Showing papers by "Stanley A. Changnon published in 2003"

Shifting Economic Impacts from Weather Extremes in the United States: A Result of Societal Changes, Not Global Warming

Abstract: Loss values from extremes in the U.S. and elsewhere have been more qualitativethan quantitative, but recent pressures for better information have led to newassessments and better estimates of financial losses from extremes. These pressureshave included concerns over potential impacts of more extremes due to global warmingfostered by ever increasing costs to the insurance industry and government from weather extremes; plus a series of massive losses during the past 15 years (drought of 1988–1989,Hurricane Andrew in 1992, and Midwestern 1993 floods). These recent assessmentsattempted to adjust data for societal changes over time and thus derived new and betterestimates of losses for seven major extremes than existed previously. Three extremeshave annual average losses in excess of a billion dollars (1998 dollars) includinghurricanes ($4.2 billion), floods ($3.2 billion), and severe local storms ($1.6 billion).One extreme and its adjusted losses exhibit upward trends (floods), but all others showno increases with time or temporal decreases (hail, hurricanes, tornadoes, and severethunderstorms). Annual national losses during 1950–1997 from the three major extremes, plus four others (hail, tornadoes, winter storms, and wind storms), collectively reveal no upward or downward trend over time, with an average annual loss of $10.3 billion. The quality loss values do not indicate an increase as has been postulated for global warming. The good news is that better estimates of impacts now exist, but the bad news is that they are still estimates and do not include sizable unmeasured losses. If accurate data on the economic impacts from weather extremes are seen as important for scientific research and policy-making for global warming, the U.S. needs a continuing program to adequately measure losses from weather extremes.

Characteristics of Ice Storms in the United States

Abstract: Freezing rainstorms in the United States during 1949–2000 resulted in 87 catastrophic events, storms causing property losses of more than $1 million, with resulting losses totaling $16.3 billion. Catastrophes and their losses were greatest in the northeast, southeast, and central United States, and only 3% occurred in the western United States. A greater percentage of the freezing-rain occurrences in the deep South produced catastrophes than did freezing-rain occurrences in the northern United States, a result of differences in storm-producing conditions. A dense network of observers who measured ice storms during a 9-yr period provided definitive data on damaging storm areas and ice thicknesses on wires. The geographic distribution of the 368 damaging–ice storm areas matched well with that of catastrophes; both were greatest in a belt from the Southwest, across the Midwest, and into New England. Storm-area sizes ranged from 205 to 796 000 km2, with 50% being less than 21 840 km2. Most storm-area...

Temporal and Spatial Variations of Freezing Rain in the Contiguous United States: 1948–2000

Abstract: A new freezing-rain-days database was used to define the spatial and temporal distributions of freezing-rain days across the contiguous United States. The database contained 988 stations, spanning the period 1948–2000. Areas averaging one or more days of freezing rain annually included most of the eastern half of the United States and the Pacific Northwest. The national maximum is in portions of New York and Pennsylvania, a result of several weather conditions conducive to freezing rain. Other maxima included an east–west zone across the Midwest, an area along the eastern Appalachians, and the Pacific Northwest. The latter two maxima have high frequencies as a result of the mountains, which trap low-level cold air with warm air moving above, resulting in freezing rain. National maximum annual values during 1948–2000 were 3–5 times as great as annual averages, but the two patterns were similar. Average patterns for three discrete 17-yr periods between 1948 and 2000 were very similar, but the magni...

Urban Modification of Freezing-Rain Events

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 surroun...

The Tristate Hailstorm: The Most Costly on Record

Abstract: The most damaging hailstorm ever recorded moved from eastern Kansas to southern Illinois during an 8-h period on 10 April 2001, depositing 2.5- to 7.5-cm-diameter hailstones along a 585-km path. A classic long-lived supercell storm was the cause of the record hailfalls. The record-large hailswath size, large and often windblown hailstones, and movement over portions of the St. Louis and Kansas City urban areas led to $1.5 billion in insured losses. This tristate hailstorm and other adjacent hailstorms collectively created $1.9 billion in insured losses in a 2-day period, becoming the ninth most costly weather catastrophe in the United States since property insurance records began in 1949.

