Severe Tropical Storms Research Articles

Field Observations of Changes in SST, Chlorophyll and POC Flux in the Southern East China Sea Before and After the Passage of Typhoon Jangmi

Severe tropical storms play an important role in triggering phytoplankton blooms, yet direct field observation of evidence of the effects of a typhoon is very rare. Sea surface temperature (SST), nitrate concentration, chlorophyll a (chl a) concentration, and particulate organic carbon (POC) flux were measured before and shortly after Typhoon Jangmi which affected the southern East China Sea (SECS) on September 28 ~ 29, 2008. In situ SST (27.5 ~ 28.0°C) on September 19 ~ 21, decreased to ~24.0°C (October 3 ~ 6) in the SECS 4 ~ 7 days after the passage of Typhoon Jangmi. In situ nitrate and chl a concentrations 7-days (on October 6) after the passage of Jangmi were 1.9 μM and 1.61 mg m^(-3), respectively, much higher than those (nitrate: 0.3 μM and chl a: 0.73 mg m^(-3)) concentrations before the typhoon (September 21). The enhanced chl a concentration is thus caused by a nutrient supply via vertical mixing or upwelling in the euphotic zone. The POC flux 7-days after Jangmi's passage was 552 ± 28 mg-C m^(-2) d^(-1), a ~2.5-fold increases before the typhoon (224 ± 33 mg-C m^(-2) d^(-1), on September 21). Our results suggest that typhoons indeed can stimulate efficient POC export out of the euphotic zone, while it is still poorly understood with regard to the total effects of a typhoon on nutrient dynamics and detailed carbon sequestration due to sampling difficulty. Therefore, successional sea-going observations ought to be conducted in the affected area after the passage of typhoons.

Effects of Vertical Wind Shear, Radiation, and Ice Clouds on Precipitation Distributions During a Landfall of Severe Tropical Storm, Bilis (2006)

Torrential rainfall responses to vertical wind shear, radiation, and ice clouds during the landfall of severe Tropical Storm, Bilis (2006) are investigated via a rainfall partitioning analysis of grid-scale sensitivity experiment data. The rainfall data are partitioned into eight types based on surface rainfall budget. The largest contributions to total rainfall come from local atmospheric moistening, water vapor convergence, and hydrometeor loss/convergence (Type 3; 29%) when the large-scale upward motions occurred only in the upper troposphere on 15 July 2006. When the large-scale upward motion center moved to the mid troposphere on 16 July, Type 3 hydrometeor loss/convergence (26%) plus local atmospheric drying, water vapor divergence, and hydrometeor loss/convergence (Type 5; 25%) show equally important contributions to total rainfall. The exclusion of vertical wind shear primarily reduced Type 5 rainfall because of the weakened hydrometeor loss/ convergence on 16 July. The removal of cloud radiative effects enhances Type 5 rainfall due to increased local atmospheric drying and hydrometeor loss/convergence on 15 July. The elimination of ice clouds generally reduced Type 2 rainfall through the decreases in local atmospheric drying, water vapor convergence, and hydrometeor gain/divergence and Type 3 rainfall over two days.

Statistical features of tropical cyclones affecting China and its key economic zones

Recent trends and variability in tropical cyclone (TC) frequency and intensity are examined for TCs that affected China, with particular focus on those TCs that affected China’s key economic zones (e.g., the Yangtze River Delta, the Pearl River Delta, and the Beijing-Tianjin area). The results show that the frequency of TCs affecting China weakly declined during the 1980s and 2000s, followed by a slight increase. The time series of TC frequency shows insignificant variations at periods of 2–6 yr during the past 60 years; these variations are significantly correlated with ENSO activity. The frequency of TCs affecting the Pearl River Delta area is strongly correlated with the ENSO cycle while the frequency of TCs affecting the Yangtze River Delta is not. The TC frequency varies differently for TCs of different intensities. Tropical storms (TSs) affecting China were small in total number, but have clearly increased in frequency. The frequencies of severe tropical storm (STS), typhoon (TY), severe typhoon (STY), and super typhoon (super TY) affecting China declined significantly during the 1970s and 1980s, but the numbers of STY and super TY have increased over the 2000s. The typical intensity of TCs affecting China declined over the 60-yr timeframe, but increased over the most recent 10 years (2000–2010). This increase in the intensity of TCs has particularly impacted the Yangtze River Delta area, which has experienced increased numbers of STYs and super TYs. These tendencies are observed in changes of the maximum intensity of TCs affecting both China in general and the Yangtze River Delta in particular during both the full 60-yr analysis period and the latest 10-yr period; however, these tendencies are not observed in changes of the average intensity of TCs. By contrast, both the extreme intensity and the average intensity of TCs affecting the Pearl River Delta have decreased throughout the analysis period, including the most recent decade.

