Mechanism and forecasting method of persistent extreme weather events: review and prospect

Persistent extreme weather is of high disaster causing capability, represents a great threat to the safety of both people and property and results in substantial economic losses. However, the underlying mechanism of such high impact weather remains unclear, and related forecasting methods are quite under studied currently. Based on the comprehensive reviews of the relevant studies about persistent extreme weather, the prediction of such events within the period during 1～2 weeks in advance is believed to be a significant scientific issue. For this scientific problem, the studies of atmospheric low frequency process, the interaction between multi scale systems, the forcing of complicated underlying surface and sea land atmosphere interactions are necessary to be performed. These multi perspective studies will favor the final establishment of the corresponding forecasting theory and method based on the combination of dynamical prediction and statistical predication. It is hoped that the deficiencies in systematic studies about persistent extreme weather may be made up through pertinent studies, which will prolong the time length of forecasting and increase the prediction precision of such high impact events.     

The impact of extreme weather and climate change on inland waterway transport

Similarly to other modes of transport, inland waterway transport has to deal with weather events, affecting navigation conditions and the infrastructure on inland waterways. Most significant extreme weather events result from high precipitation, droughts and temperatures below zero degrees Celsius. Heavy rainfall, in particular in association with snow melt, may lead to floods resulting in suspension of navigation and causing damage to the inland waterway infrastructure as well as the property and health of human beings living in areas exposed to flooding. Long periods of drought may lead to reduced discharge and low water levels, limiting the cargo-carrying capacity of vessels and increasing the specific costs of transportation. Temperatures below zero degrees Celsius over a longer period may cause the appearance of ice on waterways, leading to suspension of navigation and possible damage to infrastructure, for example, buoys. Neither extreme weather events as well as climate change are new phenomena nor is their general occurrence expected to change suddenly. However, due to climate change, extreme weather events may change positively or adversely in severity and frequency of occurrence, depending on the respective weather event and the location of its occurrence. This paper gives an overview of the impact of extreme weather events on inland waterway transport in Europe, focussed on the Rhine–Main–Danube corridor, followed by a discussion on how climate change will change these events and their impacts.     

The extreme weather risk indicators (EWRI) for the European transport system

The European 7th Framework Programme project Extreme Weather impacts on European Networks of Transport devised a holistic analysis of extreme weather risks for the transport system. The analysis provided an overview of extreme weather risks, or a risk panorama. The risk panorama was built on a probabilistic approach to extreme weather phenomena occurrences and on vulnerability analysis based on selected macro-level economic and transport system indicators of the member states of EU-27. The panorama covers all transport modes and views infrastructure-related risks, time delay risks, and accidents risks. In addition to climatic circumstances, the devised risk indicator is also dependent on regional circumstances, such as population and transport density and income level. This paper describes the construct and application of an extreme weather risk indicator (EWRI). EWRIs are counted for each country and each transport mode separately. Furthermore, this paper also presents the most significant extreme weather events in different parts of Europe and on the transport modes they affect the most.     

Severe weather affecting European transport systems: the identification,classification and frequencies of events

Severe weather can have serious repercussions in the transport sector as a whole by increasing the number of accidents, injuries and other damage, as well as leading to highly increased travel times. This study, a component of the EU FP7 Project EWENT, delineates a Europe-wide climatology of adverse and extreme weather events that can be expected to affect the transport network. We first define and classify the relevant severe weather events by investigating the effects of hazardous conditions on different transportation modes and the infrastructure. Consideration is given to individual phenomena such as snowfall, heavy precipitation, heat waves, cold spells, wind gusts; a combined phenomenon, the blizzard, is also considered. The frequency of severe weather events, together with the changes in their spatial extension and intensity, is analyzed based on the E-OBS dataset (1971–2000) and the ERA-Interim reanalysis dataset (1989–2010). Northern Europe and the Alpine region are the areas most impacted by winter extremes, such as snowfall, cold spells and winter storms, the frequency of heavy snowfall. The frequency of hot days is highest in Southern Europe. Severe winds and blizzards are the most common over the Atlantic and along its shores. Although heavy rainfall may affect the whole continent on an annual basis, extreme precipitation events are relative sparse, affecting particularly the Alps and the Atlantic coastline. A European regionalization covering similar impacts on the transport network is performed.     

