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1.
全球变暖背景下,偶发极端冷事件产生的重大灾害损失不容忽视。探究区域极端冷事件的大尺度驱动因子的耦合影响,对预估和应对气候变化产生的极端灾害具有重要意义。本文基于新疆1961—2016年53个气象站点的逐日气温资料,通过反距离加权等方法对极端冷事件的时空演变特征进行分析;利用交叉小波变换对6个极端冷指数与大尺度驱动因子——北极涛动（AO）、北大西洋涛动（NAO）和厄尔尼诺-南方涛动（ENSO）进行多尺度分析;使用参数假设检验对大尺度驱动因子单一/耦合模态下的冷指数变化进行统计学显著性检验,随后对大尺度环流机制进行距平合成分析。结果表明：年均冷指数在时间尺度上均有显著性变化,新疆气温有明显的变暖趋势;空间尺度上冷指数在北疆、东疆和伊犁河谷地区的变化幅度远大于其他区域,存在空间差异性。AO、NAO与冷指数的相关性较强,ENSO与冷指数相关关系最弱但存在明显的时滞效应,大尺度驱动因子对极端冷指数的总体影响程度为AO>NAO>ENSO。单一模态下,极端冷事件在AO负位相、NAO负位相和La Ni?a事件期间易发生。耦合模态下,EI Ni?o-AO正位相和EI Ni?o-NAO正位相配置下冷日日数偏多;EI Ni?o-NAO负位相配置时极端低温值更小;La Ni?a-AO负位相和La Ni?a-NAO正位相时极端冷事件发生的可能性更大。EI Ni?o（La Ni?a）事件对AO（NAO）有一定的调制作用。新疆极端冷事件更易出现在La Ni?a-AO负位相、La Ni?a-NAO正位相时期,成因与亚欧大陆中高纬度位势异常导致冷空气路径偏西、乌拉尔阻塞加强与偏北气流影响新疆有关。 相似文献
2.
The Influence of the North Atlantic Oscillation on Rainfall Triggering of Landslides near Lisbon 总被引：1，自引：0，他引：1
The majority of landsliding episodes in the area north of Lisbon are associated with rainfall events of short (less than 5
days) medium (5–20 days) or long duration (more than 20 days). The precipitation regime in Portugal is highly irregular, with
large differences between wet and dry years. We have assessed the impact of the North Atlantic Oscillation (NAO) on both the
winter precipitation and the timing and magnitude of associated landslide events. Results show that the large inter-annual
variability of winter precipitation is largely modulated by the NAO mode. The precipitation composite corresponding to high
NAO index presents a considerable lower median value (47 mm/month) than the corresponding low NAO index class (134 mm/month).
The entire precipitation distribution associated with the low NAO index composite encompasses a wider range of values than
the corresponding high NAO index composite. This non-linear behavior is reflected in the probability of occurrence of a very
wet month (precipitation above the 90% percentile) that is just 1% for the positive NAO class and 23% for low NAO index months.
Results for the low NAO class are crucial because these months are more likely associated with long-lasting rainfall episodes
responsible for large landslide events. This is confirmed by the application of a 3-month moving average to both NAO index
and precipitation time series. This procedure allowed the identification of many months with landslide activity as being characterized
by negative average values of the NAO index and high values of average precipitation (above 100 mm/month). Finally, using
daily data we have computed the return periods associated with the entire set of landslide episodes and, based on these results,
obtained a strong linear relationship between critical cumulative rainfall and the corresponding critical rainfall event duration. 相似文献
3.
Analysis of two continuous, high‐resolution palaeo‐flood records from southern Norway reveals that the frequency of extreme flood events has changed significantly during the Holocene. During the early and middle Holocene, flood frequency was low; by contrast, it was high over the last 2300 years when the mean flood frequency was about 2.5–3.0 per century. The present regional discharge regime is dominated by spring/summer snowmelt, and our results indicate that the changing flood frequency cannot be explained by local conditions associated with the respective catchments of the two lakes, but rather long‐term variations of solid winter precipitation and related snowmelt. Applying available instrumental winter precipitation data and associated sea‐level pressure re‐analysis data as a modern analogue, we document that atmospheric circulation anomalies, significantly different from the North Atlantic Oscillation (NAO), have some potential in explaining the variability of the two different palaeo‐flood records. Centennial‐scale patterns in shifting flood frequency might be indicative of shifts in atmospheric circulation and shed light on palaeo‐pressure variations in the North Atlantic region, in areas not influenced by the NAO. Major shifts are found at about 2300, 1200 and 200 years ago (cal. a BP). Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
4.
