首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 93 毫秒
1.
Winter storms are a major weather problem in the United States and their losses have been rapidly increasing. A total of 202 catastrophic winter storms involving ice storms, blizzards, and snowstorms, each causing >$5 million in damages, occurred during 1949–2003, and their losses totaled $35.2 billion (2003 dollars). Catastrophic winter storms occurred in most parts of the contiguous United States, but were concentrated in the eastern half of the nation where 88% of all storm losses occurred. They were most frequent in the Northeast climate district (95 storms), and were least frequent in the West district (14 catastrophic storms). The annual average number of storms is 3.7 with a 1-year high of nine storms, and one year had no storms. Temporal distributions of storms and their losses exhibited considerable spatial variability across the nation. For example, when storms were very frequent in the Northeast, they were infrequent elsewhere, a result of spatial differences in storm-producing weather conditions over time. The time distribution of the nation’s 202 storms during 1949–2003 had a sizable downward trend, whereas the nation’s storm losses had a major upward trend for the 55-year period. This increase over time in losses, given the decrease in storm incidences, was a result of significant temporal increases in storm sizes and storm intensities. Increases in storm intensities were small in the northern sections of the nation, but doubled across the southern two-thirds of the nation, reflecting a climatic shift in conditions producing intense winter storms.  相似文献   

2.
Increasing losses of life and property and damages to the environment due to sleet and related winter storm conditions have increased the need for long-term sleet storm data to better assess the point and regional risks of sleet and their long-term variations. The areas of greatest losses and frequency of catastrophes caused by sleet during 1971–2007 are the Northeast and Central regions of the U.S. These two regions experienced 72% of all the nation’s sleet losses. Most of the western U.S. had no damaging sleet-related events or losses. When sleet losses occurred, they tended to be in 2, 3, or 4 adjacent states. Sleet catastrophes were most common in January with 15 of the 30 events. The earliest storm occurred in October and the latest in March. The temporal distributions of catastrophes and their losses during 1971–2007 were similar. Both showed a secondary peak in 1976–1979, a low in 1988–1991, and then high values during the 1996–2007 period. The temporal distributions of damaging storms and losses indicate an upward trend over time.  相似文献   

3.
During 1990–1996 the United States experienced record-setting insured property losses due to numerous weather catastrophes, each event causing $100 million or more in losses (1991 dollars). The total loss in this 7-year period, after adjustment to inflation and other factors, was $39.65 billion with $15 billion coming from one event, Hurricane Andrew. In the 1990s, 72 catastrophes occurred, half of the total number in the 40 preceding years, 1950–1989. Although the total loss and the number of catastrophes were exceptionally high in the 1990s, the average loss per event was $551 million, only slightly more than the $467 million average for catastrophes during 1950–1989. Furthermore, storm intensities in the 1990s were slightly less than those during the preceding 40 years, revealing the excess losses of the 1990s to be a result of an extremely large number of damaging storms causing losses exceeding $100 million. Examination of historical values of most weather extremes including hurricanes, floods, and tornadoes, did not show an increase during the 1990s, revealing that weather changes were not the principal cause of more catastrophes. Examination of recent demographic shifts in the U.S. reveals two changes, each based on major re-locations to higher-valued property concentrated in areas either with a high frequency of damaging storms (Gulf and East Coast), or to where even a small but intense storm can cause huge losses (urban areas and West Coast). These shifts, plus the continuing growth of population in other storm-prone areas have greatly increased society's vulnerability to storm damage. An in-depth analysis of many conditions was required to establish that the high losses and numerous catastrophes of the 1990s were largely the result of societal changes and not major weather changes. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

4.
Records of very damaging snowstorms, those causing more than $25 million in property losses, across the United States were assessed to define the spatial and temporal dimensions of the nation’s snowstorm activity during 1949–2000. In this 52-year period 155 snowstorms occurred and caused losses totaling $21.6 billion (2000 dollars). The northeastern U.S. had the nation’s maximum storm occurrences (79 storms), total losses ($7.3 billion), and storm intensity. Two-thirds of all U.S. losses occurred in the Northeast, Southeast, and Central climate regions, and storm occurrences and losses were least in the western U.S. The incidence of storms peaked in the 1976–1985 period and exhibited no up or down trend during 1949–2000. However, national losses had a significant upward time trend, as did storm sizes and intensity. States with the greatest number of storms were New York (62) and Pennsylvania (58) with only 2 storms in Montana, Idaho, and Utah. Storm losses in the northeastern and southeastern U.S. had U-shaped time distributions with flat time trends for 1949–2000, but losses in the western regions and Deep South had distinct upward trends in losses and storm size. More than 90% of all storm losses in the western U.S. occurred after 1980. These findings indicating increased losses over time reflect that a rapidly growing population and vulnerability of more property at risk have been major factors affecting losses, and the lack of a change over time in snowstorm incidences suggests no change in climate during 1949–2000.  相似文献   