Lightning Distribution and Eyewall Outbreaks in Tropical Cyclones during Landfall

Abstract Cloud-to-ground lightning data and storm intensity data (winds and central pressure) for 33 northwest Pacific tropical cyclones were used to analyze lightning distributions during the period of landfall in China. Lightning activities varied enormously from storm to storm with an average flash rate over 500 km of radius from 3 to 3201 flashes per hour, and no obvious relationship between average intensity and average flash rate occurred. The maximum flash density shifted from the eyewall region (0–60 km) to outer rainbands (180–500 km) as the intensity level increased. The average ratio of flash density in the eyewall to outer rainband was highest (1:0.5) for storms with the level of a tropical storm (17.2–24.4 m s−1) and lowest (1:8.6) for severe typhoons (41.5–50.9 m s−1). After storm landfall, flash density in the rainband decreased more rapidly in severe typhoons than in severe tropical storms (24.5–32.6 m s−1) and typhoons, but increased in tropical depressions (10.8–17.1 m s−1) and tropical storms. With the strength of intensity level, lightning in the outer rainband gradually weakened after the storm landfall. Lightning outbreaks were identified in a consistent manner for all tropical cyclones to inspect the relationship of eyewall flashes to the changes of structure and intensity. Eyewall flash outbreaks were found during the period of intensity change (15% of outbreaks in intensification and 43% in weaken), and the period of maximum intensity (15% of outbreaks) of storms. A new result of this analysis found that 10% of the outbreaks occurred prior to and during periods of storm turning, which is potentially important for the trajectory change forecasting of tropical cyclones.

Cyclonic track analysis using GIS over the Bay of Bengal

This paper examines the frequency, historical records, and severe cyclonic track of cyclones over the Bay of Bengal for the last 100 years. Bangladesh is located in the path of tropical cyclones originating from the Bay of Bengal. The unique combination of a large astronomical tide, a funneling coastal configuration, low flat terrain and frequent severe tropical storms occasionally produce storm surges that have killed thousands of people. This paper is an attempt to understand the behavior of this weather phenomenon; condition of formation of tropical cyclone, formation area in the Bay of Bengal, seasons of formation, landfall area, track preparation, etc. GIS method has been used to find out the formation area and tracks of Tropical Cyclones over the Bay of Bengal. The frequency of formation of depression and deep depression, Cyclonic Storms and Severe Cyclonic Storms during a particular month and year during the period of 1908- 2008 shows that most of these are formed in the Bay of Bengal during June to November with the highest frequency in August followed by September. It is predicted that the study will help understanding the magnitude of the problems to the concern authorities to reduce cyclonic damages in Bangladesh.