Sources of Data on Freezing Rain and Resulting Damages

Abstract: Freezing rain produces major damages each year in the United States, and various affected groups continue to seek data on the incidence and losses produced by freezing rain. The various kinds of data available about freezing rain and related damages have been identified and assessed as part of a project to develop long-term databases. Data include long-term records of the occurrences of freezing rain, 50-yr records of insured property losses, and measures and estimates of ice loading on wires and structures. Many years of interactions with affected and interested groups and individuals, such as the insurance industry and design engineers, led to the preparation of this summary that describes the various sources of data on freezing-rain and ice-storm damages. The benefits and limitations of each form of data are presented to help to guide potential data users.

Problems in estimating impacts of future climate change on midwestern corn yields

Abstract: Recent studies of trends in Midwestern precipitation show marked increases over the last 50 years of the 20th Century, and most climate models project that future rainfall in the Corn Belt will be increased further. During five years, 1988–1991 and 1994, field tests were conducted on agricultural test plots in central Illinois, an area typical of the Corn Belt, to discern how corn yields reacted to varying levels of added rainfall (+10%, +25%, and +40%) during the growing season. The best treatment over the five years was a 40% rain increase, with an average yield increase of 9%. Its yield increase was up to 34% in a hot-dry year, but below that of natural rainfall in a wet year as were the yields of the other lesser increases. The average yield changes from the three treatments were not statistically significantly different. Major interannual yield differences were found in the yields for each rain treatment, reflecting how rain timing and temperatures also have major effects on yields. A 40% summer rain increase has little influence if natural rains do not occur in the high stress period of mid summer. The plots results show that only small average increases in corn yields occur from growing season rain additions in the 10% to 40% range, except in dry years. Weather-crop yield regression models incorporating the same rain increases predict greater yield increases than found in these field tests. This suggests that future yields projected for a wetter climate using yield-weather models may be over-estimated. The plot sample size is small but conditions sampled in the five years represented 43% of all past 97 growing seasons in central Illinois and extremely good and bad weather years, which resulted in large between-year yield differences. Hence, the experimental results provide useful information about how increased rainfall may affect future corn yields, especially since the sample included three of the five types of dry growing seasons found in the area's climate since 1900.

Impact of Spring 2000 Drought Forecasts on Midwestern Water Management

Abstract: In March 2000, the National Oceanic and Atmospheric Administration issued forecasts of spring and summer droughts for five Midwestern states. Summer brought heavy rains across the Midwest, ending the drought and revealing the forecast’s failure. The uses of forecasts and the resulting impacts were assessed by interviewing 45 state agency water managers in the drought region plus managers of 31 community water systems facing serious shortages. All state water managers had received the forecasts and most believed the forecast was accurate. As a result of the forecast, 70% of them initiated various activities, primarily by warning managers of water short communities and initiating meetings of state drought response groups. Many managers of water-short local systems reported that the forecast led them to impose water use restrictions or to seek new sources of water. Most state water officials and local managers felt the forecast-based actions were beneficial and created few problems. State climatologists hand...

Climate-years in the true prairie : Temporal fluctuations of ecologically critical climate conditions

Abstract: The True Prairie (TP) is a large area in the central U.S. which was a tall grass prairie for thousands of years prior to its conversion to crop land. An analysis of climatically controlling factors indicated that the tall grass prairie is favored by the ratio of warm season precipitation to potential evapotranspiration exceeding 0.75 (west boundary), cold season precipitation less than 38 cm (south boundary), high cold-season frequency of thunderstorms (north boundary), and high drought frequencies (entire region). A `climate-year' approach was used to assess the temporal and spatial variability of these conditions during the 20thcentury. This analysis did not reveal any long-term trends in most climate-year types, although there were significant decadal-scale fluctuations, most notably a high frequency of drought-type years in the 1930s and 1950s. However, the well-documented upward trend in precipitation is manifested in an increasing frequency of one climate-year type characterized by above normal cold season precipitation in the southern border area of the TP.

