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1. Introduction In early September 2022, tropical cyclone (TC) Hinnamnor struck South Korea, resulting in 12 fatalities and tremendous socioeconomic damages. (1) Hinnamnor was the first super typhoon (lifetime maximum [...]

This study documents the inter-decadal change of the lagged inter-annual relationship between the TC frequency (TCF) and the local sea surface temperature (SST) in the western North Pacific (WNP) during 1979-2014. An abrupt shift of the lagged relationship between them is observed to occur in 1998. Before the shift (1979-1997), a moderately positive correlation (0.35) between previous-year local SST and TCF is found, while a significantly negative correlation (− 0.71) is found since the shift (1998-2014). The inter-decadal change of the lagged relationship between TCF and local SST over the WNP is also accompanied by an inter-decadal change in the lagged inter-annual relationship between large-scale factors affecting TCs and local SST over the WNP. During 1998-2014, the previous-year local SST shows a significant negative correlation with the mid-level moisture and a significant positive correlation with the vertical wind shear over the main development region of WNP TC genesis. Almost opposite relationships are seen during 1979-1997, with a smaller magnitude of the correlation coefficients. These changes are consistent with the changes of the lagged inter-annual relationship between upper- and lower-level winds and local SST over the WNP. Analyses further suggests that the inter-decadal shift of the lagged inter-annual relationship between WNP TCF and local SST may be closely linked to the inter-decadal change of inter-annual SST transition over the tropical central-eastern Pacific associated with the climate regime shift in the late 1990s. Details on the underlying physical process need further investigation using observations and simulations. [ABSTRACT FROM AUTHOR]

The interannual variability of typhoon onset date in western North Pacific (WNP) during 1979-2015 is investigated. The average date in the earlier (later) onset group is early April (late July). A diagnosis of the genesis potential index shows that the key factor affecting the earlier and later onset lies in the background moisture field. According to their evolution feature, the earlier onset cases are further divided into two sub-groups. In the first sub-group, positive specific humidity anomalies were confined in the western WNP and caused primarily by circulation anomalies associated with a La Niña in the equatorial eastern Pacific. In the second sub-group, positive specific humidity anomalies were confined in the eastern WNP and caused by anomalous convection associated with the Pacific Meridional Mode (PMM) in the tropical and subtropical eastern Pacific. In the later onset composite, negative specific humidity anomalies appear in the WNP, and were accompanied by an anomalous anticyclone in situ and a V-shape negative SSTA pattern in the western Pacific. In addition, the change of background vertical wind shear (VWS) also influences the TC onset date. A decrease (increase) in the VWS magnitude and an easterly (westerly) shear anomaly occur in the earlier (later) onset composite. Physically it is argued that both the magnitude of the VWS and the sign of anomalous zonal wind shear may affect TC formation in the WNP. [ABSTRACT FROM AUTHOR]

Flooding associated with landing tropical cyclones (TCs) is one of the major natural hazards in the coastal region of Vietnam. Annually, approximately 5 or 6 TCs make landfall in Vietnam, bringing heavy rains and inducing flooding, particularly to the central coastal region because of its topography and geographic configuration. This study focuses on the modelling of typhoon-induced floods that have resulted in widespread damage to agriculture over the central Thua Thien Hue Province of Vietnam by coupling two well-known hydrological models, KINEROS2 and HEC-RAS (Daniel et al. in Open Hydrol J 5(1), 2011), and using GSMaP (Global Satellite Mapping of Precipitation) data as the satellite rainfall input. Landsat imagery and GIS are also used for mapping and analysing the inundated areas. The discharge and water level from the KINEROS2 and HEC-RAS models displayed acceptable results for the floods modelled from three selected typhoons; both the Nash-Sutcliffe simulation efficiency coefficient (NSE) and the coefficient of determination (R2) were greater than 0.6. The simulated inundation maps of these typhoon-induced floods were compared with those extracted from the Landsat imagery to assess consistency. The result revealed a similar spatial extension of the inundated agricultural areas. This information, together with the forecasted TC movements and associated rainfalls, will be helpful to plan methods for mitigating potential typhoon-induced flooding and damage, particularly damage to agricultural regions. [ABSTRACT FROM AUTHOR]