The influence of episodic weather events on tidal residual currents: A case study at Sebastian Inlet,Florida

Field data of tidal current speeds collected January 9–31, 1990, in Sebastian Inlet, which connects the Atlantic Ocean and the Indian River Lagoon on the east coast of central Florida, show that the average Eulerian and Stokes residual currents are both lagoonward. This pattern can be used to explain the long-term trend of accumulations of marine sediments on the flood tidal delta adjacent to the lagoon end of the inlet. Numerical model results indicate that the long-term Stokes residual current is mainly determined by the tidal characteristics of the lagoon and ocean, and subsequently, are less variable. The long-term lagoonward Eulerian current, on the other hand, is interrupted by episodic weather events such as frontal storms. Storms can cause the abrupt superelevation of instantaneous water-levels on the lagoon side of the inlet. The short-lived pulses of freshwater inflow into the lagoon associated with storms could be discharged through the inlet instantaneously. Both the instantaneous superelevation of lagoon water levels and freshwater outflow can cause temporary reversal of Eulerian residual current in the inlet. Therefore, the general residual flow pattern in Sebastian Inlet is not only determined by the tidal characteristics of the Atlantic Ocean and Indian River Lagoon but also by the wind and precipitation associated with episodic storms, and by the long-term mean sea-level difference between the lagoon and the ocean.     

Variability in the characteristics of extreme rainfall events triggering debris flows: a case study in the Chenyulan watershed,Taiwan

Natural Hazards - This work examines the period affected by extreme rainfall that triggers debris flow and the modification of the critical rainfall threshold for debris flows after extreme events...     

Optimizing the location of aerial resources to combat wildfires: a case study of Portugal

Natural Hazards - Wildfires are becoming larger and more severe in different regions of the world as a result of climate change. A successful wildfire response requires a strong initial attack to...     

Evaluation of environmental fate and sinks of PCDD/Fs during specific extreme weather events in Taiwan

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are persistent organic pollutants (POPs) that are formed and released unintentionally from anthropogenic sources. The high persistence of PCDD/Fs results in the concentrations of these contaminants in environment decreasing only very slowly. Two transport pathways, air and water, carry PCDD/Fs into all regions of the world. Recently, more frequent extreme weather events, such as storms and floods, have been projected to occur as a result of global warming. Extreme weather events have a documented impact on the remobilization and subsequent bioavailability of POPs. In this study, three specific episodes, namely winter monsoon, southeast biomass burning and tropical cyclone (typhoon) events, which influence the environmental fate and transport of PCDD/Fs in Taiwan, were evaluated based on a climate change scenario. During the winter (northeast) monsoon period, the temperature and relative humidity observed in northern Taiwan decreases sharply. During this time, the quantity of PCDD/Fs adsorbed onto suspended particles, as observed at background sites, was found to increase from 300 ± 127 to 630 ± 115 pg I-TEQ g-TSP⁻¹, which is even higher than that measured in Taipei City (438 ± 80 pg I-TEQ g-TSP⁻¹). Hence, the winter monsoon not only brings cold air but also transports air pollutants and dust over long distances from mainland China to Taiwan. During the 2010 Southeast Asia biomass burning events (2010/3/22–3/28), the level of atmospheric PCDD/Fs were measured in central Taiwan (Mt. Lulin) and in the source region of northern Thailand (Chiang Mai); this revealed that the variations in atmospheric PCDD/F concentrations at these two sites followed a similar pattern. On 25 March 2010, the atmospheric PCDD/F concentration increased dramatically from 1.43 to 6.09 fg I-TEQ m⁻³ at Mt. Lulin and from 7.64 to 12.1 fg I-TEQ m⁻³ in northern Thailand. However, the atmospheric PCDD/F concentration decreased dramatically 1 day after the biomass burning event. Based on the measurements from a dated sediment core collected at a reservoir in northern Taiwan, the sharp increases in input fluxes of PCDD/Fs and mineral-derived elements levels in 1990 (20 ng I-TEQ m⁻² year⁻¹), 2001 (17 ng I-TEQ m⁻² year⁻¹), 2004 (16 ng I-TEQ m⁻² year⁻¹) and 2005 (15 ng I-TEQ m⁻² year⁻¹) seem to be a result of a deep turbid layer formed upstream due to landslides and/or mud flows during the typhoon season. This finding demonstrates the effect of typhoon events on the long-term remobilization of PCDD/Fs as well as supporting the hypothesis that such events would have the potential to remobilize pollutants that have been deposited previously.     