A numerical study of the interaction between two simultaneous storms: Goni and Morakot in September 2009

Significant anomalous tracks were observed when the severe tropical storm Goni (0907) and typhoon Morakot (0908) in September 2009 were evaluated in short distances. The relationship between the two is regarded as a case of binary interaction. Based on an MM5 model (fifth-generation mesoscale model of Pennsylvania State University-National Center for Atmospheric Research), in this study a series of sensitivity experiments were designed to determine the binary interaction between them. The sensitivity of the storm characteristics to the binary interaction was demonstrated through modeling experiments with different TC intensities and sizes based on the bogus vortices initialization. Furthermore, the contributions of large-scale environmental flow and the effects of interaction between the motions of the cyclones were distinguished by numerical experiments using only one of the TC vortices. Results from these experiments show that Morakot (0908) had a greater impact on the motion of Goni (0907), whereas Goni (0907) had a relatively limited impact on Morakot (0908). At the upper level, the northeasterly jet flow in the third quadrant of Morakot (0908) enhanced the upper-level divergence of Goni (0907) and had an important role in maintaining and increasing Goni’s (0907) intensity. And at the lower level, Morakot (0908), with strong convergence and ascending airflow, made a stable transport channel of southwesterly warm and wet flow, thus supporting the lower-level water vapor convergence of Goni (0907). Goni (0907), which was located upriver of the southwesterly flow, intercepted part of the water vapor transportation in the southwesterly flow, causing the water vapor convergence to strengthen while the water vapor convergence of Morakot (0908) weakened.

Appraisal of the prevalence of severe tropical storms over Indian Ocean by screening the features of tropical depressions

Tropical cyclones are one of the nature’s most violent manifestations and potentially the deadliest of all meteorological phenomena. It is a unique combination of violent wind, heavy rainfall, and mountainous waves in sea. The maximum sustained wind speed, minimum sea level pressure, and the radius of maximum winds are important parameters for understanding a particular tropical cyclone and to differentiate it from a depression to tropical storms. The objective of this particular paper is to identify a possible range of maximum sustained wind speed, minimum sea level pressure, and radius of maximum winds which facilitates tropical depressions to lead to tropical storms over Bay of Bengal and Arabian Sea of Indian Ocean basin. The method of rough set theory which is based on condition—decision support system is implemented for the purpose. The result reveals that the threshold ranges of the maximum sustained wind speed, minimum sea level pressure and radius of maximum winds associated with tropical depression are possible that can aid in the predictability of tropical storm over Indian Ocean. The results are validated with significant tropical storms of 2009 and 2010 observations through Doppler and satellite imageries.

Wind data collected by a fixed-wing aircraft in the vicinity of a tropical cyclone over the south China coastal waters

The fixed-wing aircraft of Government Flying Service of the Hong Kong Government has recently equipped with an upgraded meteorological measuring system. This system provides horizontal wind velocity components up to 90 m/s at an accuracy of 0.5 m/s for straight and level flight. Besides search and rescue (SAR) missions, this aircraft is also used for windshear and turbulence investigation flights at the Hong Kong International Airport. In a SAR operation in July 2009, the aircraft flew close to the eye of tropical cyclone Molave, when it was located at about 200 km to the east of Hong Kong over the south China coastal waters. The aircraft provided valuable information about the winds in association with Molave because aircraft reconnaissance for tropical cyclones is not carried out for South China Sea. Based on the aircraft measurements, the 1-second mean wind reached the maximum value of 88 knots at a height of 200 m above mean sea level. Assuming a power law with altitude with an exponent of 0.11 over open waters, the corresponding 1-second mean wind at a height of 10 m would be about 63 knots. The maximum 10-minute mean wind reached 69 knots with an average height of 260 m above mean sea level. The corresponding mean at 10 m would be about 48 knots. As such, based on the aircraft measurements (in which the aircraft might not fly into the areas of maximum winds associated with the tropical cyclone), Molave had at least a strength of tropical storm to severe tropical storm at the times of the measurements. Nowadays, the determination of the intensity of tropical cyclones over the South China Sea is normally based on remote sensing data only (e.g. radar and satellite observations). To the knowledge of the authors, the results presented in the paper are the first time that direct measurements of the winds near the centre of a tropical cyclone over the northern part of the South China Sea are made with an aircraft. Apart from the mean wind and gust, other properties of the wind field of Molave are studied, e.g. frequency spectrum of the horizontal wind data, and thus the turbulence associated with this tropical cyclone.

