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David Changnon and Stanley A. Changnon

Abstract

Uses of climate information have grown considerably in the past 15 years as a wide variety of weather-sensitive businesses sought to deal effectively with their financial losses and manage risks associated with various weather and climate conditions. Availability of both long-term quality climate data and new technologies has facilitated development of climate-related products by private-sector atmospheric scientists and decision makers. Weather derivatives, now widely used in the energy sector, allow companies to select a financially critical seasonal weather threshold, and, for a price paid to a provider, to obtain financial reparation if this threshold is exceeded. Another new product primarily used by the insurance industry is weather-risk models, which define the potential risks of severe-weather losses across a region where few historical insured loss data exist. Firms develop weather-risk models based on historical storm information combined with a target region’s societal, economic, and physical conditions. Examples of the derivatives and weather-risk models and their uses are presented. Atmospheric scientists who want to participate in the development and use of these new risk-management products will need to broaden their educational experience and develop knowledge and skills in fields such as finance, geography, economics, statistics, and information technology.

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Stanley A. Changnon and David Changnon

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Hail-day occurrences during a 100-yr period, 1896–1995, derived from carefully screened records of 66 first-order stations distributed across the United States, were assessed for temporal fluctuations and trends. Shorter-term (5- and 10-yr) fluctuations varied greatly and were often dissimilar between adjacent stations reflecting localized differences in hailstorm activity, making temporal interpretations difficult. But temporal fluctuations based on 20-yr and longer periods exhibited regional coherence reflecting the control of large-scale synoptic hail-producing systems on the point distributions over broader areas. Classification of station fluctuations based on 20-yr periods revealed five types of distributions existed across most of the nation. One present in the Midwest had a peak in hail activity in 1916–35 followed by a general decline to 1976–95. Another distribution had a midcentury peak and was found at stations in three areas: the central high plains, northern Rockies, and East Coast. The third distribution peaked during 1956–75 and was found at stations in the northern and south-central high plains. The fourth temporal distribution showed a steady increase during the 100-yr period, peaking in 1976–95, and was found in an area from the Pacific Northwest to the central Rockies and southern plains. The fifth distribution found at stations in the eastern Gulf Coast had a maximum at the beginning of the century and declined thereafter. The 100-yr linear trends defined four regions across the United States with significant up trends in the high plains, central Rockies, and southeast, but with decreasing trends elsewhere in the nation. These up trends have occurred in areas where hail damage is greatest, and the trends matched well with those defined by crop-hail insurance losses and those found in studies of thunderstorm trends. The national average based on all station hail values formed a bell-shaped 100-yr distribution with hail occurrences peaking in midcentury. Thunderstorm data from the 66 stations, also based on screening to ensure quality data, revealed a bell-shaped distribution similar to the hail-day distribution, and national hail insurance loss values have declined since the 1950s, also agreeing with the hail-day decrease since midcentury. The national distribution differs markedly from certain regional distributions illustrating the importance of using regional analysis to assess temporal fluctuations in severe weather conditions.

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David Changnon and Stanley A. Changnon

Abstract

Crop-hail insurance loss data for 1948–94 are useful as measures of the historical variability of damaging hail in those 26 states where most crop damages occur. However, longer records are needed for various scientific and business applications, as well as information on potential losses in United States’ areas without crop insurance. The long-term (1901 to present) data on hail-day incidences, as derived from National Weather Service historical station records, were investigated to determine if some form of a hail-day expression related well to the insurance losses. The areal extent of insured areas of Illinois, Texas, and Nebraska experiencing growing season frequencies of hail days matching or exceeding the once in 10-yr frequencies was found to have the best relationship with insured loss values. The computed correlation coefficients were +0.97 for Illinois, +0.73 for Texas, and +0.91 for Nebraska. These values appear to be a useful surrogate for 1) estimating pre-1948 loss values, 2) estimating loss values in areas with no insurance, and 3) further research involving other states with different crop and hail conditions.

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Stanley A. Changnon Jr.

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Stanley A. Changnon Jr.

Abstract

Average durations of thunder events are greatest (>120 min) in the Oklahoma–Kansas area and least (<60 min) along the west coast and northeast. The average point duration of thunder activity ranges from 10 000 to 12 000 min along the Gulf Coast, 8000 to 10 000 min in the Midwest, exceed 6000 min in Arizona, but is only 1000 to 2000 min in the northeast, and 500 to 1000 min along the west coast. Nocturnal thunder events typically last 10 to 30 min longer than those in the daytime in all areas except for the western mountains and extreme southeast where daytime events exceed those at night by 5 to 15 min, on the average.

The trends in thunder event activity during the 1948–77 period indicate four distinctly different characteristics. The stations in the southwestern and northwestern United States exhibit flat, unchanging trends in events during the 30 years, but events in the northern Great Plains-Midwest gradually decreased with time; those in the Great Lakes increased since 1950; and those in the southeastern United States decreased to minimums in the 1960s and then increased to 1977. The temporal distribution of extratropical cyclonic activity in July explains 25% to 50% of the temporal variations in July thunder events over most of the central and eastern United States. However, increases in thunder events since the late 1960s in the Upper Midwest and along the East Coast were not associated with increased cyclonic activity.

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Stanley A. Changnon Jr.

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No abstract available.

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Stanley A. Changnon Jr.