石笋记录年际、年代际极端天气/气候事件研究进展

近年来随着极端天气/气候事件的频发,应对极端天气/气候事件的要求极其紧迫。目前气象资料对极端天气/气候事件的研究相对较短,由此作者提出利用石笋记录重建历史年际、年代际极端天气/气候事件的构想。通过对目前已有的石笋极端天气/气候事件研究实例分析总结,认为洞穴石笋沉积速率相对较快,石笋中标志性结构构造特征的存在,有利于石笋记录到极端天气/气候事件。同时就目前的研究现状,作者提出建立准确年代标尺、选择生长速率相对较快和存在标志性结构构造特征、能记录到极端气候的石笋,以及提高采样分辨率和与其他记录相互验证等作为石笋极端气候研究的工作要求,同时就文石笋研究极端天气/气候事件提出文石笋可能更加容易记录到极端天气/气候事件的个人新认识。     

石笋记录年际、年代际极端天气/气候事件研究进展

近年来随着极端天气/气候事件的频发,应对极端天气/气候事件的要求极其紧迫。目前气象资料对极端天气/气候事件的研究相对较短,由此作者提出利用石笋记录重建历史年际、年代际极端天气/气候事件的构想。通过对目前已有的石笋极端天气/气候事件研究实例分析总结,认为洞穴石笋沉积速率相对较快,石笋中标志性结构构造特征的存在,有利于石笋记录到极端天气/气候事件。同时就目前的研究现状,作者提出建立准确年代标尺、选择生长速率相对较快和存在标志性结构构造特征、能记录到极端气候的石笋,以及提高采样分辨率和与其他记录相互验证等作为石笋极端气候研究的工作要求,同时就文石笋研究极端天气/气候事件提出文石笋可能更加容易记录到极端天气/气候事件的个人新认识。     

The role of extreme events in evolution

Evolutionists have often had a marked tendency to think that, in the course of time, planetary events were not very different from those occurring during a human life. However, when a ‘non-human’ timescale is used, the history of our planet appears profoundly and frequently disturbed by extreme events. These events, even not always instantaneous, impose – because of their amplitude – a severe sorting, not between individuals of a species, but between species, or even between phyla. In the face of an extreme event, intraspecific diversity counts little: it is the interspecific diversity that makes the difference. As shown by mass extinctions, extreme events open ecological niches and redistribute the cards of life, giving survivors opportunities to radiate. The capacity to cope with extreme ecological conditions favours certain species in ecosystems, not certain individuals in populations. This is not a macroevolutionary process in terms of acquiring new adaptations, but a macroevolutionary process in terms of sorting entire sections of life. The most important is perhaps that the current ‘mediatisation’ of a limited number of mass extinctions dissimulates less important extinctions caused by less extreme and more localized events that were possibly responsible for many changes in the composition and structure of communities throughout the evolution. The term of ‘pre-adaptation’ has been neglected, because it gives an impression of finalism, but it expresses well that, when an unexpected event occurs, a particular species has or has not the ‘right genes’ to continue to sustain viable populations. The role of extreme events in modifying the course of evolution should not be underestimated.     

Freezing rain events: a major weather hazard in the conterminous US

Freezing rain (FZRA) is well documented as a major weather hazard, producing damage to structures, the environment, and humans, and delaying various operations such as transportation. Assessing the risk of freezing rain events requires information for various areas of the nation about the frequency, duration, and intensity of these events along with the associated weather conditions that affect the damage caused by freezing rain. This includes temperatures (dry and wet bulb), the amount of precipitation, and winds during freezing rain. The purpose of this work was to develop a national and regional climatology of freezing rain events in the US for the period of 1928–2001 to addresses these conditions.     

Assessment of the availability of near-real time open weather data provided by networks of surface stations in Spain

The aims of this research are: (i) to check availability of weather observations from automated stations in Spain, (ii) to qualitatively and quantitatively describe the networks identified, (iii) to analyze availability of the observations gathered for 3 different networks [two government (GOV): AEMET with national coverage and CASTILLA Y LEÓN on a regional level; and METEOCLIMATIC, a network of volunteer weather observation (VWO) stations on a national level], and (iv) to undertake a spatial redundancy and lacunarity analysis of them. The results reveal: the existence of heterogeneous VWO networks complementing the GOV, differences within and among networks as far as data acquisition frequency, varying delays in their publication, and semantic differences in the observations made. An inventory was made of 24 networks (16 GOV and 8 VWO) with 3,908 stations deployed in Spain. An analysis of observations from 3 networks reveals that 88 % of the stations in the volunteer network record more than two observations per hour. 56 % of the AEMET stations report more than 48 observations every day, 31 % report between 25 and 48 observations a day. Conversely, the CASTILLA Y LEÓN network records data every half hour. The redundancy analysis reveals a 3,429-drop in the number of unduplicated stations. Following the lacunarity analysis of spatial distribution, it is possible to conclude that 60.72 % of the cells do not contain any stations.     