Tropical cyclones in China: County-based analysis of landfalls and economic losses in Fujian Province

Most of China’s coastline is economically developing, densely populated, and frequently hit by landfalling Tropical Cyclones (TCs). Economic losses below province level have not been systematically analyzed due to lack of data. The objective of this paper is to conduct a TC loss assessment on county level in Fujian Province, coastal SE China, and to break down economic losses from province-scale to smaller administrative units. A unique loss database established by the China Meteorological Administration (CMA) and National Climate Center is used, and four entries at county-level are derived: location of losses due to TC, total economic losses per TC, start time of TC, and end time of TC. Tracks and intensities of TCs from 1949–2008 are derived from the CMA and Shanghai Typhoon Center annual typhoon yearbooks. Physical and economic data are overlaid in a Geographical information System. The landfall spots of TCs on China’s mainland coastline from 1949–2008 are determined by generating segments of 1° length. The result shows that Guangdong Province (South China) and Fujian Province (South-East China) host distinct hot spots where TCs make frequent landfall. All TCs making landfall in Central-North Fujian originated from the West North Pacific and none from the South China Sea. Direct economic losses in 25 counties along Fujian’s coastline due to TCs from 1984–2007 are analyzed and corrected with the Consumer Price Index. Some counties report losses frequently at low magnitude but seldom at high magnitude. Others like urban Fuzhou experience losses above 10 million CNY per TC, the most costly one 70 times higher. Other rural counties might experience economic losses far below 10 million CNY when being hit. Landfalling TCs in average cause economic losses of minimum 10 million CNY in 21 of 25 counties. In roughly one third of the counties, economic losses account for more than 30 million CNY when a TC has impact. The average economic losses per TC are 0.2–0.5% of the counties’ GDP (South and North of Fujian’s coastline) and even more than 0.5% of the GDP in North-East Fujian. The economic impacts of TCs are higher along the southern and northern coastline of Fujian Province where TC landfall activity is higher, but higher economic losses are triggered by higher GDP in these counties. The most costly TCs in Fujian had intensities of Severe Tropical Storm or Typhoon and occurred mostly in the 2000’s after making landfall in July.

Comparative Effects of Different Disturbances in Coral Reef Habitats in Moorea, French Polynesia

Degradation and loss of critical coastal habitats has significant ramifications for marine fisheries, such that knowledge of changes in habitat quality and quantity are fundamental to effective ecosystem management. This study explores changes in the structure of coral reef habitats, specifically changes in coral cover and composition, in Moorea, French Polynesia, to assess the independent and combined effects of different disturbances since 1979. During this period, reefs on the north coast have been subject to coral bleaching, severe tropical storms, as well as outbreaks ofAcanthaster. Coral cover varied significantly among years, showing marked declines during some, but not all, disturbances. The greatest rates of coral loss coincided with outbreaks ofA. planci. Moreover, successive disturbances have had differential effects among coral genera, leading to strong directional shifts in coral composition.Acroporais declining in abundance and coral assemblages are becoming increasingly dominated byPocillopora and Porites. Observed changes in the cover and composition of corals are likely to have further significant impacts on the reef fish assemblages. Given that significant disturbances have been mostly associated with outbreaks ofA. planci, rather than climate change, effective ecosystem management may reduce and/or delay impending effects of climate change.

Torrential rainfall responses to radiative and microphysical processes of ice clouds during a landfall of severe tropical storm Bilis (2006)

Ice clouds are an important component in precipitation systems. The radiative processes of ice clouds directly impact radiation in heat budget and the microphysical processes of ice clouds directly affect latent heat and net condensation through deposition processes, which may eventually change surface rainfall. Thus, torrential rainfall responses to radiative and microphysical processes of ice clouds during a landfall of severe tropical storm Bilis (2006) are investigated with the analysis of sensitivity experiments. The two-dimensional cloud-resolving model is integrated for 3 days with imposed zonally uniform vertical velocity, zonal wind, horizontal temperature and vapor advection from NCEP/GDAS data. One sensitivity experiment excludes the radiative effects of ice clouds and the other sensitivity experiment excludes ice microphysics and associated radiative and microphysical processes. Model domain mean surface rain rate is barely changed by the exclusion of radiative effects of ice clouds due to the small decrease in net condensation associated with the small reduction in latent heat as a result of the offset between the increase in radiative cooling and the decrease in heat divergence. The exclusion of microphysical effects of ice clouds decreases the mean rain rate simply through the suppression of latent heat as a result of the removal of deposition processes. The total exclusion of ice microphysics decreases the mean rain rate mainly through the exclusion of microphysical effects of ice clouds.

