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- Author or Editor: Stanley A. Changnon x
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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.
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.
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.
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.
Abstract
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.
Abstract
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.
Abstract
Cooperative substation records of hail and thunder incidences have been used as a source of data to develop more accurate and detailed average patterns of these phenomena. Since the accuracy and completeness of records by volunteer observers are generally considered questionable, a method of determining accurate substation records of thunder and hail was devised. The evaluation method relies strongly on comparisons of substation data with those from nearby first-order stations. The number of stations with accurate hail records was found to be greater than the number with accurate thunder records. Reliable records of both events in Illinois and surrounding States have provided very useful information.
Abstract
Cooperative substation records of hail and thunder incidences have been used as a source of data to develop more accurate and detailed average patterns of these phenomena. Since the accuracy and completeness of records by volunteer observers are generally considered questionable, a method of determining accurate substation records of thunder and hail was devised. The evaluation method relies strongly on comparisons of substation data with those from nearby first-order stations. The number of stations with accurate hail records was found to be greater than the number with accurate thunder records. Reliable records of both events in Illinois and surrounding States have provided very useful information.
Abstract
The average temporal and spatial distributions of thunder events (periods of discrete thunder activity heard at a point) in the conterminous United States were found to be generally similar to those of thunder days. Annual averages of thunder events peak along the Gulf Coast (>100) and are also quite high in the central United States (Kansas, Missouri, Illinois with >75 events), and in the southwest (Arizona with 60 events). Thunder events are least along the west coast (<20) and in the northeast (<30). Multiple events per day are greatest in the Midwest (Illinois, Iowa) averaging 1.7 events per summer day, and are also high in the southwest (Arizona) with 1.5 events. This causes these two maxima in thunder event activity to be more pronounced than those found on the pattern of average thunder days.
The average patterns for the thunder event frequencies, multiple events per day, and durations reveal that convective activity is weakest and shortlived along the west coast and in the northeast. The high incidence of events per day in the Midwest reflects multiple storm incidences likely related to MCCs and nocturnal storm activity. The peak in thunder event activity is present in the central United States in all months and rotates from the lower Mississippi Valley to the central Great Plains-Midwest and then back, and its position is always closely related to the major center of cold frontal activity. The thunder peak in the southwest is related to the summer monsoon intrusion of moist tropical Pacific air and related frontal activity. The summer-fall peak in thunder events along the Gulf Coast-Florida is a result of sea breeze induced convergence, localized heating, and occasional tropical disturbances.
Abstract
The average temporal and spatial distributions of thunder events (periods of discrete thunder activity heard at a point) in the conterminous United States were found to be generally similar to those of thunder days. Annual averages of thunder events peak along the Gulf Coast (>100) and are also quite high in the central United States (Kansas, Missouri, Illinois with >75 events), and in the southwest (Arizona with 60 events). Thunder events are least along the west coast (<20) and in the northeast (<30). Multiple events per day are greatest in the Midwest (Illinois, Iowa) averaging 1.7 events per summer day, and are also high in the southwest (Arizona) with 1.5 events. This causes these two maxima in thunder event activity to be more pronounced than those found on the pattern of average thunder days.
The average patterns for the thunder event frequencies, multiple events per day, and durations reveal that convective activity is weakest and shortlived along the west coast and in the northeast. The high incidence of events per day in the Midwest reflects multiple storm incidences likely related to MCCs and nocturnal storm activity. The peak in thunder event activity is present in the central United States in all months and rotates from the lower Mississippi Valley to the central Great Plains-Midwest and then back, and its position is always closely related to the major center of cold frontal activity. The thunder peak in the southwest is related to the summer monsoon intrusion of moist tropical Pacific air and related frontal activity. The summer-fall peak in thunder events along the Gulf Coast-Florida is a result of sea breeze induced convergence, localized heating, and occasional tropical disturbances.
Abstract
A new national database for freezing-rain occurrences during the 1945–2000 period provided an opportunity for a study of the potential urban effects on freezing-rain events. Numerous past studies of snowfall events in urban areas have defined decreases of 10%–35% related to the urban heat island. The heat island, which acts to elevate near-surface temperatures, could also keep some freezing-rain situations from occurring in the city. The study involved four cities in the Midwest and Northeast for which the average annual number of days with freezing rain are three or more, for which data from in-city stations existed, and for which data for several surrounding rural stations existed. The two largest qualifying cities, New York City, New York, and Chicago, Illinois, had sizable reductions in average and maximum annual freezing-rain-day frequencies, ranging from 16% to 43% less than values of surrounding rural stations, and their freezing-rain “seasons” were 1–2 months shorter than those in surrounding rural areas. The ocean/lake influences at both cities, along with the heat island, also helped to reduce the local incidence of freezing-rain events. Two qualifying smaller urban areas, Washington, District of Columbia, and St. Louis, Missouri, had reductions in freezing-rain-day occurrences but had no shifts in the length of their freezing-rain seasons. Results suggest that freezing-rain occurrences in large cities are decreased between 10% and 30% by the heat island, which acts to keep rain from freezing to urban surfaces.