The dynamics and behaviors of streamwater chemistry are rarely documented for subtropical small mountainous rivers. A 1-year detailed time series of streamwater chemistry, using non-typhoon and typhoon samples, was monitored in two watersheds, with and without cultivation, in central Taiwan. Rainwater, soil leachate, and well water were supplemented to explain the streamwater chemistry. The concentrations of fluoride, chloride, sulfate, magnesium, potassium, calcium, strontium, silicon, and barium of all the water samples were measured. Principal component analysis and residual analysis were applied to examine the mechanisms of solute transport and investigate possible sources contributing to the streamwater chemistry. In addition to the influence of well water and soil leachate on streamwater chemistry during non-typhoon period, overland flow and surface erosion affect streamwater chemistry during the typhoon period. The latter has not been discussed in previous studies. Surface erosion is likely to be an end member and non-conservatively mixed with other end members, resulting in a previously unobserved blank zone in the mixing space. This has a particularly great impact on small mountainous watersheds, which suffer from rapid erosion. Moreover, fertilizer contaminates agricultural soil, making soil water end members more identifiable. To our knowledge, this study is the first to clearly illustrate the dynamics and sources of streamwater chemistry of small mountainous rivers that are analogous to rivers in Oceania. [ABSTRACT FROM AUTHOR]

The processes leading to the rapid intensification (RI) of Typhoon Megi (2010) are explored with a convection-permitting full-physics model and a sensitivity experiment using a different microphysical scheme. It is found that the temporary active convection, gradually strengthened primary circulation, and a warm core developing at midlevels tend to serve as precursors to RI. The potential vorticity (PV) budget and Sawyer- Eliassen model are utilized to examine the causes and effects of those precursors. Results show that the secondary circulation, triggered by the latent heat associated with active convection, acts to strengthen the mid- to upper-level primary circulation by transporting the larger momentum toward the upper layers. The increased inertial stability at mid- to upper levels not only increases the heating efficiency but also prevents the warm-core structure from being disrupted by the ventilation effect. The warming above 5 km effectively lowers the surface pressure. It is identified that the strong secondary circulation helps to accomplish the midlevel warming within the eye. The results based on potential temperature (θ) budget suggest that the mean subsidence associated with detrainment of active convection is the major process contributing to the formation of a midlevel warm core. On the possible causes triggering the inner-core active convection, it is suggested that the gradually increased vortex-scale surface enthalpy flux has a leading role in the development of vigorous convection. The results also highlight the potentially dominant role of weak to moderate convection in the onset of RI, while the convective bursts play a supporting role. Based on the aforementioned analyses, a schematic diagram is shown to describe the plausible path leading to RI. [ABSTRACT FROM AUTHOR]

In the frame of the SWOP (sounding water vapour, ozone, and particle) campaign during the Asian summer monsoon (ASM), ozone and water vapour profiles were measured by balloon-borne sensors launched from Lhasa (29.66° N, 91.14° E, elevation 3650 m), China, in August 2013. In total, 24 soundings were launched, nearly half of which show strong variations in the relationship between ozone and water vapour in the tracer-tracer correlation in the upper troposphere and lower stratosphere (UTLS). For each sounding, 20-day backward trajectories were calculated using the trajectory module of the Chemical Lagrangian Model of the Stratosphere (CLaMS) to analyse these variations. The trajectory calculations demonstrate that three tropical cyclones (tropical storm Jebi, typhoons Utor and Trami), which occurred over the western Pacific Ocean during August 2013, had a considerable impact on the vertical distribution of ozone and water vapour by uplifting marine air masses to altitudes of the ASM anticyclone. Air parcels subsequently arrived at the observation site via two primary pathways: firstly via direct horizontal transport from the location of the typhoon to the station within approximately 3 days, and secondly via transport following the clockwise wind flow of the ASM within a timescale of 1 week. Furthermore, the interplay between the spatial position of the ASM anticyclone and tropical cyclones plays a key role in controlling the transport pathways of air parcels from the boundary layer of the western Pacific to Lhasa in horizontal and vertical transport. Moreover, the statistical analysis shows that the strongest impact by typhoons is found at altitudes between 14.5 and 17 km (365-375 K). Low ozone values (50-80 ppbv) were observed between 370 and 380K due to the strong vertical transport within tropical cyclones. [ABSTRACT FROM AUTHOR]

