Potential morphological responses of an artificial beach to a flood in extreme events: field observation and numerical modelling

Conch Island is a typical artificial island at the Tanghe Estuary in Bohai Sea,China.To improve natural environment and boost local tourism,beach nourishment will be applied to its north-western shore.The projected beach is landward and opposite to the Jinmeng Bay Beach.Nowadays,with climate changes,frequent heavy rainfalls in Hebei Province rise flood hazards at the Tanghe Estuary.Under this circumstance,potential influences on the projected beach of a flood are investigated for sustainable managements.A multi-coupled model is established and based on the data from field observations,where wave model,flow model and multifraction sediment transport model are included.In addition,the impacts on the projected beach of different components in extreme events are discussed,including the spring tides,storm winds,storm waves,and sediment inputs.The numerical results indicate the following result.(1)Artificial islands protect the coasts from erosion by obstructing landward waves,but rise the deposition risks along the target shore.(2)Flood brings massive sediment inputs and leads to scours at the estuary,but the currents with high sediment concentration contribute to the accretions along the target shore.(3)The projected beach mitigates flood actions and reduces the maximum mean sediment concentration along the target shore by 20%.(4)The storm winds restrict the flood and decrease the maximum mean sediment concentration by 21%.With the combined actions of storm winds and waves,the maximum value further declines by 38%.(5)A quadratic polynomial relationship between the deposition depths and the maximum sediment inputs with flood is established for estimations on the potential morphological changes after the flood process in extreme events.For the uncertainty of estuarine floods,continuous monitoring on local hydrodynamic variations and sediment characteristics at Tanghe Estuary is necessary.

Compound extreme events in Yarlung Zangbo River Basin from 1977 to 2018

Extreme climate events threaten human health,economic development,and ecosystems.Many studies have been conducted on extreme precipitation and temperature changes in the Yarlung Zangbo River Basin(YZRB).However,little attention has been paid to compound climate extremes.In this study,the variations of wet/warm compound extreme events in summer and dry/cold compound extreme events in winter over the past 42 years in the YZRB were investigated using eight extreme climate indices that were estimated using monthly temperature and precipitation observations.The results showed that the numbers of frost days and ice days tended to decrease on the spatiotemporal scale,while the maximum values of daily maximum temperature and daily minimum temperature exhibited increasing trends.The frequency of wet/warm compound extreme events was significantly higher from 1998 to 2018 than from 1977 to 1997.Dry/cold compound extreme events became less frequent from 1998 to 2018 than from 1977 to 1997.The rate of increase of wet/warm compound extreme events was about ten times the absolute rate of decrease of dry/cold compound extreme events.With regard to the spatial pattern,the frequency of wet/warm compound extreme events increased significantly in almost all parts of the YZRB,while that of dry/cold compound extreme events decreased across the basin.This study helps to improve our understanding of the changes in compound precipitation and temperature extremes in the YZRB from a multivariable perspective.

Water Resources and Water Services Infrastructure and Its Vulnerability to Extreme Events—The Case of Jordan

This study discussed the water sector as a critical infrastructural element in Jordan where the sector is exposed to the extreme events. The exposure of the country to extreme events has initiated this study. Such events are Pollution accidents, flooding, draughts, overexploitation, failure in electricity supply, climate changes, earthquakes, landslides, failure of dams, failure of wastewater treatment plants, failure of desalination plants, sabotage, fire, water theft, migration and demographic changes (immigration and urban migration), relations to neighboring countries, epidemics, and others. These extreme events are discussed in this article and the results show that failures in the water infrastructure and water supply, in Jordan, with its water sector situation have rigorous percussions on the country’s health, food supply, economy, societal stability, the built environment, and on other water-related issues. The study concludes that developing national programs to protect the water infrastructure in the water-fragile country has become very crucial to reach a robust and resilient water sector which not only means providing the inhabitants with quantitatively sufficient and qualitatively healthy water but also aims to incorporate guaranteeing social, economic and political stability.