Abstract
A new national database for freezing-rain occurrences during the 1945–2000 period provided an opportunity for a study of the potential urban effects on freezing-rain events. Numerous past studies of snowfall events in urban areas have defined decreases of 10%–35% related to the urban heat island. The heat island, which acts to elevate near-surface temperatures, could also keep some freezing-rain situations from occurring in the city. The study involved four cities in the Midwest and Northeast for which the average annual number of days with freezing rain are three or more, for which data from in-city stations existed, and for which data for several surrounding rural stations existed. The two largest qualifying cities, New York City, New York, and Chicago, Illinois, had sizable reductions in average and maximum annual freezing-rain-day frequencies, ranging from 16% to 43% less than values of surrounding rural stations, and their freezing-rain “seasons” were 1–2 months shorter than those in surrounding rural areas. The ocean/lake influences at both cities, along with the heat island, also helped to reduce the local incidence of freezing-rain events. Two qualifying smaller urban areas, Washington, District of Columbia, and St. Louis, Missouri, had reductions in freezing-rain-day occurrences but had no shifts in the length of their freezing-rain seasons. Results suggest that freezing-rain occurrences in large cities are decreased between 10% and 30% by the heat island, which acts to keep rain from freezing to urban surfaces.
A paradox has developed involving on one hand sizeable reductions during the last two years in federal support of weather modification, as opposed to major scientific-technical advances in the field plus strong recommendations for increased federal support from the scientific community. The major recent advances include the capability to operationally dissipate cold fogs, to enhance snow from orographic clouds, and to increase rain from tropical clouds, plus the discovery of sizeable urban-related increases in rainfall. Other advances include special weather radars, aircraft with new cloud sensors and the capability to penetrate thunderstorms, new seeding materials and delivery systems, and new techniques for evaluation of projects. These have been coupled with the spread of weather modification around the world and with the initiation of major seeding projects in Colorado (NHRE, HIPLEX, and San Juan Project), Florida, South Dakota, and Illinois-Missouri (METROMEX). Several groups (NACOA, NAS, ICAS, NWC, AMS) all made a series of positive recommendations for advancing the field through more federal support and reorganization. Yet, beginning in FY74, federal support for weather modification dropped 21% when other R&D increased 11%. Many possible causes for the paradox appear, including fear of weather changes, lack of scientific commitment, and a series of public, scientific, political, and military controversies. The three basic issues are that weather modification is still an immature technology; the socio-economic impacts are ill defined; and its management has been uncertain. Proper resolution of the paradox is more apt to occur either because of a dramatic scientific breakthrough or from growing concerns about weather and climate-related environmental changes.
A paradox has developed involving on one hand sizeable reductions during the last two years in federal support of weather modification, as opposed to major scientific-technical advances in the field plus strong recommendations for increased federal support from the scientific community. The major recent advances include the capability to operationally dissipate cold fogs, to enhance snow from orographic clouds, and to increase rain from tropical clouds, plus the discovery of sizeable urban-related increases in rainfall. Other advances include special weather radars, aircraft with new cloud sensors and the capability to penetrate thunderstorms, new seeding materials and delivery systems, and new techniques for evaluation of projects. These have been coupled with the spread of weather modification around the world and with the initiation of major seeding projects in Colorado (NHRE, HIPLEX, and San Juan Project), Florida, South Dakota, and Illinois-Missouri (METROMEX). Several groups (NACOA, NAS, ICAS, NWC, AMS) all made a series of positive recommendations for advancing the field through more federal support and reorganization. Yet, beginning in FY74, federal support for weather modification dropped 21% when other R&D increased 11%. Many possible causes for the paradox appear, including fear of weather changes, lack of scientific commitment, and a series of public, scientific, political, and military controversies. The three basic issues are that weather modification is still an immature technology; the socio-economic impacts are ill defined; and its management has been uncertain. Proper resolution of the paradox is more apt to occur either because of a dramatic scientific breakthrough or from growing concerns about weather and climate-related environmental changes.