5.
Property insurance data available for 1949–2006 were assessed to get definitive measures of hurricane losses in the U.S. Catastrophes, events causing >$1 million in losses, were most frequent in the Southeast and South climate regions. Losses in these two regions totaled $127 billion, 85% of the nation’s total losses. During the period 1949–2006 there were 79 hurricane catastrophes, causing $150.6 billion in losses and averaging $2.6 billion per year. All aspects of these hurricanes showed increases in post-1990 years. Sizes of loss areas averaged one state in 1949–1967, but grew to 3 states during 1990–2006. Seven of the ten most damaging hurricanes came in 2004 (4) and 2005 (3). The number of hurricanes also peaked during 1984–2006, increasing from an annual average of 1.2 during 1949–1983 to 2.1 per year. Losses were $49.3 billion in 1991–2006, 32% of the 58-year total. Various reasons have been offered for such recent increases in hurricane losses including more hurricanes, more intense tropical storms, increased societal vulnerability in storm-prone areas, and a change in climate due to global warming, although this is debatable.  相似文献   

6.
The speeds of historical cool-season extratropical cyclones along the U.S. east coast, hereafter East Coast Winter Storms (ECWS), occurring during the period from 1951 to 2006 were computed. Average storm speed was 13.8 ms−1 with stronger storms generally moving faster than weaker storms and faster storms forming during the midwinter months (December–March). There was no clear trend in ECWS speed during the time period, although considerable season-to-season variability was present. The monthly and seasonal variations in storm speed could not be attributed to the El Ni?o-Southern Oscillation or North Atlantic Oscillation (NAO) alone. However, the speed of ECWS was considerably slower when both El Ni?o and the negative phase of NAO occurred simultaneously. Characteristic patterns in the upper levels of the atmosphere, specifically 300 hPa zonal winds and 500 hPa geopotential heights, were present during periods when ECWS speeds were among the slowest (and separately fastest). For slow storm speed, these patterns also prevailed during months in which El Ni?o and negative NAO phase occurred. These patterns were also present during months with extended runs of high oceanic storm surge. This provides a qualitative link between the atmospheric conditions associated with slow storms and potentially high coastal storm surge impacts. Among the prime consequences of ECWS speed are extended periods of high storm surge, mainly due to slow-moving storms. The sustained high tidal levels often lead to substantial damage caused by coastal flooding, overwash, and beach erosion.  相似文献   

7.
A unique historical data set describing the 142 storms each producing losses in excess of $100 million in the United States during the 1950–89 period were analyzed to describe their temporal characteristics. The storms caused $66.2 billion in losses (in 1991 values), 76% of the nation's insured storm losses in this period. These extreme storm catastrophes (SCs) were most prevalent in the south, southeast, northeast, and central U.S., with few in and west of the Rocky Mountains. Storm incidences were high in the 1950s, low in the 1960s-early 1970s, and increased in the 1980s. Losses due to SCs peaked in the 1950s, again in the late 1960s, with a lesser peak after 1985. The areal extent of storm losses peaked after 1975 and was least in the 1960s. The temporal variations of the three storm measures (incidence, losses, and extent) did not agree except when they all peaked in the 1950s. Regionally-derived time distributions of SCs showed a marked north-south differences in the United States with a U-shaped 40-year distribution in the northern half of the nation, and a relatively flat trend until a peak in the 1980s in the southern regions. The temporal distributions of hurricane-caused catastrophes differed regionally with occurrences in the prime areas, the southern, southeastern, and northeastern U.S., each quite different. Temporal distributions of thunderstorm and winter storm catastrophes were regionally more uniform.  相似文献   