With the changes in the nature and the society, risks will inevitably change. It implies that, with the passage of time, some historical data would be invalid for probabilistic risk analysis. In this paper, a model to acquire the valid data is suggested, which is based on the Mann- Kendall test to detect abrupt change-point on time series data. What's more, the typhoon risk analysis in Guangdong Province, China is used as a case study to show how to apply the model. The valid data of the intensities of typhoons and the related losses in the province for the probabilistic risk analysis is obtained from the data during the time from 1984 to 2012. Comparing with the results based on the set of invalid data and the set of all collected data, the assessed risk based on the valid data is more reliable, which could reflect the dynamics of the typhoon risk. [ABSTRACT FROM AUTHOR]

This study investigates the effects of climatic variations and extremes captured by variability in temperature, precipitation, and incidents of typhoons on aggregate inter-provincial migration within the Philippines using panel data. Our results indicate that a rise in temperature and to some extent increased typhoon activity increase outmigration, while precipitation does not have a consistent, significant effect. We also find that temperature and typhoons have significant negative effects on rice yields, a proxy for agricultural productivity, and generate more outmigration from provinces that are more agriculturally dependent and have a larger share of rural population. Finally, migration decisions of males, younger individuals, and those with higher levels of education are more sensitive to rising temperature and typhoons. We conclude that temperature increase and to some extent typhoon activities promote migration, potentially through their negative effect on crop yields. The migration responses of males, more educated, and younger individuals are more sensitive to these climatic impacts. [ABSTRACT FROM AUTHOR]

Kim, K.O.; Yuk, J.-H.; Jung, K.T., and Choi, B.H., 2017. Swell propagation caused by typhoon passage to the Yellow and East China Seas. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 144-148. Coconut Creek (Florida), ISSN 0749-0208. Typhoons generate big swells frequently propagating over the East China Sea, the wide continental shelf sea with depth shallower than 200 m. The characteristic features of swell propagation into the Yellow and East China Seas caused by typhoon Herb in 1996 has been investigated applying a ray-tracing technique and a spectral wave model (SWAN) with an unstructured-mesh grid system. This study discusses the generation and propagation of the swells into the Yellow and East China Seas using the integration of ray trajectories and model-based simulated wave. Calculated and observed wave heights and periods at Gadeokdo, Korea are found to be in reasonable agreement with each other. [ABSTRACT FROM AUTHOR]

Suh, S.-W.; Kim M.-J., and Kim, H.-J., 2017. Prediction of sand beach variations by coupling of hydrodynamic and morphological models during extreme storms. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 284-288. Coconut Creek (Florida), ISSN 0749-0208. Beaches are constantly affected by hydrodynamic forcing. Among various factors, a wave impact is the major reason for beach formation and erosion. In order to provide efficient coupling for the morphological variations in beaches, we consider an unstructured ADCIRC+SWAN model and an orthogonal curvilinear XBeach model. When coupling these heterogeneous models, external Perl scripts are implemented to automatically convey simulated extreme wave and tide conditions for the XBeach input. The application of the model to the hindcasting of typhoons Maemi and Neoguri at Haeundae Beach in Korea shows satisfactory beach variations. Moreover, through sensitivity tests, we find that a wave height of 2 m behaves as a threshold value in the beach environment. Since the coupled model can be easily extended for real-time simulation, it can be employed in an early-warning system to provide beach safety. [ABSTRACT FROM AUTHOR]

This report presents super-typhoon Yolanda's impacts on coral reefs of Eastern Samar, Philippines, and evaluates its implications on resource management in the area. Coral reefs suffer regular impacts of typhoons, and typhoons nowadays are stronger in magnitude, longer in duration, more frequent in occurrence, and larger in scale. Thus, there is a great need to understand the impacts and consequences of super-typhoons on reefs and the coastal communities. Yolanda is the strongest recorded typhoon to make a landfall. Here is the first account of Yolanda's impacts on corals and benthic organisms, reef fish, and fisheries production. Our study sites covered Lawaan, Balangiga, Giporlos, Quinapondan, Salcedo, and Guiuan in Eastern Samar, Philippines-municipalities that were greatly damaged by Yolanda. To quantify the impacts of Yolanda on coral reefs, we compared coral cover and diversity, and fish abundance, biomass, and diversity between sites before and after Yolanda. We found that some reef areas were completely wiped out by Yolanda (i.e., the shallow branching reefs), but other reef sites were only partially damaged. The extent of damages depends on reef locations relative to Yolanda's trajectory, depth, coral species composition, and reef condition prior to Yolanda. We also found that most reefs in the area already suffered degradation prior to Yolanda (i.e., due to overfishing, destructive fishing, and siltation from land). Active coral restoration, reduction in fishing effort, diversification of economic activities, and effective management of no-take marine reserves should play key roles in the recovery of resources and human lives in these devastated areas. [ABSTRACT FROM AUTHOR]