The North Atlantic Oscillation (NAO) is one of the modes of climate variability in the North Atlantic region. The atmospheric circulation during the winter season in this region commonly displays a strong meridional (north–south) pressure contrast, with low air pressure (cyclone) centred close to Iceland and high air pressure (anticyclone) near the Azores. This pressure gradient drives the mean surface winds and the mid‐latitude winter storms from west to east across the North Atlantic, bringing mild moist air to northwest Europe. The NAO index is based on the difference of normalised sea‐level pressures (SLP) between Ponta Delgada, Azores and Stykkisholmur, Iceland. The SLP anomalies at these stations are normalised by division of each monthly pressure by the long‐term (1865–1984) standard deviation. Interannual atmospheric climate variability in northwest Europe, especially over Great Britain and western Scandinavia has, during the last decades, been attributed mainly to the NAO, causing variations in the winter weather over the northeast North Atlantic and the adjacent land areas. A comparison between the NAO index and the winter (December–March) precipitation between ad 1864 and 1995 in western Norway shows that these are strongly linked (correlation coefficient 0.77). Variations in the NAO index are also reflected in the mass balance records of glaciers in western Scandinavia. The NAO index is best correlated with mass balance data from maritime glaciers in southern Norway (e.g. Ålfotbreen R2 = 0.51). The record of Holocene (last ca. 11 500 cal. yr) glacier variations of maritime glaciers in western Scandinavia is thus a proxy of pre‐instrumental NAO variations. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
5.
Extreme weather events present environmental and social challenges across the Eurasian steppe. In Mongolia much attention is given to drought and dzud (severe winter conditions) impact on rural livelihoods, landscapes and governance. A link between the two events, fostered by international and state agencies, speculates that drought leads to dzud; this has become the widely accepted doctrine. However, the relationship between the two events is assumed rather than analysed. Whilst there may be natural links between climate events, causality is more difficult to establish yet often claimed post-event. This paper stresses Mongolia’s destructive dzuds of 1999–2001 and 2009–2010 in examining drought frequency before dzud events. Findings question the hazard connection as just 3 of 32 examined dzud events were preceded by drought. Investigation did not document a relationship between the disasters; linkages between extreme events were implied rather than established. The human role in disaster also needs to be assessed as preparation, and response are key factors for mitigation. Study results identified a lack of causality between the disasters, suggesting more assiduous investigation of hazards is needed in Mongolia. This can clarify causal factors, identify risk and improve disaster mitigation strategies in Mongolia. 相似文献
6.
利用历史文献记录重建了公元1000—2000年中国北方地区极端干旱事件序列,在此基础上分析极端干旱事件的发生特征与规律。研究得出以下结论:(1)极端干旱事件在公元1000—2000年中存在200年左右的周期波动。在15世纪中期、17世纪初期和18世纪末期存在3次极端干旱事件高发期。(2)极端干旱事件的变动与中国东部地区干湿变化相一致,在偏干的时期极端干旱事件发生次数上升,在偏湿时则下降。(3)在中世纪暖期和现代暖期,温度愈高,极端干旱事件偏多;而在小冰期,则温度偏低的时期极端干旱事件多发。(4)西风带影响下的非季风区,干湿变化与极端干旱事件的关系与华北季风区相反,这可能与所谓的“丝绸之路遥相关”和NAO(NorthAtlanticOscillation,北大西洋涛动)的影响有关。 相似文献
7.
8.
卫星遥感首次监测到准噶尔盆地西北部的冬季融雪洪水 总被引：1，自引：0，他引：1
2010年1月,新疆北部出现了多次寒潮和60a一遇的连续暴雪天气.在此期间,准噶尔盆地西北部的裕民县及其邻近地区2010年1月6日出现了融雪型洪水.2010年1月裕民降雪量高达95mm,较历年同期偏多5.8倍,突破历史极值;2010年1月1—20日裕民日平均气温均方差达6.5℃,气温升降剧烈,变化幅度大.通过EOS/MODIS卫星遥感监测发现,2010年1月5日裕民县及其邻近地区地表有明显成片的液态水痕迹,而在其前后时段该地区为积雪覆盖.2010年1月,裕民县出现极端降雪事件的同时,极端暖事件与极端冷事件交替出现,隆冬时节的异常升温造成阶段气温异常偏高,引发冬季融雪型洪水.气候变暖背景下,需加强对新疆区域极端天气气候事件的监测、分析及其形成机理的研究,加强区域气候变化影响评估工作,采取切实可行的措施应对气候变化. 相似文献
9.