Quantification of Climate Conditions Important to the Tall Grass Prairie

Abstract: The geologic history of the tall grass prairie in central North America reveals the prairie began developing 10,000 years ago after the Pleistocene ice sheets had retreated into Canada. The long-lived triangular shaped prairie survived several climatic shifts during the Holocene. Scientists have studied the anomaly—grasses where many climate conditions indicate forests should have been growing—by offering a myriad of potential climate, physiographic, and human factors. By the 1960s scientists recognized that fire was the key to the prairie’s presence—fires destroyed forests but grasses survived and were generally enhanced by prairie fires. Scientists have since believed that lightning, in addition to fires set by Native Americans, were the reasons for the region’s high frequency of prairie fires. Long records of various climate conditions collected since the 1890s now allow a quantitative comparison of the prairie versus non-prairie climate conditions. Assessment of drought conditions during the 20 th Century shows that the prairie triangle experienced 50% to 200% more severe drought years than did the forested areas north and south of the prairie, an important factor behind the prairie’s presence. Cold season precipitation, averaging <34 cm, in the prairie was too low to sustain the deciduous forests that grew south and east of prairie, and resulted in a dry season necessary for frequent prairie fires. The rougher topography and numerous streams to the prairie’s south also served as firebreaks to contain fires, whereas the flat lands of the prairie with few major rivers had fewer natural firebreaks. West of the tall grass prairie was a short grass prairie, the climax vegetation in the more arid High Plains. Large differences in lightning activity exist along the prairie’s northern boundary during the prairie’s fire season (October-March), suggesting that the much lower storm incidences to the north help explain the presence of forests in that area. Long climatic records, which were not available for use in earlier studies, have allowed quantification of the climate factors that helped shape the Midwest’s tall grass prairie.

Geographical and Temporal Variations in Thunderstorms in the Contiguous United States During the 20th Century

Abstract: Annual and seasonal measures of thunderstorm-day occurrences in the contiguous United States for 1896-1995, based on data from 841 weather stations, reveal the Florida-Gulf Coast area has the maximum number of storms in all seasons with a secondary high in the central United States and a third in the southwest. Storm incidence is least along the West Coast and in the Northeast. The 100-yr. average annual storm pattern is considerably different from those in earlier studies based on fewer stations. Summer is the peak season of thunderstorm activity, although spring occurrences rank highest in the southern plains. Thunderstorms are most frequent in winter along the West Coast. The temporal distribution of thunder days during the 1896-1995 period reveals consistency with most of the nation's major areas of high and low storm incidences in each 20-yr. period. However, major temporal shifts occurred in the Great Plains and Gulf Coast. The most storm active 20-yr. period was 1936-1955, and the 1896-1915 period ...

NOTES AND CORRESPONDENCE Sources of Data on Freezing Rain and Resulting Damages

Abstract: Freezing rain produces major damages each year in the United States, and various affected groups continue to seek data on the incidence and losses produced by freezing rain. The various kinds of data available about freezing rain and related damages have been identified and assessed as part of a project to develop long-term databases. Data include long-term records of the occurrences of freezing rain, 50-yr records of insured property losses, and measures and estimates of ice loading on wires and structures. Many years of interactions with affected and interested groups and individuals, such as the insurance industry and design engineers, led to the preparation of this summary that describes the various sources of data on freezing-rain and ice-storm damages. The benefits and limitations of each form of data are presented to help to guide potential data users.

PICTURE OF THE MONTH The Tristate Hailstorm: The Most Costly on Record

Abstract: The most damaging hailstorm ever recorded moved from eastern Kansas to southern Illinois during an 8-h period on 10 April 2001, depositing 2.5- to 7.5-cm-diameter hailstones along a 585-km path. A classic longlived supercell storm was the cause of the record hailfalls. The record-large hailswath size, large and often windblown hailstones, and movement over portions of the St. Louis and Kansas City urban areas led to $1.5 billion in insured losses. This tristate hailstorm and other adjacent hailstorms collectively created $1.9 billion in insured losses in a 2-day period, becoming the ninth most costly weather catastrophe in the United States since property insurance records began in 1949.

NOTES AND CORRESPONDENCE Urban Modification of Freezing-Rain Events

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.