We use a high-resolution numerical simulation of Atlantic Hurricane Earl (2010) to increase our understanding of Earl's intensification in relatively strong vertical shear in the context of a recent paradigm for tropical cyclone intensification. The integrity of the simulation is judged by comparing analyses thereof with those of the unprecedented observational data gathered in Earl. Consistent with the classical view of spin-up, the amplification of the tangential wind field above the boundary layer is found to occur as the absolute angular momentum surfaces are drawn inwards by the aggregate heating of the rotating convective clouds in the interior of the vortex. In addition to this classical pathway, spin-up occurs within the inner-core boundary layer, where the maximum tangential winds occur. The latter is another element of the new paradigm. Despite the detrimental influence of the shear on the vortex alignment and in depressing the pseudo-equivalent potential temperature outside the developing eyewall, the combined eddy processes associated with the vortical plume structures in and around the developing eyewall region are shown to contribute to an enhanced overturning circulation and an intensifying storm. These eddy processes are distinctly agradient effects that are not features of the classical spin-up mechanism. It remains to be understood how the rotating convective updraughts combine to produce the diagnosed structures of the eddy terms themselves and how vortex Rossby waves and other eddies contribute to the alignment of the vortex during intensification. [ABSTRACT FROM AUTHOR]

Diameter distributions of stand modeling play an important role in forest growth, yield, management, and CO2 fixation. The objective of this study was to describe the parameter predictions of a Weibull model for diameter distribution over 100 years in a pure, even-aged stand of Cryptomeria japonica in Taiwan. Decreasing stand density was influenced by the thinning and typhoon event. The stand height increased with increasing stand age until 45 years, after which stand height remained at 28 ± 0.5 m until 103 years of age, indicating that it had not experienced a typhoon with sustained strong winds causing the trees to lose their tops but survive. The 3D dynamic curve of stand structure was compared with a traditional 2D curve to demonstrate the interrelation between the diameter at breast height (DBH), frequency or tree number, and stand age. The parameters a, b, and c showed that the Weibull distribution moved to the right, the peak intensity of the curve moved toward the right and became weaker and broader with increasing stand age. The DBH curve effectively changed after the thinning treatment with different variation trends for the three Weibull parameters. The Weibull model would facilitate future research to provide a wealth of information on forest management and the estimation of stand wind damage. [ABSTRACT FROM AUTHOR]

The upper-ocean responses to Typhoon Megi (2010) are investigated using data from ARGO floats and the satellite TMI. The experiments are conducted using a three-dimensional Princeton Ocean Model (POM) to assess the storm, which affected the Northwest Pacific Ocean (NWP) and the South China Sea (SCS). Results show that the upwelling and entrainment experiment together account for 93% of the SST anomalies, where typhoon-induced upwelling may cause strong ocean cooling. In addition, the anomalous SST cooling is stronger in the SCS than in the NWP. The most striking feature of the ocean response is the presence of a two-layer inertial wave in the SCS-a feature that is absent in the NWP. The near-inertial oscillations can be generated as typhoon wakes, which have maximum flow velocity in the surface mixed layer and may last for a few days, after the typhoon's passage. Along the typhoon tracks, the horizontal currents in the upper ocean show a series of alternating negative and positive anomalies emanating from the typhoon. [ABSTRACT FROM AUTHOR]