8.
In this paper a methodology for a multi-risk assessment of an urban area is introduced and performed for the city of Cologne, Germany, considering the natural hazards windstorm, flooding and earthquake. Moreover, sources of the uncertainty in the analysis and future needs for research are identified. For each peril the following analyses were undertaken: hazard assessment, vulnerability assessment and estimation of losses. To compare the three hazard types on a consistent basis, a common economic assessment of exposed assets was developed. This was used to calculate direct economic losses to buildings and their contents. The perils were compared by risk curves showing the exceedence probability of the estimated losses. In Cologne, most of the losses that occur frequently are due to floods and windstorms. For lower return periods (10–200 years) the risk is dominated by floods. For return periods of more than 200 years the highest damage is caused by earthquakes.  相似文献   

9.
An examination of rip current fatalities in the United States   总被引：1，自引：1，他引：0  
This study analyzes fatalities caused by rip currents in the conterminous United States for the period 1994–2007. Results include the frequency of fatalities from rip currents, their cause, and their unique spatial distributions. An analysis of historical hazard event data illustrate that, on average, 35 people reportedly die from rip currents each year in the United States. Also, similar to other hazard events where unique differences in gender vulnerability have been found, men are over six times more likely to fall victim to a deadly rip current than females. Rip current fatalities are most common in the southeastern United States, with a nonuniform spatial distribution along other Atlantic, Pacific, and Great Lakes coastlines. Physical vulnerabilities are suggested as the primary cause for the unique fatality distribution found. Temporally, summer season weekends are shown to have the more fatalities than any other time of the year. A classification scheme was developed to categorize synoptic-scale weather conditions present during deadly rip current events. More than 70% of all rip current fatalities are associated with onshore winds. Specifically, a rip current fatality is most likely when a surface high pressure system creates these onshore winds. The quality of the fatality reporting database available for researchers is also assessed.  相似文献   

10.
Storms of high-intensity rainfall, including hurricanes, occur about once every 3 years in small areas of the mountains of the eastern United States posing a high debris-flow hazard. Reported casualties and monetary losses are often an insufficient and inadequate means for comparing the impact from debris flows. A simple GIS technique was used to characterize the distribution and density of debris flows for making a preliminary assessment of risk of impact on roads. This technique was used for comparison of three major severe storms resulting in numerous debris flows: August 10–17, 1940, near Deep Gap, North Carolina; August 19–20, 1969, in Nelson County, Virginia; and June 27, 1995, in Madison County, Virginia. Based on the criteria of the number of debris flows and area covered by debris flows, the August 19–20, 1969, Nelson County, Virginia, event was the most severe of the three storms and posed the greatest risk of debris-flow impact on roads.  相似文献   

11.
An innovative methodology aimed at establishing a numerical model-based high-resolution climatology of extreme winds over Switzerland is described, that makes use of the Canadian Regional Climate Model where a new windgust parameterization has been implemented. Self-nesting procedures allow windstorms to be studied at resolution as high as 2-km. The analysis of ten major windstorms concludes that the average spatial pattern and magnitude of the simulated windspeeds are well captured, and the areas that experienced extreme winds correspond well with observations and to the location where forest damage was reported following the last two of these storms. This climatology would eventually serve to form risk assessment maps based on the exceedance of windspeed thresholds. There is, however, a need for further investigations to encompass the full range of potential extreme wind cases. The ultimate goal of this methodology is to assess the change in the behaviour of extreme winds for a climate forced by enhanced greenhouse gas concentrations, and the impact of future windstorms over the Alpine region at high resolution.  相似文献   

12.
This paper examines the effect of distance on acquisition patterns for every fifth year for the period 1955–1980. The fifteen most active merger states are shown to have a relatively constant set of interstate merger relationships once the economic cycle is removed. Finally, the effect of mergers on external control levels for the United States is provided.  相似文献   

13.
The Alxa Plateau has one of the highest frequencies of dust events in China and one of the greatest contributions to East Asian dust. We compiled climate and dust storm data for the Alxa Plateau based on observational data from ten meteorological stations from 1960 to 2005. Our analysis showed that Guaizihu and Minqin dust centers had >26 days per year with dust storms versus 7–13 days for other desert and Gobi regions on the plateau. Variations in dust storm frequency during the study period showed that dust storms increased during the 1960s (until 1972), decreased until the late 1990s, and then increased slightly until 2002. About 75.6% of dust storms occurred in March, April, May, June, and July. Between 78.2 and 88.1% of the dust storms occurred during the daytime and 28.9% of the dust storms occurred between 13:00 and 16:00. The mean durations of dust storms in the Alxa Plateau ranged from 715 to 3,462 min. The annual number of minutes of dust storms averaged >1,800 min in the western Alxa Plateau. Dust storm frequency was inversely related to duration: the longer the average duration, the lower the frequency of such storms.  相似文献   