The effect of typhoon on particulate organic carbon flux in the southern East China Sea

Abstract. Severe tropical storms play an important role in triggering phytoplankton blooms, but the extent to which such storms influence biogenic carbon flux from the euphotic zone is unclear. In 2008, typhoon Fengwong provided a unique opportunity to study the in situ biological responses including phytoplankton blooms and particulate organic carbon fluxes associated with a severe storm in the southern East China Sea (SECS). After passage of the typhoon, the sea surface temperature (SST) in the SECS was markedly cooler (∼25 to 26 °C) than before typhoon passage (∼28 to 29 °C). The POC flux 5 days after passage of the typhoon was 265 ± 14 mg C m−2 d−1, which was ∼1.7-fold that (140–180 mg C m−2 d−1) recorded during a period (June–August, 2007) when no typhoons occurred. A somewhat smaller but nevertheless significant increase in POC flux (224–225 mg C m−2 d−1) was detected following typhoon Sinlaku which occurred approximately 1 month after typhoon Fengwong, indicating that typhoon events can increase biogenic carbon flux efficiency in the SECS. Remarkably, phytoplankton uptake accounted for only about 5% of the nitrate injected into the euphotic zone by typhoon Fengwong. It is likely that phytoplankton population growth was constrained by a combination of light limitation and grazing pressure. Modeled estimates of new/export production were remarkably consistent with the average of new and export production following typhoon Fengwong. The same model suggested that during non-typhoon conditions approximately half of the export of organic carbon occurs via convective mixing of dissolved organic carbon, a conclusion consistent with earlier work at comparable latitudes in the open ocean.

Cloud radiative effects on responses of rainfall to large-scale forcing during a landfall of severe tropical storm Bilis (2006)

The cloud radiative effects on responses of rainfall to the large-scale forcing during a landfall of severe tropical storm Bilis (2006) are investigated by analyzing sensitivity experiments imposed by large-scale forcing from NCEP/GDAS data in a two-dimensional cloud-resolving model. The daily average analysis is conducted on 15 and 16 July 2009, respectively, due to dominant stratiform and convective rainfall associated with different large-scale forcing. When cloud radiative effects are excluded, the increased mean rainfall is associated with the increased mean radiative cooling through the enhanced mean latent heat on 15 July. The reduction in mean rain rate is related to the slowdown in the mean net condensation while the enhanced mean radiative cooling from the removal of cloud radiative effects is balanced by the suppressed heat divergence on 16 July. The increased mean rainfall on 15 July and decreased mean rainfall on 16 July are mainly from raining stratiform regions. The enhanced stratiform rainfall is associated with the weakened local atmospheric moistening and strengthened local hydrometeor loss on 15 July, whereas the reduced stratiform rainfall is related to the weakened water vapor convergence on 16 July.When cloud-radiation interaction is excluded, the decreases in the mean rain rate are associated with the slowdown in the mean hydrometeor loss on 15 July and the suppression in the net condensation on 16 July. The decreased mean rainfall is mainly from convective regions on 15 July and raining stratiform regions on 16 July. The reduced convective rainfall is associated with strengthened transport of hydrometeor concentration from convective regions to raining stratiform regions on 15 July, whereas the decreased stratiform rainfall is related to the weakened water vapor convergence on 16 July.