Abstract

The temporal histories of 702 convective echoes measured in the St. Louis area during the 1973 summer were studied to discern potential effects on echo behavior of the urban influences and those effects resulting from the merger of two or more echoes. The 190 echoes that merged grew faster (50%), became taller (52%), and lasted longer (122%) than non-merger echoes. The average echo top growth 10 min after a merger was 1500 m, and on any given day 80% of the heights of merger echoes at a given stage of echo life were higher than those of non-merger echoes. The 137 echoes that crossed the urban area were longer lasting (119%), faster growing (61%), taller (30%), and more merged (44% vs 23%) than the non-urban echoes. The 61 urban echoes that subsequently merged over or beyond St. Louis were demonstrably longer lasting (110 vs 44 min) and taller (4800 m at 10 min after entry into the urban area and 5900 m at urban exit) than 76 urban echoes that did not merge. The urban echo that merged was also measurably different than the rural merged echo. The average urban merged echo lasted 51% longer, grew 100% faster, and achieved a height 20 min after merger that was 133% higher. The urban area apparently affected nearly half (44%) of the echoes over it leading to larger, more vigorous, and longer lasting storms that always merged with one or more other storms. This dynamic process leads to more rain, short-duration rainstorms and hailstorms in and east of St. Louis.

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Stanley A. Changnon

Thunderstorm rainfall amounts during the 1950–94 period were determined for 51 first-order stations distributed across the United States, and these values were assessed for seasonal and annual variations in both space and time. Thunderstorms produce 48% of the average annual precipitation received in the Mississippi River basin, which embraces 41% of the United States. Hence, the temporal and spatial variations in thunderstorm rainfall are major factors affecting most of the nation's water cycle. However, thunderstorm rainfall is only a small part of the total precipitation on the West Coast, typically less than 10% of the annual total. Thunderstorms maximize in the summer in most areas and produce 72% of the total summer rainfall that occurs east of the Rocky Mountains. Thunderstorm rainfall in the spring exceeds summer values in the southern plains and portions of California with 40% of the annual average storm precipitation, but spring values rank second in most areas of the nation. Thunderstorm rainfall amounts explain at least 50% of the variation found in annual total precipitation across large portions of the nation. Thunderstorm rainfall departures below average in the driest five years were found to closely match those of total precipitation deficiencies at all stations, revealing that the absence of storm rainfall is a major factor in droughts. Similarly, the magnitude of thunderstorm rainfall departures in the five wettest years of 1950–94 matched the magnitude of the total precipitation departures, revealing that thunderstorms have a sizable influence in producing extremely wet as well as dry years across the nation. The temporal distribution of thunderstorm rainfall during 1950–94 showed 10%–55% increases over time in most parts of the nation except the upper Midwest and a small portion of the Southeast. Increases were statistically significant in the northern high plains and intermountain area of the West. Trends of storm days with heavy rainfall were also upward across the entire nation, being sizable on the West Coast, Intermountain West area, and Northeast. The national pattern based on temporal shifts in thunderstorm rainfall is in agreement with that based on shifts in storm frequencies indicating that the temporal increases in storm rainfall were a result of more thunderstorms over time and more storm days with heavy rainfall.

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Stanley A. Changnon

Events in 1988 helped focus the attention of several states on the global climate change issue. Consequently, the National Governors' Association conducted an assessment in 1989 and recommended various actions. By 1994, 22 states have enacted laws or regulations and/or established research programs addressing climate change. Most of these “no regrets” actions are set up to conserve energy or improve energy efficiency and also to reduce greenhouse gas emissions. Illinois has adopted an even broader program by 1) establishing a Global Climate Change Office to foster research and provide information and 2) forming a task force to address a wide array of issues including state input to federal policies such as the Clinton administration's 1993 Climate Change Action Plan and to the research dimensions of the U.S. Global Climate Change Research Program. The Illinois program calls for increased attention to studies of regional impacts, including integrated assessments, and to research addressing means to adapt to future climate change. These various state efforts to date help show the direction of policy development and should be useful to those grappling with these issues.

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Stanley A. Changnon Jr.

Abstract

Collection of crop loss assessment values adjacent to halipads has allowed a comparative investigation to determine which hailfall characteristics were related to the degree of loss to wheat, corn and soybean crops in Illinois. Establishment of such relationships is important information because it indicates which characteristics must be measured, either with hailpads or other hail-sensing devices, to provide meaningful evaluations of hail suppression project results and useful data for crop-hail studies. Because of factors related to the thickness of wheat stands, wheat losses were found to be closely related to the frequency of hailstones with diameters >0.25 inch. Corn and soybean losses exhibited varying seasonal relationships with either hailstone frequency and/or hailfall energy values. Corn losses in May related only to stone frequency, whereas corn losses in later growth stages (July-August) related well to both stone frequency and energy. A given number of hailstones falling in May produced considerably less corn damage than the same number in the June-August period. Soybean losses also related to both energy and stone frequency, although marked seasonal variations existed with each characteristic. An energy value of 1.0 ft-lb ft−2 produced, on the average, soybean loss of 12% in May, 15% in July-August, and 61% in June. Derived relationships indicated that 100 hailstones ft−2 (each >0.25 inch diameter) produced a 42% soybean loss in June, but only a 13% loss in July-August. The high correlations between crop losses and hailstone frequency and/or energy values indicate that potential crop losses in uncropped areas can be estimated from hail-sensing devices that measure both hail characteristics.

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