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Stanley A. Changnon Jr.

The winter of 1977–78 was the worst, on the basis of both low temperatures and snow, on record in Illinois and many other areas of the Midwest. Representatives of 70 households in central Illinois participated in a detailed study of how the extreme cold and snow affected individuals. The average added cost was $93 per individual, largely to residences and vehicles, and extrapolation of this to all Illinois citizens results in an estimated statewide cost in excess of $1 billion. This was compounded by a wide variety of personal inconveniences, worries, extra work, and injuries. There were no deaths in the sampled group but 52 Illinoisans were killed by the 18 winter storms. For those living in rural areas beyond the city of their employment, costs and inconveniences were greater. The average individual cost was $120, and rural dwellers experienced more travel problems, more delayed services, and more absences from school and work.

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Stanley A. Changnon Jr.

A review of recent research in the United States concerning urban effects on precipitation has revealed that relatively few studies have been performed. The lack of densely spaced precipitation stations with good historical records, inadequate instruments for airborne measurements of the mechanisms that affect precipitation systems, and the difficulties associated with separating orographic, maritime, and gage-exposure effects are the primary reasons for so little research.

However, certain climatological studies of four variously sized cities in the midwest and two large cities in the east have shown apparent urban-produced increases ranging from 5 to 16% in annual precipitation and rain days, with 7 to 20% increases in summer thunderstorm days. Substantially greater increases in precipitation, thunderstorms, and hailfalls, 31 to 246%, have been shown in a recent study of an area downwind from a major steel mill complex. The available results show little evidence of urban effects on the occurrence of excessive rainfall rates or on the amount of snowfall, although little study of these conditions has been performed.

The recent development of airborne nuclei measuring instruments has led to selected measurements of condensation and freezing nuclei over several urban areas. These furnish evidence that urban-induced nuclei concentrations are high and probably sufficient to produce the observed changes in precipitation, whereas other American studies have indirectly shown the importance of the urban thermal effects. The study of inadvertent precipitation increases from urban areas has particular significance for planned weather modification since the amounts of the inadvertent increases approximate those confirmed for planned experiments. The results of the urban studies may indicate the effectiveness of ground-based seeding, the possibility of successful increases in all seasons, the likelihood of thunderstorm and hailstorm increases with rainfall increases, and the need for dense raingage networks to adequately determine the area and amount of increase.

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Stanley A. Changnon Jr.

A notable increase in precipitation, moderate rain days, thunderstorm days, and hail days has been occurring since 1925 at La Porte, Ind. Since La Porte is 30 miles east of the large complex of heavy industries at Chicago, there is a strong suggestion that the increases in precipitation conditions are due to inadvertent man-made modification.

If these increases are real, they serve as a good measure of the increase in convective precipitation that man could attain, at the same time pinpointing an excellent site for future meteorological studies of the exact causes of the increases. If the increases are fictional and result from exposure changes and observer error, they serve as an indication of the sizeable errors that may exist in some of our long-term climatological records.

The increase at La Porte is sizeable: during the 1951–1965 period La Porte had 31% more precipitation, 38% more thunderstorms, and 246% more hail days than did surrounding stations. Since 1925 the year-to-year fluctuations in the annual and warm season precipitation at La Porte show agreement with the temporal distribution of steel production in the Chicago area. After a careful assessment of all available climatological data, it was concluded that these sizeable increases were real and not fictional.

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Stanley A. Changnon Jr.

A midwestern group of 46 scientists and 16 nonscientists were polled at a recent AMS meeting about their beliefs on climate change, the CO2 issue, and the overall importance of these issues. Most indicated a belief in a trend to a climate that is colder, wetter, and has more weather variability. The group also indicated that the reports on CO2 were confusing to them and especially to the public. Finally, they indicated that the ongoing climate shift has been important to their lives.

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Stanley A. Changnon Jr.
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Stanley A. Changnon Jr.

Abstract

Historical (1901–85) summer (June–August) rainfall data in central Illinois were used to construct three typical rain conditions: one representing the typical dry summer (based on the driest 20% of the summers of the past 85 years), a typical wet summer (from the 20% wettest), and the near-average summer rainfall conditions (the 20% nearest the long-term average). Monthly rain totals for each type were established first, then daily rain frequencies were used to define all individual rain day amounts, and historical rain-day amounts by date were used to assign rain days to dates throughout the three types of summers. In-day conditions relating to rainfall rates, time of rain, and durations were constructed for each day of rain. The resulting three summer rainfall conditions are being used to guide applications of water onto agricultural test plots (protected from natural rains) to measure crop yield effects from weather modification but the approach and system could serve other applications like effects of climate change.

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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.

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.

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STANLEY A. CHANGNON JR.

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.

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STANLEY A. CHANGNON JR.

Abstract

Research concerning long-term temperature changes in the United States has shown the need to adjust measured increases in the 1901–1950 period to remove the effects of environmental changes. Unique long-term 3-ft. soil temperature data at Urbana, III., provide a measure of the natural increase in temperature in the 1903–1947 period and also permit an evaluation of the increase shown by the air temperature at Urbana. The increase in mean annual soil temperatures between 1903 and 1947 amounted to 1.2° F. The mean annual air temperatures during this period inercased 2.3° F., but when adjusted statistically to remove environmental effects, the natural increase in the air temperature was 1.1° F. Thus, at Urbana, the adjusted increase in air temperatures appears to be substantiated by the increase shown by the 3-ft. soil temperature data.

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