14.
There were 407 deaths from wind-related tree failures in the United States, 1995–2007. The most common cause of the deadly fallen tree was a thunderstorm (41%), followed by nonconvective high winds (35%), tropical cyclones (14%), tornadoes (7%), and snow and ice (3%). Most (62%) of the deaths were males while the median age was 44 years. The most common location of the fatality was in a vehicle struck by the tree or a vehicle that crashed into a downed tree on the road (44%), followed by persons outdoors (38%), in mobile homes (9%), and in frame houses (9%). Persons killed by wind-related tree failures during tropical cyclones and tornadoes were more commonly at home (40%) when struck than those killed at home by thunderstorm and nonconvective high winds (13%). Seasonality of the deaths varied by weather type with deaths in thunderstorms clustered during May–August, nonconvective high winds October–April, tropical cyclones August–October, tornadoes in April and November, and snow and ice December–April. Regional patterns result from frequency of the wind events, population density, and tree cover. Suggestions are made for hazard reductions.  相似文献   

15.
The significance of this study has been to give an overall view of the use of water in the arid western United States and to evaluate the key geographical, political, and legal factors that affect the water resource development in the region. This study includes the availability of water resources; usage of water, especially for irrigation, industry, urban, and household consumption; and methods of conservation to meet the growing demands for scarce water resources. The solutions for conservation are interbasin transfers with appropriate apportionment among western states; conserving water through drip irrigation; desalination of saline water; decreasing demand through increasing efficiency; and establishing cooperation among the western states for equitable distribution of water. The western states have to realize that scarce water in the West should be used judiciously and conservation practices have to be followed strictly to meet the future need for water. In recent years, the federal government is becoming hesitant to extend large amount of money for water projects in the West because of growing federal deficits. Water may play an important role in maintaining the standard of living for the fast growing population in the sunbelt and in accelerating the pace of economic development in the western United States.A paper presented at the International Symposium on the Exploration and Utilization of Natural Resources in Arid Areas held under the auspices of the Chinese Academy Science, ISEUNRAA, Xinjiang, Urumqi, China, from August 7–13, 1985.  相似文献   

16.
 Hydrological records collected from water gauge stations since the 1950s demonstrate that the Taihu lake level is rising. The average rate of the lake-level rise is 0.4–1.1 mm/year during the non-flood season, resulting directly from a rise in sea level. High rates of 3.0–5.0 mm/year of rise are even recorded during the wet season. This indicates increasing human activities such as reclamation, sluicing and embanking, which significantly hinder the expulsion of extra lake water to the coast shortly after a rainfall. Generally, the lake level of the western inlet is higher than that of the eastern outlet. However, the lake-level difference between the west and east has been diminished annually from ∼10–15 cm in the 1950s to <3 cm at the present time. During non-flood seasons, the lake-level difference even appears to be reversed, indicating a retrogression of the lake flow from east to west. It is predicted that the Taihu drainage basin will lose much of its natural water-expelling ability in the next 50 years as the sea level continues to rise, and retrogression will likely occur during the flood season in the near future. Received: 13 March 1998 · Accepted: 21 July 1998  相似文献   

17.
Death tolls from tornadoes in Bangladesh are the highest in the world due to lack of storm warnings, poor communication, weak housing, and lack of shelters from strong winds in tornadoes and nor’westers. Based on surveys of housing types and designs in the Tangail district, a household tornado shelter is proposed to be placed in the elevated storage platform that is common in houses. The shelter is 2 m tall, 1.2 m wide, and 2–4 m long (4.8–9.6 m3 in volume) with the floor of the shelter placed one meter below the floor of the house. Walls are 7–10 cm thick and made of concrete or an earthen wall stabilized with cement or strengthened with bamboo or bricks. A survey of 200 residents of the region found nearly universal acceptance for the shelter design, and residents were eager for installation of the household shelters. The shelter cost is 2,500–10,000 taka (US50 to50 to 200) depending on local material and labor costs but residents were willing to pay an average of only 1,071 taka (US$21) toward the cost of the shelter. Families with greater income and land holdings and families in villages with recent tornado experience were willing to spend more for a shelter. A pilot project to install household tornado shelters in selected villages and monitor their use, along with continued efforts to issue storm warnings, communicate the warnings, and improve education about storm hazards, will prevent injuries and save lives in Bangladesh and reduce the descent into poverty that results from losses in severe local storms.  相似文献   