Changes of Extreme Events in Regional Climate Simulations over East Asia

Changes of extreme events due to greenhouse effects (2 × CO2) over East Asia, with a focus on the China region as simulated by a regional climate model (RegCM2), are investigated. The model is nested to a global coupled ocean-atmosphere model (CSIRO R21L9 AOGCM). Analysis of the control run of the regional model indicates that it can reproduce well the extreme events in China. Statistically significant changes of the events are analyzed. Results show that both daily maximum and daily minimum temperature increase in 2 × CO2 conditions, while the diurnal temperature range decreases. The number of hot spell days increases while the number of cold spell days decreases. The number of rainy days and heavy rain days increases over some sub-regions of China. The 2 × CO2 conditions also cause some changes in the tropical storms affecting China.

Amplitude modulation and extreme events in turbulent channel flow

Amplitude modulation of near-wall turbulence by large-scale structures in the outer layer is investigated by direct numerical simulation of turbulent channel flows at Reynolds number Re= 540, 1000, 2000. The effect of modulation is obvious in the two-point cross-section correlation map, and the correlation coefficients increase significantly with the Reynolds number. The influence of modulation is reflected in the tail of the probability density function of the near-wall flow signals, which expands as the Reynolds number increases. The flatness factor provides a quantitative description of the high fluctuation events due to modulation. Vortical structures associated with modulation are revealed by conditionally averaging the flow field of the near-wall extreme events, providing a depiction of how the influence of the large-scale structures penetrate towards the near-wall region.

Changes in Extreme Events as Simulated by a High-Resolution Regional Climate Model for the Next 20-30 Years over China

In this paper, the changes in temperature and precipitation extremes over the next 20-30 years (2021-2050) in relative to the present day (1986-2005) under the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A1B scenario are analyzed based on a high-resolution climate change simulation performed by a regional climate model (the Abdus Salam International Center for Theoretical Physics (ICTP) RegCM3). The extreme indices of summer days (SU), frost days (FD), and growing season length (GSL) for temperature and simple daily intensity index (SDII), number of days with precipitation ≥10 mm d-1 (R10), and consecutive dry days (CDD) for precipitation are used as the indicators of the extremes. The results show that the indices simulated by RegCM3 in the present day show good agreement with the observed. A general increase in SU, a decrease in FD, and an increase in GSL are found to occur in the next 20-30 years over China. A general increase in SDII, an increase in R10 over western China, and a decrease in R10 in north, northeast, and central China are simulated by the model. Changes in CDD are characterized by a decrease in the north and an increase in the south and the Tibetan Plateau.

Peaks over Manifold (POM): A Novel Technique to Analyze Extreme Events over Surfaces

We present a novel method to analyze extreme events of flows over manifolds called Peaks Over Manifold (POM). Here we show that under general and realistic hypotheses, the distribution of affectation measures converges to a Generalized Pareto Distribution (GPD). The method is applicable to floods, ice cover extent, extreme rainfall or marine heatwaves. We present an application to a synthetic data set on tide height and to real ice cover data in Antartica.

Workshop on Polar Climate Changes and Extreme Events

Polar climate systems have experienced a number of dramatic changes （Wang et al., 2017; Turner et al., 2016; Gordon, 2014; Rignot et al., 2013; Meier et al., 2012; Kwok and Rothrock, 2009; Thompson and Solomon, 2002）, which have influenced climatic conditions across large parts of the globe through large-scale atmospheric and oceanic teleconnections （Dou and Wu, 2018; Zhang et al., 2018;

Extreme Events Assessment Methodology Coupling Debris Flow,Flooding and Tidal Levels in the Coastal Floodplain of the Sao Paulo North Coast(Brazil)

The North Coastal Region of the State of S?o Paulo, which comprises the Municipalities of Caraguatatuba, S?o Sebasti?o, Ilhabela and Ubatuba, is one of the most prone to flooding and debris flow deposition Brazilian areas, owing to hydrological extreme rainfall events usually coupled with extreme tidal levels. This risk is also high due to human lives and material assets, with increasing population rates and the establishment of large companies such as the Oil industry, with reduced defense/prevention measures and works.The catastrophic scenario of the city of Caraguatatuba, in March 1967, resulting from one of the most serious natural disasters in Brazil, fosters discussions about probabilities of heavy rainfall-caused events and rise in the sea level in coastal areas. Hence, this research is a consequence of this reality. The research is founded on an innovative methodology based on the analysis of past data of rainfall and tidal stations, complemented with debris flow registers in the region of the north coastal zone of the State of S?o Paulo (Brazil). The anaysis developed involved the meteorological, hydraulic, geotechnical and statistical knowledge areas.Practical results are intended to be used for urban planning, designs of macro-drainage, fluvial, maritime projects and debris flow retention structures. These practical applications will then associate the probability of occurrence of certain types of heavy rainfall-caused events such as flooding or debris flow coupled with a corresponding increase in tidal levels.