Improving Wind and Rain Simulations for Tropical Cyclones with the Assimilation of Doppler Radar Data

More accurate prediction of the strong winds and heavy rain associated with tropical cyclones using numerical weather prediction (NWP) models would be helpful in the provision of weather services for the public. In this paper, the impact of assimilating radar data in the simulation of Typhoon Neoguri and Severe Tropical Storm Kammuri in 2008 is studied using Weather Research and Forecasting (WRF) version 2.2 and WRF VAR version 2.1. Only the data from the radar at Tate's Cairn in Hong Kong are considered. Four experiments are conducted, namely, (a) simulation without radar data, (b) simulation with radar data assimilated at the initial time, (c) cycling simulation with the assimilation of radar data (Doppler velocity and reflectivity) directly assimilated, and (d) cycling simulation with the assimilation of 2D wind field retrieved from the Doppler velocity data from the radar. By comparing with actual observations of the surface wind distribution in Hong Kong and the actual radar reflectivity data, it turns out that both (c) and (d) outperform (a) and (b), and (c) and (d) show comparable skills. As a result, cycling simulation with the assimilation of weather radar data (even for a single radar) could improve the prediction of winds and rain bands associated with tropical cyclones.

Intense Rainfalls on August 17, 1968 over the Kiso-Hida and Nagara River Basin in Japan Associated with Intrusion of Middle Tropospheric Dry Airs over the Low-level Moist Belt

The synoptic-scale condition related to the intense rainfalls on August 17, 1968, over the Kiso?Hida and Nagara River Basin in the central part of Japan is studied by using European Center for Medium-Range Weather Forecasts 40-year reanalysis data and upper, synoptic-surface, local rain-gauge observation data and satellite cloud images.The intense rainfalls occurred within a long cloud belt formed with a low-level moist belt (LMB), which had formed along the northwestern rim of the North Pacific subtropical anticyclone (NPSA). The LMB was sustained by large-scale moisture transport along the northern rim of the NPSA and mesoscale northward moisture transport along a small anticyclone embedded in the NPSA. In the lower and middle troposphere, dry air spread over the Japan Sea after the passage of a severe tropical storm (STS) over the Japan Sea owing to the prevailing westerlies to the southwest of the STS. The northern edge of the LMB was bounded by the dry air. The northern boundary of the LMB was signified as the dry front because of the strong moisture gradient and very weak thermal gradient.Intense rainfalls occurred in the cloud belt, at a distance of ∼1200 km south of the STS, over the river basin where the large-scale and the mesoscale moist flows converged in association with the orographic convergence. Intense convective rainfalls were accompanied by the increase in the convective instability due to the southeastward intrusion of the middle tropospheric dry air over the LMB. Significant low-level jet stream and mesoscale depression were not found around the intense rainfall area.

Responses of vertical structures in convective and stratiform regions to large-scale forcing during the landfall of severe tropical storm Bilis (2006)

The responses of vertical structures, in convective and stratiform regions, to the large-scale forcing during the landfall of tropical storm Bilis (2006) are investigated using the data from a two-dimensional cloud-resolving model simulation. An imposed large-scale forcing with upward motion in the mid and upper troposphere and downward motion in the lower troposphere on 15 July suppresses convective clouds, which leads to ∼100% coverage of raining stratiform clouds over the entire model domain. The imposed forcing extends upward motion to the lower troposphere during 16–17 July, which leads to an enhancement of convective clouds and suppression of raining stratiform clouds. The switch of large-scale lower-tropospheric vertical velocity from weak downward motion on 15 July to moderate upward motion during 16–17 July produces a much broader distribution of the vertical velocity, water vapor and hydrometeor fluxes, perturbation specific humidity, and total hydrometeor mixing ratio during 16–17 July than those on 15 July in the analysis of contoured frequency-altitude diagrams. Further analysis of the water vapor budget reveals that local atmospheric moistening is mainly caused by the enhancement of evaporation of rain associated with downward motion on 15 July, whereas local atmospheric drying is mainly determined by the advective drying associated with downward motion over raining stratiform regions and by the net condensation associated with upward motion over convective regions during 16–17 July.