18.
A database was compiled for the period 1977–2007 to assess the threat to life in the conterminous United States from nontornadic convective wind events. This study reveals the number of fatalities from these wind storms, their causes, and their unique spatial distributions. Nontornadic convective wind fatalities occur most frequently outdoors, in vehicles including aircraft, or while boating. Fatalities are most common in the Great Lakes and Northeast, with fewer fatalities observed in the central United States despite the climatological peak in severe thunderstorms in this region. Differences in fatality locations between tornadoes and nontornadic convective wind events highlight the unique combination of physical and social vulnerabilities involved in these deaths. Understanding these vulnerabilities is important to future reduction of nontornadic convective wind fatalities.  相似文献   

19.
Mantle derived xenoliths in India are known to occur in the Proterozoic ultrapotassic rocks like kimberlites from Dharwar and Bastar craton and Mesozoic alkali igneous rocks like lamrophyres, nephelinites and basanites. The xenoliths in kimberlites are represented by garnet harzburgites, lherzolites, wehrlite, olivine clinopyroxenites and kyaniteeclogite varieties. The PT conditions estimated for xenoliths from the Dharwar craton suggest that the lithosphere was at least 185 km thick during the Mid-Proterozoic period. The ultrabasic and eclogite xenoliths have been derived from depths of 100–180 km and 75–150 km respectively. The Kalyandurg and Brahmanpalle clusters have sampled the typical Archaean subcontinental lithospheric mantle (SCLM) with a low geotherm (35 mW/m2) and harzburgitic to lherzolitic rocks with median Xmg olivine > 0.93. The base of the depleted lithosphere at 185–195 km depth is marked by a 10–15 km layer of strongly metasomatised peridotites (Xmg olivine > ∼0.88). The Anampalle and Wajrakarur clusters 60 km to the NW show a distinctly different SCLM; it has a higher geotherm (37.5 to 40 mW/m2) and contains few subcalcic harzburgites, and has a median Xmg olivine = 0.925. In contrast, the kimberlites of the Uravakonda and WK-7 clusters sampled quite fertile (median Xmg olivine ∼0.915) SCLM with an elevated geotherm (> 40 mW/m2). The lamrophyres, basanites and melanephelinites associated with the Deccan Volcanic Province entrain both ultramafic and mafic xenoliths. The ultramafic group is represented by (i) spinel lherzolites, harzburgites, and (ii) pyroxenites. Single pyroxene granulite and two pyroxene granulites constitutes the mafic group. Temperature estimates for the West Coast xenoliths indicate equilibration temperatures of 500–900°C while the pressure estimates vary between 6–11 kbar corresponding to depths of 20–35 km. This elevated geotherm implies that the region is characterized by abnormally high heat flow, which is also supported by the presence of linear array of hot springs along the West Coast. Spinel peridotite xenoliths entrained in the basanites and melanephelinites from the Kutch show low equilibrium temperatures (884–972°C). The estimated pressures obtained on the basis of the absence of both plagioclase and garnet in the xenoliths and by referring the temperatures to the West Coast geotherm is ∼ 15 kbar (40–45 km depth). The minimum heat flow of 60 to 70 mW/m2 has been computed for the Kutch xenolith (Bhujia hill), which is closely comparable to the oceanic geotherm. Xenolith studies from the West Coast and Kutch indicate that the SCLM beneath is strongly metasomatised although the style of metasomatism is different from that below the Dharwar Craton.  相似文献   

20.
A total of 269 tropical storms and hurricanes originated in the North Atlantic basin from 1960–1989. Of these, 76 made landfall on the continental United states. This study divides the 76 tropical storms into their month of formation. Seasonal shifts in the principal areas of tropical cyclone formation over the Atlantic basin have been recognized for many decades. The results of the study suggest that the early and late season tropical cyclones develop in areas which are first affected by the position of the sun, resulting in an increase in water temperatures. These cyclones normally make landfall along the Gulf Coast and usually are of low intensity. Formation areas shift eastward in mid-summer with a slight increase in intensity. By late August and early September, the formation areas have extended to the Cape Verde Islands. These storms tend to strike the east coast of the US and are normally more intense. By the end of the hurricane season, the primary formation area has shifted back to the Gulf of Mexico, with low intensity storms affecting the Gulf Coast.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号