1. It had some cyclic variation, which was in response to marine environment and astronomical influence. Light initiates the ascents and descents of the migrators, and migration intensity may be proportional to the solar altitude. Neap-spring tidal cycle and full moon phase influences are prominent, and the peak at 112 d may be driven by variation of currents. In addition, 270 m is the demarcation between upward and downward migrations; some organisms living below this layer, especially zooplankton and micronekton, migrate to the surface to obtain nutrients and energy; other marine mesopelagic organisms also survive in this manner. Super and severe typhoons reduced vertical migration, having less influence on the deep scattering layer. As Super Typhoon Rammasun passed by the mooring station, current speed increases and temperature decreases were synchronous with changes in the deep scattering layer; the migrators swam downward to evade the influence of a higher-speed current rather than swam upward to compensate for the decrease of temperature.

Monitoring of Near-Surface Winds and Wind Pressures on an Instrumented Low-Rise Building during Super Typhoon Rammasun

This paper presents the results of observed near-surface winds and wind-induced pressures on the gable roof of an instrumented low-rise building. The observations were made during the strongest typhoon to make landfall in China since 1949—Super Typhoon Rammasun. For comparison purposes, the paper also presents field measurements taken during four other tropical cyclones of lower strengths. This work first investigates the characteristics of near-surface winds, including those of turbulence intensities, turbulence integral length scales, gust factors, and wind turbulence spectra. The work then offers an analysis of the mean, RMS, and minimum pressure coefficients on the gable roof under oblique winds. To investigate the influences of windstorm strengths on the pressure coefficients, a comparative study is made of the measurements recorded during Super Typhoon Rammasun and those recorded during the four tropical cyclones. To explore the mechanisms of how high suctions are generated, spectral analysis is conducted for the wind pressures near the roof edges. In addition, the effects of elevation angle on the wind pressures are investigated. This study aims to shed light on the wind effects of extreme wind conditions on low-rise buildings and to provide useful information on how to improve the wind-resistant design of low-rise buildings.

Failure analysis of a lattice transmission tower collapse due to the super typhoon Rammasun in July 2014 in Hainan Province, China

The failure mechanisms of lattice transmission towers under the extreme wind conditions of typhoons are not well known and such knowledge is important for the improvement of overhead transmission line (OHL) design and to ensure the safe operation of transmission lines in typhoon-prone areas. This paper presents a case study on failure analysis of 13 collapsed lattice transmission towers in a110 kV transmission line during the super typhoon Rammasun that occurred in July 2014 in Hainan Province of China. A systematic computational procedure was developed to conduct the failure analysis with particular focus on modeling the fluctuating turbulent wind loads combined with the heavy rain loads. The results show that the failure mode and location obtained from the dynamic analysis are in good agreement with the post-event field observations. The collapse of the suspension lattice transmission towers was triggered by the buckling of the main leg members in the third panel from the ground level due to the extreme high axial stresses. Key design suggestions like improving the design wind speed and adopting an equal-strength beam approach are proposed to reduce the risk of lattice transmission tower failure and ensure continued serviceability and safe operations under the typhoon-wind conditions.

Assessing the influence of assimilating radar-observed radial winds on the simulation of a tropical cyclone

Observations by Doppler weather radar are crucial for nowcasting and short-time forecasting of severe weather events as they bring in refined information of the atmosphere. However, due to the inevitable noises and non-meteorological signals, they cannot be assimilated straightforwardly into a numerical model. In the present study, assimilation of the radial component of wind velocity observed by two Doppler radars is performed in the numerical simulation of Supertyphoon Rammasun (2014) just before its landfall. After several quality-control steps, the radar-observed radial velocities are de-aliased, noise-reduced and assimilated into the model to improve initial conditions for the high-resolution simulation. Results show that only when using global background error covariance matrix can the observational increment be properly assimilated into the model, correcting large-scale background steering flow and yielding a simulated track close to the observed one. However, little improvement is found in simulating the TC core-scale structures by the assimilation of radar velocity as compared to the radar-observed flow, primarily due to the insufficient spatial resolution of the model that may lead to the incorrect representation of the TC core structure and the rejection of some core-region observations during the data assimilation procedure. Moreover, assimilation-induced asymmetries consume a certain portion of mean kinetic energy, preventing the simulated Rammasun from axisymmetrization and thus intensification as compared with the non-assimilated experiment.

FOREST DISTURBANCE ANALYSIS WITH LANDSAT-8 OLI DATA RELATED TO A PARAMETRIC WIND FIELD: A CASE STUDY FOR TYPHOON RAMMASUN (201409)

Abstract. Forest disturbance induced by tropical cyclone often has significant and profound effects on the structure and function of forest ecosystem. Detection and analysis of post-disaster forest disturbance based on remote sensing technology has been widely applied. At present, it is necessary to conduct further quantitative analysis of the magnitude of forest disturbance with the intensity of typhoon. In this study, taking the case of super typhoon Rammasun (201409), we analysed the sensitivity of four common used remote sensing indices and explored the relationship between remote sensing index and corresponding wind speeds based on pre-and post- Landsat-8 OLI (Operational Land Imager) images and a parameterized wind field model. The results proved that NBR is the most sensitive index for the detection of forest disturbance induced by Typhoon Rammasun and the variation of NBR has a significant linear dependence relation with the simulated 3-second gust wind speed.