Complex patterns of precipitation and extreme events during 1951-2011 in Sichuan Basin, Southwestern China

Sichuan Basin is located in southwestern China and affected by a complex water vapor （WV） sources. Here, the spatial and temporal patterns of precipitation and extreme events are investigated by six indices of World Meteorology Organization Commission, including annual precipitation total （AP）, maximum daily precipitation （Maxld）, intensity of rainfall over 1 mm/d （IR1）, maximum and mean consecutive dry days （Max CDD, Mean CDD） and coefficient of variance. Based on 24 daily precipitation time series from 1951 to 2o11, Mann-Kendall test is employed to quantify the significant level of these indices, from which the classification of precipitation change and its spatial patterns are obtained. Meanwhile, the probability distributions of these indices are identified by L-moment analysis and the Goodness-of-fit test, and the corresponding values are calculated by theoretical model at different return periods. The results reveal that the western basin displays normal drought： less AP and precipitation intensity while longer drought. The southern basin shows normal increase： larger AP and precipitation intensity but shorter CDD. However, in hilly region of the central basin and the transition zone between basin and mountains, precipitation changes abnormally： increasing both drought （one or both of Mean CDD and MaxCDD） and precipitation intensity （one or both of Maxld and trend of AP is. Probability IR1） no matter what the distribution models also demonstrate the complex patterns： a negative correlation between Maxld and Max CDD in the west （R2≥0.61） while a positive correlation in the east （R2≥0.41） at all return periods. These patterns are induced by the changes in WV sources and the layout of local terrain. The increase of WV in summer and decrease in spring leads to the heavier rainfall and longer drought respectively. The large heat island effect of the basin contributes to a lower temperature in transition zones and more precipitation in the downwind area. These results are helpful in reevaluating the risk regionally and making better decisions on water resources management and disaster prevention.

Analysis on Changes of Basic Climatic Elements and Extreme Events in Xinjiang, China during 1961-2010

By using the observation data from 89 weather stations in Xinjiang during 1961-2010, this paper analyzed the basic climatic elements including temperature, precipitation, wind speed, sunshine duration, water vapor pressure, and dust storm in the entire Xinjiang and the subareas: North Xinjiang, Tianshan Mountains, and South Xinjiang. The results indicate that from 1961 to 2010 the annual and seasonal mean temperatures in the entire Xinjiang show an increasing trend with the increasing rate rising from south to north. The increasing rate of annual mean minimum temperature is over twice more than that of the annual mean maximum temperature, contributing much to the increase in the annual averages. The magnitude of the decrease rate of low-temperature days is larger than the increase rate of high-temperature days. The increase of warm days and warm nights and the decrease of cold days and cold nights further reveal that the temperature increasing in Xinjiang is higher. In addition, annual and seasonal rainfalls have been increasing. South Xinjiang experiences higher increase in rainfall amounts than North Xinjiang and Tianshan Mountains. Annual rainy days, longest consecutive rainy days, the daily maximum precipitation and extreme precipitation events, annual torrential rain days and amount, annual blizzard days and amount, all show an increasing trend, corresponding to the increasing in annual mean water vapor pressure. This result shows that the humidity has increased with temperature increasing in the past 50 years. The decrease in annual mean wind speed and gale days lessen the impact of dust storm, sandstorm, and floating dust events. The increase in annual rainy days is the cause of the decrease in annual sunshine duration, while the increase in spring sunshine duration corresponds with the decrease in dust weather. Therefore, the increase in precipitation indicators, the decrease in gales and dust weather, and the increasing in sunshine duration in spring will be beneficial to crops growth.

