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- Author or Editor: Stanley A. Changnon Jr. x
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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.
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.
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.
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.
Abstract
Temporal and spatial relationships between thunderstorms (events) and flashes were investigated using data for 1983–85 for 25 first-order stations (10 in the West and 15 along the East Coast). Thunder events were compared with flashes within three ranges: 5 km, 10 km, and 20 km, around each station. Cluster analysis revealed six geographic regions: Florida, Southeast (South Carolina, Georgia), Mid-Atlantic (Virginia, Maryland Pennsylvania), Northeast (New York and New England), Rocky Mountains, and an intermontane area.
Periods of multiple flashes not within thunder events and within 10 km of a point (most realistic for audibility), revealed that 10% to 20% (depending upon region) of all thunderstorms were missed. Also, 13% (Rockies) to 44% (Mid-Atlantic) of all thunderstorms have recorded durations too short (missed flashes before their reported start), and the average underestimated durations were from 55% (Northeast Mid-Atlantic) to 26% (Rockies). Flashes isolated in time and space, due to locational errors, represent 1% of all flashes in the east and 3% to 5% in the west where the data are poorer. Errors in flush data appear minimal but the errors in thunder events are sizable.
Thunder events and flash frequencies related well based on major features in their average areal patterns and their between-year changes at stations. Correlations of fishes with events varied; their annual point frequencies had coefficients of +0.83 (east) and +0.67 (west). Durations of events and Bash frequencies were poorly correlated with skewed distributions (often large flash frequencies in a few storms). The percent of all recorded flashes (within 10 km) in thunder events varied from 28% to 44% at western stations and from 13% to 20% at eastern stations. Thunder events with ≥ 1 flash varied widely, from 71 % of all events at Washington, D.C. to 30% at Boston.
Major east-west differences existed in the frequency of thunder events with flashes, reflecting poorer audibility of thunder in the west. Part of the difference is due to flash recording problems in the west, leaving flash frequencies that are underestimates of the true values. latitudinal distributions were marked with north-to-south increases in thunder events and their durations, frequency of flashes, and number of flashes not in events. More missed flashes in the south suggested that atmospheric conditions in northerly U.S. latitudes enhance audibility. With a 20-km sampling radius, between 6 (Northeast) and 23 (Southeast) thunder events are not recorded yearly, but these averages drop to 1 (Northeast) and 4 (Southeast) based on flashes within 5 km. The data on thunderstorms is generally poor from two perspectives: 1) the recorded data miss sizable numbers of storm events, and 2) when recorded, 30% to 50% often underestimate durations based on nearby lightning activity.
Abstract
Temporal and spatial relationships between thunderstorms (events) and flashes were investigated using data for 1983–85 for 25 first-order stations (10 in the West and 15 along the East Coast). Thunder events were compared with flashes within three ranges: 5 km, 10 km, and 20 km, around each station. Cluster analysis revealed six geographic regions: Florida, Southeast (South Carolina, Georgia), Mid-Atlantic (Virginia, Maryland Pennsylvania), Northeast (New York and New England), Rocky Mountains, and an intermontane area.
Periods of multiple flashes not within thunder events and within 10 km of a point (most realistic for audibility), revealed that 10% to 20% (depending upon region) of all thunderstorms were missed. Also, 13% (Rockies) to 44% (Mid-Atlantic) of all thunderstorms have recorded durations too short (missed flashes before their reported start), and the average underestimated durations were from 55% (Northeast Mid-Atlantic) to 26% (Rockies). Flashes isolated in time and space, due to locational errors, represent 1% of all flashes in the east and 3% to 5% in the west where the data are poorer. Errors in flush data appear minimal but the errors in thunder events are sizable.
Thunder events and flash frequencies related well based on major features in their average areal patterns and their between-year changes at stations. Correlations of fishes with events varied; their annual point frequencies had coefficients of +0.83 (east) and +0.67 (west). Durations of events and Bash frequencies were poorly correlated with skewed distributions (often large flash frequencies in a few storms). The percent of all recorded flashes (within 10 km) in thunder events varied from 28% to 44% at western stations and from 13% to 20% at eastern stations. Thunder events with ≥ 1 flash varied widely, from 71 % of all events at Washington, D.C. to 30% at Boston.
Major east-west differences existed in the frequency of thunder events with flashes, reflecting poorer audibility of thunder in the west. Part of the difference is due to flash recording problems in the west, leaving flash frequencies that are underestimates of the true values. latitudinal distributions were marked with north-to-south increases in thunder events and their durations, frequency of flashes, and number of flashes not in events. More missed flashes in the south suggested that atmospheric conditions in northerly U.S. latitudes enhance audibility. With a 20-km sampling radius, between 6 (Northeast) and 23 (Southeast) thunder events are not recorded yearly, but these averages drop to 1 (Northeast) and 4 (Southeast) based on flashes within 5 km. The data on thunderstorms is generally poor from two perspectives: 1) the recorded data miss sizable numbers of storm events, and 2) when recorded, 30% to 50% often underestimate durations based on nearby lightning activity.
Abstract
An understanding of applied climatology and its information-generating research requires recognition of the total cause-and-effect spectrum including the issue detection, the research effort pursued, the type of product, the users, and their applications of findings. Twenty climatic information studies done at the Illinois Climate Center in 1977-79 are reviewed to illustrate why they were done, often as a result of general inquiries or specific requests, and a few of their key results. The studies each required from weeks to months to complete. Most users of the results fell in two general classes, government or business-industry. The studies revealed applications in three areas: the design of facilities, the planning and/or operations of facilities and activities, and the climatic assessment of weather extremes.
Abstract
An understanding of applied climatology and its information-generating research requires recognition of the total cause-and-effect spectrum including the issue detection, the research effort pursued, the type of product, the users, and their applications of findings. Twenty climatic information studies done at the Illinois Climate Center in 1977-79 are reviewed to illustrate why they were done, often as a result of general inquiries or specific requests, and a few of their key results. The studies each required from weeks to months to complete. Most users of the results fell in two general classes, government or business-industry. The studies revealed applications in three areas: the design of facilities, the planning and/or operations of facilities and activities, and the climatic assessment of weather extremes.