Simulation of high-impact tropical weather events: comparative analysis of three heavy rainfall events

Episodes of heavy rainfall, although relatively rare, significantly contribute to the hydrological cycle due to the large quantum of rainfall in a short span of time. Accurate simulation of such heavy or extreme rainfall events therefore is an important benchmark for a model. Here, we consider the simulation of three heavy rainfall events (Mumbai, Bangalore and Chennai) that occurred over the Indian monsoon region in different geographical locations and seasons during 2005, using a mesoscale meteorological model, namely MM5V3. Simulations have been carried out at high resolution (2 km) to resolve orographic features and land–ocean gradients over the event locations with a 3-nest, 2-way configuration. The primary objective of this study is to carry out a multi-event, multi-location evaluation of the model configuration for simulating a class of heavy rainfall events and to compare some important meteorological features of the events. Our results have shown that a very high relative humidity, low-level convergence, convective instability in terms of equivalent potential temperature, high vertical velocity, smaller mixing ratio at low level and higher mixing ratio at upper level essentially dominated and sustained the convective dynamics in all the three events. It was also found that the latent heat flux (LHF) dominated coastal events (Mumbai and Chennai) with relatively much higher values compared to sensible heat flux (SHF) throughout the event life cycle. In the case of the Bangalore event, both LHF and SHF are comparable during the event life cycle.     

Research frontiers in climate change: Effects of extreme meteorological events on ecosystems

Climate change will increase the recurrence of extreme weather events such as drought and heavy rainfall. Evidence suggests that modifications in extreme weather events pose stronger threats to ecosystem functioning than global trends and shifts in average conditions. As ecosystem functioning is connected with ecological services, this has far-reaching effects on societies in the 21st century. Here, we: (i) present the rationale for the increasing frequency and magnitude of extreme weather events in the near future; (ii) discuss recent findings on meteorological extremes and summarize their effects on ecosystems and (iii) identify gaps in current ecological climate change research.     

我国新疆北部地区夏季极端降水事件的特征分析

基于1961 - 2017年6 - 8月新疆北部47个观测站点的逐日降水资料, 根据百分位法定义不同站点的夏季极端降水阈值, 分析了新疆北部地区夏季极端降水事件和最大日降水的时空分布特征、 贡献率及其与海拔的关系。结果表明： 新疆北部地区夏季极端降水事件和最大日降水量的各个特征量分布存在明显的时空差异, 空间上夏季极端降水事件、 最大日降水量表现为山区高、 盆地低的特点,在海拔2 000 m左右存在一个最大降水带; 夏季极端降水事件和最大日降水量呈增多、 增强的趋势, 并从20世纪90年代前后开始有明显的增加。夏季极端降水事件主要以单日为主, 夏季极端降水贡献随时间呈缓慢增加的趋势, 而夏季极端降水过程贡献和最大日降水贡献随时间变化呈下降趋势。     

Adapting rail and road networks to weather extremes: case studies for southern Germany and Austria

The assessment of the current impacts of extreme weather conditions on transport systems reveals high costs in specific locations. Prominent examples for Europe are the economic consequences of the harsh winter periods 2009/2010 and 2010/2011 and the floods in Austria, Eastern Europe, Germany and the United Kingdom in 2005 and 2007. Departing from the EC-funded project WEATHER, this paper delves into the subject of adaptation strategies by revisiting the project’s general findings on adaptation strategies and by adding two specific cases: (1) advanced winter maintenance on roads in southwest Germany and (2) technical and organizational measures in Alpine rail transport. For these two cases, feasible adaptation strategies are elaborated and their potential is discussed in light of damage cost forecasts up to 2050. For the road sector, we find a high potential to mitigate weather-related costs, although damages here are expected to decline. In contrast, rail systems face strongly increasing damages and the mitigation options offered by improved information and communication systems seem to be largely exploited. Consequently, it is easier to justify expensive adaptation measures for high-cost rail infrastructures than for road transport. A generic analysis of 14 damage cases worldwide, however, revealed that generally awareness raising, cooperation and communication strategies are sufficient to mitigate the most severe damages by natural disasters.