Effects of vertical wind shear on convective development during a landfall of severe tropical storm Bilis (2006)

Effects of vertical wind shear on convective development during the landfall of tropical storm Bilis (2006) are investigated with a pair of sensitivity experiments using a two-dimensional cloud-resolving model. The validated simulation data from Wang et al. [Wang, D., Li, X., Tao, W.-K., Liu, Y., Zhou, H., 2009: Torrential rainfall processes associated with a landfall of severe tropical storm Bilis (2006): A two-dimensional cloud-resolving modeling study. Atmos. Res., 91, 94–104.] are used as the control experiment. The difference between the control and sensitivity experiments is that vertically varying zonal winds in the control experiment are replaced by their mass-weighted means in the sensitivity experiment. The imposed vertical velocity with ascending motion in the upper troposphere and descending motion in the lower troposphere is responsible for dominant stratiform rainfall on 15 July. The vertical wind shear does not have important impacts on development of stratiform rainfall. One day later, imposed upward motion extends to the lower troposphere. The inclusion of negative vertical wind shear produces well-organized convection and strong convective rainfall because it causes kinetic energy transfer from large-scale forcing to perturbation circulations.

Observational Analysis of Heavy Rainfall Mechanisms Associated with Severe Tropical Storm Bilis (2006) after Its Landfall

Abstract This observational study attempts to determine factors responsible for the distribution of precipitation over large areas of southern China induced by Bilis, a western North Pacific Ocean severe tropical storm that made landfall on the southeastern coast of mainland China on 14 July 2006 with a remnant circulation that persisted over land until after 17 July 2006. The heavy rainfalls associated with Bilis during and after its landfall can be divided into three stages. The first stage of the rainfall, which occurred in Fujian and Zhejiang Provinces, could be directly induced by the inner-core storm circulation during its landfall. The third stage of rainfall, which occurred along the coastal areas of Guangdong and Fujian Provinces, likely resulted from the interaction between Bilis and the South China Sea monsoon enhanced by topographical lifting along the coast. The second stage of the rainfall, which appeared inland around the border regions between Jiangxi, Hunan, and Guangdong Provinces, caused the most catastrophic flooding and is the primary focus of the current study. It is found that during the second stage of the rainfall all three ingredients of deep moist convection (moisture, instability, and lifting) are in place. Several mechanisms, including vertical wind shear, warm-air advection, frontogenesis, and topography, may have contributed simultaneously to the lifting necessary for the generation of the heavy rainfall at this stage.

A Simulation Tool for Hurricane Evacuation Planning

Atlantic hurricanes and severe tropical storms are a serious threat for the communities in the Gulf of Mexico region. Such storms are violent and destructive. In response to these dangers, coastal evacuation may be ordered. This paper describes the development of a simulation model to analyze the movement of vehicles through I-65, a major US Interstate highway that runs north off the coastal City of Mobile, Alabama, towards the State of Tennessee, during a massive evacuation originated by a disastrous event such a hurricane. The constructed simulation platform consists of a primary and two secondary models. The primary model is based on the entry of vehicles from the 20 on-ramps to I-65. The two secondary models assist the primary model with related traffic events such as car breakdowns and accidents, traffic control measures, interarrival signaling, and unforeseen emergency incidents, among others. Statistical testing was performed on the data generated by the simulation model to indentify variation in relevant traffic variables affecting the timely flow of vehicles travelling north. The performed statistical analysis focused on the closing of alternative on-ramps throughout the Interstate.

Negative entropy flow and the life-cycle of a severe tropical storm

The relationship of the evolution of a severe tropical storm with entropy flow is investigated in this paper, based on the observational analyses covering its whole life-cycle. The formula for calculating entropy flow is derived starting with the Gibbs relation in terms of constant pressure coordinates. The results show that the entropy flow properties of the severe tropical storm are different in the different stages of its life-cycle and negative entropy flow plays an important role in the growth of a storm, suggesting that entropy flow analysis is a powerful tool in understanding the mechanism responsible for the evolution of a storm.