Framework for Preventive Control of Power Systems to Defend Against Extreme Events

Enhancing power system resilience against extreme events is becoming increasingly critical. This paper discusses a unified framework for preventive control of power systems to enhance system resilience, which includes three parts: resilience assessment, resilience grading, and resilience enhancement. First, the resilience assessment contains facility-level and system-level resilience assessment. The concept of fragility curve is used in the facility-level resilience assessment. Various resilience indices are developed in system-level resilience assessment to roundly depict the impacts of extreme events on power systems and determine the system resilience. On this basis, the resilience is divided into different levels by resilience grading strategy, which can efficiently quantify the severity of the impact of extreme events and provide decision-making for the resilience enhancement strategies. Then, control strategies for enhancing power system resilience are also divided according to different resilience levels. A controlled islanding based preventive control is proposed to enhance system resilience, which aims to strengthen the first defensive line of power systems to deal with extreme events. Finally, taking the typhoon disaster in extreme events as an example, two tests carried out with two typhoons demonstrate the efficiency of the proposed method.

Coordinated Restoration Method for Electric Buses and Network Reconfigurations in Distribution Systems Under Extreme Events

Distribution systems are facing challenges in serving lifeline loads after extreme events.Network reconfiguration is a traditional and practical method for power supply restoration,which has strong but inflexible power transfer capabilities influenced by network topology.Multiple failures of utility power under extreme events will further limit the efficiency of network reconfiguration.Electric buses(EBs)can be utilized to achieve power supply considering their discharging capabilities as mobile storage devices.However,the mobility of EBs and the influences of transport systems must be carefully considered to enhance the resilience of distribution systems.Reconfiguration and EBs are complementary in terms of recovery capabilities and location flexibility,and more important loads can be recovered by the coordination between EBs and network reconfiguration.This paper proposes a coordinated restoration method for EBs and reconfigurations considering the influences of transport systems.The post-disaster restoration problem is formulated as a bi-level model,in which the network topology is optimized in the upperlevel aiming at maximizing restoration loads through the main grid and EBs,while the traffic paths of all EBs are optimized with the goal of maximizing the restoration loads by the EBs in the lower-level considering time consumption and energy consumption during movement.The PSO and a genetic algorithm are used to solve the proposed bi-level optimization problem.Simulation studies are performed to verify the superiority of the proposed method.

Assessing the Variability of Extreme Weather Events and Its Influence on Marine Accidents along the Northern Coast of Tanzania

The marine accidents are among the main components of the Zanzibar Disaster Management Policy (2011) and the Zanzibar Blue Economy Policy (2020). These policies aimed to institute legal frame works and procedures for reducing both the frequency of marine accidents and their associated fatalities. These fatalities include deaths, permanent disabilities and loss of properties which may result into increased poverty levels as per the sustainable development goal one (SDG1) which stipulates on ending the poverty in all its forms everywhere. Thus, in the way to support these Government efforts, the influence of climate and weather on marine accidents along Zanzibar and Pemba Channels was investigated. The study used the 10 years (2013-2022) records of daily rainfall and hourly wind speed acquired from Tanzania Meteorological Authority (TMA) (for the observation stations of Zanzibar, Pemba, Dares Salaam and Tanga), and the significant wave heights data, which was freely downloaded from Globally Forecasting System (GFS-World model of 13 km resolution). The marine accident records were collected from TASAC and Zanzibar Maritime Authority (ZMA), and the anecdotal information was collected from heads of quay and boat captains in different areas of Zanzibar. The Mann Kendal test, was used to determine the slopes and trends direction of used weather parameters, while the Pearson correlations analysis and t-tests were used to understand the significance of the underlying relationship between the weather and marine accidents. The paired t-test was used to evaluate the extent to which weather parameters affect the marine accidents. Results revealed that the variability of extreme weather events (rainfall, ocean waves and wind speed) was seen to be among the key factors for most of the recorded marine accidents. For instance, in Pemba high rainfall showed an increasing trend of extreme rainfall events, while Zanzibar has shown a decreasing trend of these events. As for extreme wind events, results show that Dar es Salaam and Tanga had an increasing trend, while Zanzibar and Pemba had shown a decreasing trend. As for the monthly variability of frequencies of extreme rainfall events, March to May (MAM) season was shown to have the highest frequencies over all stations with the peaks at Zanzibar and Pemba. On the other hand, high frequency of extreme wind speed was observed from May to September with peaks in June to July, and the highest strength was observed during 09:00 to 15:00 GMT. Moreover, results revealed an increasing trend of marine accidents caused by bad weather except during November. Also, results showed that bad weather conditions contributed to 48 (32%) of all 150 recorded accidents. Further results revealed significant correlation between the extreme wind and marine accidents, with the highest strong correlation of r = 0.71 (at p ≤ 0.007) and r = 0.75 (at p ≤ 0.009) at Tanga and Pemba, indicating the occurrence of more marine accidents at the Pemba channel. Indeed, strong correlation of r = 0.6 between extreme rainfall events and marine accidents was shown in Pemba, while the correlations between extremely significant wave heights and marine accidents were r = 0.41 (at p ≤ 0.006) and r = 0.34 (p ≤ 0.0006) for Pemba and Zanzibar Channel, respectively. In conclusion, the study has shown high influence between marine accidents and bad weather events with more impacts in Pemba and Zanzibar. Thus, the study calls for more work to be undertaken to raise the awareness on marine accidents as a way to alleviate the poverty and enhance the sustainable blue economy.