This study explored the impact of coastal radar observability on the forecast of the track and rainfall of Typhoon Morakot (2009) using a WRF-based ensemble Kalman filter (EnKF) data assimilation (DA) system. The results showed that the performance of radar EnKF DA was quite sensitive to the number of radars being assimilated and the DA timing relative to the landfall of the tropical cyclone (TC). It was found that assimilating radial velocity (Vr) data from all the four operational radars during the 6 h immediately before TC landfall was quite important for the track and rainfall forecasts after the TC made landfall. The TC track forecast error could be decreased by about 43% and the 24-h rainfall forecast skill could be almost tripled. Assimilating Vr data from a single radar outperformed the experiment without DA, though with less improvement compared to the multiple-radar DA experiment. Different forecast performances were obtained by assimilating different radars, which was closely related to the first-time wind analysis increment, the location of moisture transport, the quasi-stationary rainband, and the local convergence line. However, only assimilating Vr data when the TC was farther away from making landfall might worsen TC track and rainfall forecasts. Besides, this work also demonstrated that Vr data from multiple radars, instead of a single radar, should be used for verification to obtain a more reliable assessment of the EnKF performance. [ABSTRACT FROM AUTHOR]

The improved Weather Research and Forecasting model was used to simulate Typhoon Megi, which experienced rapid intensification ( RI) and gradual intensification processes. The model reproduced the typhoon track and intensity in accordance with the best-track observations. Our study has shown that in small or moderate shear environments, the great latent heat released in the upper troposphere through the enhancement of convective bursts, which enhanced the upper-level warm core and caused the intensification of typhoon. During the onset of RI, strong convective cells were found gathering in downshear eyewall quadrant or the left side of shear. They also indicated an asymmetric structure in the eyewall. As Megi intensified rapidly, the strong convective activity occurred both in upshear and downshear quadrants, then the symmetrical structures developed well. [ABSTRACT FROM AUTHOR]

ABSTRACT An analysis of tropical cyclone ( TC) data from 1951 to 2013 in the Philippines revealed that an average of 19.4 TCs enter the Philippine Area of Responsibility ( PAR) every year and nine TCs cross the country. Time series analysis of the TC datasets shows no significant trends in the annual number of TCs in PAR but a slightly decreasing trend in the number of landfalling TCs in the Philippines, particularly in the last two decades. However, while the analysis shows fewer typhoons (above 118 kph), more extreme TCs (above 150 kph) have affected the Philippines. The study also confirms that the Northern island of Luzon is most frequently hit by TCs, and that TC-associated rainfall is greatest in this region compared to the southernmost part of the country. The impact of TCs shows a consistently increasing trend in economic losses and damages. Further understanding of past and future trends of TC activity in the Western North Pacific Basin, and the PAR, including the impacts associated with them, will provide valuable insights for climate change adaptation and disaster risk management. [ABSTRACT FROM AUTHOR]

This study examines the formation of a double warm-core (DWC) structure in intense tropical cyclones (TCs) that was captured in almost all supertyphoon cases during the 2012-14 real-time typhoon forecasts in the northwestern Pacific basin with the Hurricane Weather Research and Forecasting Model (HWRF). By using an idealized configuration of HWRF to focus on the intrinsic mechanism of the DWC formation, it is shown that the development of DWC in intense TCs is accompanied by a thin inflow layer above the typical upper outflow layer. The development of this thin inflow layer in the lower stratosphere (~100-75 hPa), which is associated with an inward pressure gradient force induced by cooling at the cloud top, signifies intricate interaction of TCs with the lower stratosphere as TCs become sufficiently intense, which has not been examined previously. Specifically, it is demonstrated that a higher-level inflow can advect potentially warm air from the lower stratosphere toward the inner-core region, thus forming an upper-level warm core that is separated from a midlevel one of tropospheric air. Such formation of the upper-level warm anomaly in intense TCs is linked to an episode of intensification at the later stage of TC development. While these results are produced by HWRF, the persistent DWC and UIL features in all HWRF simulations of intense TCs suggest that the lower stratosphere may have significant impacts on the inner-core structures of intense TCs beyond the current framework of TCs with a single warm core. [ABSTRACT FROM AUTHOR]