用1995年5月至1999年4月KWBC北半球500 hPa高度场5°×5°客观分析资料,应用谐波分析把等压面高度场沿纬圈作富利叶级数展开,计算逐日25°~80°N每隔5°纬度递增的沿纬圈的扰动动能与平均动能转换率(E)、角动量涡旋输送(RM),分析了E和RM的年、季分布特征及其与新疆暴风雪过程的关系.结果表明:E和RM具有显著的季节变化和周期性;E的正高值中心与新疆暴风雪过程有较好的关系,出现E正高值中心的日期作为预报指标日,其后3~6 d新疆将出现暴风雪天气过程,出现RM负低值中心的日期作为预报指标日,其后3~8 d新疆有暴风雪过程发生;当E的正高值中心和RM的负值中心同时出现时,更确定了新疆暴风雪过程出现的可能性. 相似文献
10.
暴雪是冬季雪灾发生的主因,气候变化导致极端天气气候事件频繁发生,准确预报暴雪天气过程对防灾减灾起着重要作用. 以内蒙古锡林郭勒盟地区2012年11月3-5日出现的一次暴雪天气过程为例,对2012年锡林郭勒盟地区冬季出现的暴雪天气过程进行了诊断分析. 结果表明：暴雪天气过程的主要环流背景条件是乌拉尔山长脊和西伯利亚冷涡,而高空蒙古低槽、低空切变线和地面河套气旋是这次暴雪的触发机制. 此次暴雪天气属于强冷空气类蒙古低槽(涡)型,发生在高湿区和水汽通量辐合区内,地面气旋和华北脊对暴雪的产生和落区起到决定性作用. 暴雪天气从降雪前期到结束,整层湿层较深厚,低空急流的建立为暴雪提供了很好的不稳定能量和水汽辐合条件,锡林郭勒盟地区有高空辐散低空辐合强烈的上升运动,为此次暴雪提供了非常有利的动力条件. 乌拉尔山高压脊东移,使强冷空气沿脊前西北气流南下,地面气旋不断发展,而南方暖湿气流强盛,迫使气旋东移;华北脊的阻挡作用使得气旋缓慢移动,影响系统滞留于锡林郭勒盟地区,产生长时间的降雪天气. 相似文献
11.
Eighty-two-year rainfall time series have been studied together with climatic patterns of NAO using classical statistical methods. Then, the wavelet approach has been applied to show annual (1 year (1y)) and inter-annual (2–4 years (2-4y), 5–8 years (5-8y), and 8–16 years (8-16y)) modes distributed following four major discontinuities: 1945, 1960, 1975, and 1995. The 1y, 2-4y, and 5-8y powers show high energy during the wet period 1922–1930 and a low one in 1928–1938. After 1945, the annual mode highlights a high energy while the inter-annual modes present low energy. Between 1975 and 1995, powerful modes of 1 and 2–4 years are identified with low power of 5-8y and 8-16y modes. Since 1995, the low power of 5–8y decreases, while the 8-16y mode emphasizes a high variability. The coherence between NAO and Marrakech precipitation is strongly defined for low frequencies with a total contribution of 75 %. This coherence is in phase in the beginning and presents out phase signs since 1945. The change of phase can be associated to a decreasing of coherence especially around 1990. This finding is useful to understand the relationship between the hydrological variability and NAO climate patterns in the southern side of the Mediterranean Sea. 相似文献
12.
Juha Schweighofer 《Natural Hazards》2014,72(1):23-40
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. 相似文献
13.