Extreme value theory applied to the auroral electrojet indices

The study of extreme weather and space events has gained paramount importance in modern society owing to rapid advances in high technology.Understanding and describing exceptional occurrences plays a crucial role in making decisive assessments of their potential impact on technical,economic,and social aspects in various fields.This research focuses on analyzing the hourly values of the auroral electrojet(AE)geomagnetic index from 1957 to 2019 by using the peak over threshold method in extreme value theory.By fitting the generalized Pareto distribution to extreme AE values,shape parameter indices were derived,revealing negative values that establish an upper bound for this time series.Consequently,it became evident that the AE values had reached a plateau,suggesting that extreme events exceeding the established upper limit are rare.As a result,although the need for diligent precautions to mitigate the consequences of such extreme events persists,surpassing the upper limit of AE values becomes increasingly challenging.It is also possible to observe an aurora in the middle-and low-latitude regions during the maximum period of the AE index.

Projected Changes in Extreme Event Indices for Alaska

As climate has warmed in recent decades, Alaska has experienced a variety of high-impact extreme events that include heat waves, wildfires, coastal storms and freezing rain. Because the warming is projected to continue, it is essential to consider future changes when planning adaptation actions and building resilience. In this study, we synthesize information on future changes in extreme events in Alaska from an ensemble of regional climate model simulations performed as part of Arctic-CORDEX (Coordinated Regional Climate Downscaling Experiment). A set of 13 extreme event indices, based on those developed by the World Climate Research Programme’s Expert Team on Climate Change Detection and Indices (ETCCDI), are evaluated from the Arctic-CORDEX output for Alaska. Of the 13 indices, six pertain to temperature, five to total precipitation, one to wind and one to snow. The results for locations in seven different climate zones of Alaska include large increases (5˚C - 10˚C) in the temperature thresholds for the five hottest and coldest days of the year, and large increases in warm spell duration and decreases in cold spell duration. Changes in the cold day temperature threshold are generally larger than the changes in the hot day temperature threshold, consistent with the projections of a stronger warming in winter than in summer in Alaska yearly maximum 1-day and 5-day precipitation amounts as well as the yearly number of consecutive wet days are projected to increase at all locations. The indices for heavy snow days and high-wind days show mixed changes, although the results indicate increases in heavy snow days at the more northern locations and increases in windy days at coastal locations. The changes in the extreme event indices continue through 2100 under the higher-emission (RCP 8.5) emission scenario, while the changes generally stabilize under the lower-emission (RCP 4.5) scenario. .

Understanding and Attribution of Extreme Heat and Drought Events in 2022: Current Situation and Future Challenges

Extreme weather events and their consequential impacts have been a key feature of the climate in recent years in many parts of the world,with many partly attributed to ongoing global-scale warming.The past year,2022,has been no exception,with further records being broken.The year was marked by unprecedented heatwaves and droughts with highly unusual spatial extent,duration and intensity,with one measure indicating an aggregated and overall intensity of extreme heat events worldwide not seen since at least 1950.The extreme drought measured by surface soil moisture covered 47.3%of global land areas in 2022,which was the second most widespread year since 1980.Here,we examine notable events of the year in five major regions of the world:China’s Yangtze River region,western Europe,the western U.S.,the Horn of Africa and central South America.For each event,we review the potential roles of circulation,oceanic forcing(especially the“triple-dip”La Niña)and anthropogenic climate change,with an aim of understanding the extreme events in 2022 from a global perspective.This will serve as a reference for mechanism understanding,prediction and attribution of extreme events.