On September 9, 2015, typhoon number 18 brought unprecedented rainfall to northern Japan, particularly to Kanto and Tohoku regions. As a result, flood damage and sediment disasters occurred in various locations including an overflow in Kinu River at Wakamiyado and levee failure in Kinu River at Misaka-cho. During the disaster, upstream of Kinu River has received more than 600 mm precipitation in 48 hrs which is more than twice the amount which usually received throughout the entire month of September. This unprecedented rainfall, has caused huge disaster to the people in Ibaraki prefecture particularly Joso city where the entire city has been recoded an inundation of about 1 - 2 m depth and it has been over 3 m in some areas. A small river (Hachikenbori River) flowing through the center of the flood plain was assumed to be the cause for earlier inundations in the downstream. We developed a coupled flood inundation model for the area with 1D and 2D hydrodynamic models, to study the effect of the Hachikenbori River for the inundations. The model includes the overbank flow and the flow due to river bank failure in Kinu River and Hachikenbori River. The developed model was validated with the observed data of inundations and water levels at Hachikenbori River. The results from the analyses performed with and without Hachikenbori River indicate that Hachikenbori River caused the early inundations in some places. Numerical results suggest that the Hachikenbori River has reduced the inundation area by 1 km 2 by allowing the flood water to pass quickly. However, there is no difference in the inundation heights of the cases carried out with and without Hachikenbori River. [ABSTRACT FROM AUTHOR]

Typhoon Mireille (1991) caused devastation over Japan. Assessing the impacts of such an extreme typhoon under global warming is an important task to prevent and mitigate future natural disasters. This study investigated the influences of global warming on the strong winds of Typhoon Mireille by conducting pseudo-global warming (PGW) experiments with a regional model. Since significant damages to forest areas occurred in Kyushu and Tohoku, we compared the typhoon impacts in these two regions. It was demonstrated that on average the mean wind speeds induced by Typhoon Mireille become stronger in Kyushu and weaker in Tohoku under the PGW conditions than under the September 1991 conditions. The difference between the two regions in the future is due to the simulated typhoons under PGW being stronger at lower latitudes and weakening more rapidly at higher latitudes. Thus, the impacts of Typhoon Mireille under a warmed climate are considered to be more severe at a lower latitude and weaker at a higher latitude. [ABSTRACT FROM AUTHOR]

This study investigated the effects of two typhoons (Nari and Wipha) on sea surface temperature (SST) and chlorophyll- a (Chl- a) concentration. Typhoons Nari and Wipha passed through the Yellow Sea on September 13, 2007 and the East China Sea (ECS) on September 16, 2007, respectively. The SST and Chl- a data were obtained from the Aqua/Terra MODIS and NOAA18, respectively, and the temperature and salinity in the southeast of the study area were observed in situ from Argo. The average SST within the study area dropped from 26.33°C on September 10 to a minimum of 22.79°C on September 16. Without the usual phenomenon of 'right bias', the most striking response of SST was in the middle of the typhoons' tracks, near to coastal waters. Strong cooling of the upper layers of the water column was probably due to increased vertical mixing, discharge from the Changjiang River estuary, and heavy rainfall. During the typhoons, average Chl- a increased by 11.54% within the study area and by 21.69% in the offshore area near to the southeast ECS. From September 1 to 13, average Chl- a was only 0.10 mg/m in the offshore waters but it reached a peak of >0.17 mg/m on September 18. This large increase in Chl- a concentration in offshore waters might have been triggered by strong vertical mixing, upwelling induced by strong typhoons, and sedimentation and nutrient influx following heavy rainfall. [ABSTRACT FROM AUTHOR]

The results are presented ofcomputation oftrajectory and intensity oftwo typhoons in 2012 for two groups of parameterization schemes of ocean-atmosphere energy exchange in tropical cyclones (TCs), boundary and surface layers of TCs, radiation fluxes, microphysics, and convection. The surface layer computations were carried out with and without the relationships that take into account the surface layer cool ing due to spray evaporation. It is demonstrated that the accounting of this effect exerts positive influence on the results of TC trajectory modeling at different stages. Ifthere are specific features in TC movement, for example, the loop formation, this improvement may be crucial. The accuracy ofthe results of computation of TC intensity increases as well. [ABSTRACT FROM AUTHOR]