Bilel Zerouali Mohamed Mesbah Mohamed Chettih Mohammed Djemai 《Arabian Journal of Geosciences》2018,11(14):392
This paper is proposed for the investigation of possible relationships between the large-scale atmospheric circulation phenomena such as the North Atlantic Oscillation (NAO), Southern Oscillation (SOI), Mediterranean Oscillation (MO), Western Mediterranean Oscillation (WeMO) and rainfall of Sebaou river watershed (Northern central Algeria), covering a period of 39 years at monthly scale. Several time and scale-based methods were used: correlation and spectral analysis (CSA), continuous wavelet transform (CWT), multiresolution wavelet analysis (MRWA), cross wavelet analysis (XWT), wavelet coherence transform (WCT) and cross multiresolution wavelet analysis (CMRWA). The rainfall analysis by CSA and CWT has been clearly demonstrating the dominance of 1 year and 1–3-year modes, which they explain 30 to 51% and 25 to 28% of the variance respectively. However, the indices have shown that inter-annual fluctuations up to long-term explain between 60 and 90%. CWT and MRWA indicated significant fluctuations materialising a dry period more marked between the 1980s and 1990s with strong trend towards drier conditions starting from the 1980s, explained by the decadal components D7 and the approximation A7. In addition to the annual component, the XWT spectrums reveal strong coefficients for the SOI between 1992–2005 and 1986–2000 for the modes of 5–10 years and higher than 10 years respectively and less intense for NAO. The WCT between NAO and rainfall indicated the most significant relationship for 1 year, 1–3 years and 3–5 years approximately from the early 1980s corresponding to the dry period. However, the SOI affects rainfall only locally and with significant values more or less localised in the time-frequency space between MO, WeMO and rainfall, but this influence could be significant for low-frequency events. CWMRA shows that the components of 5–10 years and higher than 10 years are the most effective to represent climate index-rainfall significant relationships, where change in Daubechies wavelet properties can improve the correlation across the scales. Furthermore, has indicated that the short-term processes dominate the relationship index-rainfall, which masks the long-term phenomena whose influence can sometimes be very distant. As such, the rainfall variability of the study area has shown fairly significant links, at least locally with large-scale atmospheric circulation phenomena. 相似文献
14.
The discovery of decadal variability of North Atlantic Oscillation (NAO) and the introduction of Arctic oscillation (AO) concept have initiated a series of paleo-AO/NAO related studies since the mid-to-late 1990s. The progress and new findings of paleo-AO/NAO works after that time were comprehensively reviewed. The new results from the observations and modelings at four key timescales were summarized in detail: ①the reconstructions of the AO/NAO annual index over the past millennium; ②the debate on AO/NAO’s trend since early Holocene; ③the weakening of AO/NAO’s amplitude during the Last Glacial Maximum; and ④the anomalous positive phase of AO/NAO during the Last Interglacial. In addition, the possible mechanism for different timescales of AO/NAO is also summarized. Furthermore, the distinction between AO/NAO’ was mean state and amplitude, which were not explicitly separated in previous studies, were comprehensively discussed. Considering the current uncertainties related to paleo-AO/NAO studies, we encourage the community to search for more proxies having longer-than-10,000-year length with annual resolution around AO/NAO highly correlated regions. Another, we encourage long-term transient modeling on AO/NAO can be performed in order to improve our understanding of the dynamics and interaction between AO/NAO’s high-frequency variability and the climatological background, so as to further improve AO/NAO’s predictability on global warming context. 相似文献
15.
Yihui Ding Xiaolong Jia Zunya Wang Xianyan Chen Lijuan Chen 《Frontiers of Earth Science》2009,3(2):129-145
The present paper has made a comparison of major similarities and differences of extreme cold events between the cold and
warm periods for recent 50 years, in order to gain a better insight into the impact of the global warming on extreme cold
events in China. Two typical events of low temperature, ice freezing and snow disasters that occurred in January 2008 and
in the winter of 1954/1955, respectively, are selected as representative cases for the cold period (1950’s–1970’s) and the
warm period (1980’s-present). The contrasting study has revealed that these two events both occurred under long-persistent
blocking circulation over Eurasian continent, with continuous invasions of strong cold air into China mainland. They nearly
brought about similar weather disasters such as extensive low temperature, record-breaking freezing rains and exceptionally
heavy snowfalls. However, due to active northward transport of warm and moist air from Bay of Bengal and Indo-China Peninsula
in the warm period, the January 2008 case had longer freezing rain days and heavier snowstorms in South China, thus leading
to much more severe damage to electric grids and transportations. The case of the 1954/1955 winter was a stronger, extreme
cold event than the case of January 2008, in terms of magnitudes of temperature drop and severity of impact on river icing.