A Statistical Linkage between Extreme Cold Wave Events in Southern China and Sea Ice Extent in the Barents-Kara Seas from 1289 to 2017

Arctic sea ice loss and the associated enhanced warming has been related to midlatitude weather and climate changes through modulate meridional temperature gradients linked to circulation. However, contrasting lines of evidence result in low confidence in the influence of Arctic warming on midlatitude climate. This study examines the additional perspectives that palaeoclimate evidence provides on the decadal relationship between autumn sea ice extent (SIE) in the Barents-Kara (B-K) Seas and extreme cold wave events (ECWEs) in southern China. Reconstruction of the winter Cold Index and SIE in the B-K Seas from 1289 to 2017 shows that a significant anti-phase relationship occurred during most periods of decreasing SIE, indicating that cold winters are more likely in low SIE years due to the “bridge” role of the North Atlantic Oscillation and Siberian High. It is confirmed that the recent increase in ECWEs in southern China is closely related to the sea ice decline in the B-K Seas. However, our results show that the linkage is unstable, especially in high SIE periods, and it is probably modulated by atmospheric internal variability.

Multiscale Combined Action and Disturbance Characteristics of Pre-summer Extreme Precipitation Events over South China

The dominant frequency modes of pre-summer extreme precipitation events(EPEs)over South China(SC)between1998 and 2018 were investigated.The 67 identified EPEs were all characterized by the 3-8-d(synoptic)frequency band.However,multiscale combined modes of the synoptic and three low-frequency bands[10-20-d(quasi-biweekly,QBW);15-40-d(quasi-monthly,QM);and 20-60-d(intraseasonal)]accounted for the majority(63%)of the EPEs,and the precipitation intensity on the peak wet day was larger than that of the single synoptic mode.It was found that EPEs form within strong southwesterly anomalous flows characterized by either lower-level cyclonic circulation over SC or a deep trough over eastern China.Bandpass-filtered disturbances revealed the direct precipitating systems and their life cycles.Synoptic-scale disturbances are dominated by mid-high latitude troughs,and the cyclonic anomalies originate from downstream of the Tibetan Plateau(TP).Given the warm and moist climate state,synoptic-scale northeasterly flows can even induce EPEs.At the QBW and QM scales,the disturbances originate from the tropical Pacific,downstream of the TP,or mid-high latitudes(QBW only).Each is characterized by cyclonic-anticyclonic wave trains and intense southwesterly flows between them within a region of large horizontal pressure gradient.The intraseasonal disturbances are confined to tropical regions and influence SC by marginal southwesterly flows.It is concluded that low-frequency disturbances provide favorable background conditions for EPEs over SC and synoptic-scale disturbances ultimately induce EPEs on the peak wet days.Both should be simultaneously considered for EPE predictions over SC.

Moisture Transport and Associated Background Circulation for the Regional Extreme Precipitation Events over South China in Recent 40 Years

Based on the hourly precipitation data at 176 observational stations over south China and the hourly ERA5reanalysis data during the 40-yr period of 1981-2020, we analyzed the universal characteristics of moisture transport and their associated background circulations for four types of regional extreme precipitation events(REPEs) over south China. Main findings are shown as follow.(i) The wind that transported moisture for the REPEs over south China featured a notable diurnal variation, which was consistent with the variations of the precipitation.(ii) Four types of REPEs could be determined, among which the southwest type(SWT) and the southeast type(SET) accounted for ~92%and ~5.7%, respectively, ranking the first and second, respectively.(iii) Trajectory analyses showed that the air particles of the SWT-REPEs had the largest specific humidity and experienced the most intense ascending motion, and therefore their precipitation was the strongest among the four types.(iv) South China was dominated by notable moisture flux convergence for the four types of REPEs, but their moisture transport was controlled by different flow paths.(v)Composite analyses indicated that the background circulation of the four types of REPEs showed different features,particularly for the intensity, location and coverage of a western Pacific subtropical high. For the SWT-REPEs, their moisture transport was mainly driven by a lower-tropospheric strong southwesterly wind band in the low-latitude regions. Air particles for this type of REPEs mainly passed over the Indochina Peninsula and South China Sea. For the SET-REPEs, their moisture transport was mainly steered by a strong low-tropospheric southeasterly wind northeast of a transversal trough. Air particles mainly passed over the South China Sea for this type of REPEs.