This study documents observational changes in the eyewall of Typhoon Fanapi (2010) after landfall in Taiwan. The observations indicate that Fanapi's eye and eyewall disappeared on the eastern side of Taiwan's Central Mountain Range (CMR) after landfall, but reemerged on the western side of CMR. The cyclonic circulation, increasing wind speed, a low-level low pressure and high temperature zone, the associated updrafts and downdrafts, and surface pressure and rainfall measurements all support the existence of a reintensified eyewall. The storm slowed down during the redeveloping stage, thus prolonging the rainfall duration over Taiwan. On the western side of CMR a northwest-southeast-oriented rainband formed at an earlier stage, possibly due to the large-scale interaction between Fanapi's remnant flow and the environment. However, the subsequent reintensification might be attributed to the interaction between the circulation and topography. This is supported by the finding that adjacent to CMR, strong wind develops vertically from lower levels, indicating that the reintensification appears to be initiated through a bottom-up process. A vorticity budget analysis shows that at lower layers the stretching mechanism plays a leading role in increasing positive vorticity, followed by the contributions from tilting and horizontal advection. The horizontal advection plays a comparable role to the vertical advection in increasing low- to midlevel vorticity. The vertical advection aloft is responsible for transporting the vorticity upward. Finally, this research provides a relatively rare documentation of the vortical hot towers (VHTs) over terrain using ground-based radars, in contrast to most previous studies focusing on maritime VHTs using simulations or aircraft measurements. [ABSTRACT FROM AUTHOR]

In order to investigate the environment and acoustic filed change induced by typhoon in shallow sea, we conducted two experiments just before and after the passage of typhoon Damrey, which is the strongest to affect the area north of the Yangtze River since 1949, in the Yellow sea in 2012. The data show that the temperature of the whole water column increases dramatically except the sea surface layer after the passage of Damrey while the salinity decreases obviously. The thermocline deepens and weakens, which leads to a change of internal wave activity. The transmission losses (TL) of the two experiments show that the environment change induced by typhoon can increase the TL as large as 8 dB at a distance of 9.2 km and depth of 15 m. The scintillation index (SI) of the sound intensity is simulated to estimate the change of the effect of internal wave activity on acoustic field showing that the SI decreases to a half after the typhoon's passage. The normal mode structures of the two experiments are also significantly different due to the thermocline changes. In addition, the signal arrives earlier after the typhoon's passage due to the water temperature increase. [ABSTRACT FROM AUTHOR]

Understanding factors controlling ecosystem structure and function is key to predicting the effects of climate change on vegetation distribution and carbon sequestration. Cyclones play a large role in structuring ecosystems and cyclone intensity is expected to increase on a warming planet. The effects of cyclones on broad-scale ecosystem patterns could be substantial but are poorly understood. This study assessed forest structure and biodiversity patterns across an elevation gradient (300-3000 m) in mountainous, humid forests of Taiwan, an island experiencing an average of 3-6 typhoons (regional name of cyclones) annually, and contrasted those patterns with a gradient within the Wuyi Mountains of China (500-2100 m), where the climate is similar to Taiwan but typhoon occurrence is rare and effects are generally minimal. In both Taiwan and the Wuyi Mountains, tree species richness and diversity decreased with increasing elevation. Tree size and stature decrease from low to high elevations in the typhoon-protected Wuyi Mountains. In contrast, the biomass and stature of forests in Taiwan increased from low to high elevations. The relationship between forest stature and climate was also contrasting in relation to typhoon disturbance in that we found decreasing tree height and basal area with increasing temperature in Taiwan, but not in the Wuyi Mountains. The more than twofold increase in tree height and biomass with increasing elevations reported here for subtropical humid forests of Taiwan is a unique pattern that highlights the potential role of cyclones in driving elevational patterns of forest structure. Climate change-induced alterations in tropical cyclone regimes may affect elevational patterns of forest structure and carbon sequestration in regions experiencing frequent cyclones. [ABSTRACT FROM AUTHOR]

The interdecadal changes in typhoon (categories 1-3) frequency and its genesis condition over the western North Pacific during the period of 1979-2011 are investigated with consideration for discrepancies among best track datasets. To tide over data uncertainty, a detection-produced dataset is utilized as a homogeneous dataset with five available best track datasets. Typhoon experienced interdecadal changes around the mid-1990s and the mid-2000s in their genesis conditions. Even under the oceanic warm state, typhoon frequency has decreased since the mid-1990s, showing a northwestward movement of its genesis location over the main formation region. The eastward gradient of vertical wind shear is the most significant factor for the change in typhoon genesis condition in recent decades. The vertical wind shear behavior is strongly linked with zonal asymmetry of local SST. We demonstrate that a westward gradient of local SST is the most important modulator of the recent typhoon behavior through the movement of favorable genesis location. The present results indicate that the horizontal distribution, not magnitude, of local SST can be a key factor for prediction of future typhoon activity, thus contributing to natural disaster mitigation and climate change adaptation strategies. [ABSTRACT FROM AUTHOR]