It was gradually recovered to normal condition while the case of January 2008 had a very rapid recovery to warming condition
due to impact of the global warming. 相似文献
16.
Until recently, research on potential economic impacts of climate change and extreme weather events on transport infrastructure was scarce, but currently this area is rapidly expanding. Indeed, there is a growing international interest, including the European area, regarding the impacts of extreme weather and climate change on the management of various transportation modes. This paper reviews briefly the present status regarding the knowledge of financial aspects of extreme weather impacts on transportation, using recent research findings from Europe, and proposes some new views in cost-benefit analysis, project appraisal and asset value protection for the management of transport systems under extreme weather risks. Quite often, risk management is understood as a response to truly extreme impacts, but this constitutes a misunderstanding. Some values are more extreme than others, and in the context of extreme weather, some weather phenomena are more extreme in their intensity and resulting impacts. An analysis of the level of costs and risks to societies, as a result of extreme weather, reveals that the risks in different European Union member states deviate substantially from each other. Also, the preparedness of different societies to deal with extreme weather events is quite variable. Extreme weather and climate change costs and risks represent a new type of item, which has to be dealt with in project appraisal. Although a fully established procedure does not exist, some fundamental ideas of cost-benefit analysis under extreme weather scenarios are presented in this paper, considering accident costs, time costs and infrastructure-related costs (comprising physical damages to infrastructures and increased maintenance costs). Cost-benefit analysis is usually associated with capital investments, but the original idea of cost-benefit analysis is not restricted to investment appraisal. Therefore, activities such as enhanced maintenance, minor upgrades, adoption of new designs, improved information services and others may be subject to cost-benefit analysis. Extreme weather and climate change costs and risks represent a new type of item, which apparently has to be dealt with also in project appraisal. A fully established procedure does not exist, although some basic principles have been introduced in analytical format. There is a lack of models to estimate extreme weather impacts and consequences and how to adapt to those costs. Optimising the efforts in maintenance and new design standards is even further away, but constitutes an overwhelming task. In this respect, new approaches and ways of thinking in preserving asset’s residual value, return periods, sustainability and equity and formal methods supplementing cost-benefit analysis are put forward. The paper concludes with a call for the need for more integrated management of transport systems. In particular, it is recognised that the different stages of transport system planning pose their own challenges when assessing the costs and benefits of policy measures, strategies and operational decisions. 相似文献
17.
R. Molarius V. Könönen P. Leviäkangas Zulkarnain J. Rönty A.-M. Hietajärvi K. Oiva 《Natural Hazards》2014,72(1):189-210
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. 相似文献
18.
19.
Progress in Researches on Ensemble Forecasting of Extreme Weather Based on Numerical Models 总被引：1，自引：1，他引：0
Under the background of climate change, extreme weather events (e.g., heavy rainfall, heat wave, and cold damage) in China have been occurring more frequently with an increasing trend of induced meteorological disasters. Therefore, it is of great importance to carry out research on forecasting of extreme weather. This paper systematically reviewed the primary methodology of extreme weather forecast, current status in development of ensemble weather forecasting based on numerical models and their applications to forecast of extreme weather, as well as progress in approaches for correcting ensemble probabilistic forecast. Nowadays, the forecasting of extreme weather has been generally dominated by methodology using dynamical models. That is to say, the dynamical forecasting methods based on ensemble probabilistic forecast information have become prevailing in current operational extreme weather forecast worldwide. It can be clearly found that the current major directions of research and development in this field are the application of ensemble forecasts based on numerical models to forecasting of extreme weather, and its improvement through bias correction of ensemble probabilistic forecast. Based on a relatively comprehensive review in this paper, some suggestions with respect to development of extreme weather forecast in future were further given in terms of the issues of how to propose effective approaches on improving level of identification and forecasting of extreme events. 相似文献
20.
Severe weather affecting European transport systems: the identification,classification and frequencies of events 总被引：1，自引：0，他引：1
Andrea Vajda Heikki Tuomenvirta Ilkka Juga Pertti Nurmi Pauli Jokinen Jenni Rauhala 《Natural Hazards》2014,72(1):169-188
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. 相似文献