Showing papers by "Stanley A. Changnon published in 1973"

Precipitation Modification By Major Urban Areas

Abstract: Historical weather records at eight American urban areas of varying size, type, and climate were studied for indications of inadvertent precipitation modification. The six largest cities all had experienced warm seasonal rainfall increases of 9 to 17% during the 1955–70 period. The increases in the Midwest cities occurred largely with cold frontal systems, but in the coastal cities they were largely during air mass (non-frontal) conditions. The Midwest increases also were found to occur as enhancement, not initiation, of moderate to heavy rain days. Significant increases in summer thunder-day frequencies (13 to 41%,) and hail-day frequencies (90 to 450%) were found at the six largest cities, and the increases occurred largely in the morning hours. The typical locations of maxima in the Midwest cities were thunder over and near the city, and rain and hail 25 to 55 km downwind. The maxima of all events in coastal cities were in or near the city. Overall, the results suggest that urban precipitation...

Weather Modification in Up Or Down

Abstract: Weather modification activities in 1972 are reviewed to identify the major new projects, the major new findings, the major problems, and what these all mean for this exciting, often controversial science. The major new projects revealed a decided increase in interest and funding at the state and local levels, as well as new thrusts in federal programs. Non-governmental support of weather modification research and operations performed by American commercial firms exceeded $8 million, representing about 25% of the total expenditure on weather modification in the United States in 1972. Major new findings related to a variety of laboratory, instrumental, and field activities concerning planned modification of precipitation, hail, and warm fog, and also to inadvertent modification of clouds and rainfall. Several controversies regarding weather modification arose in 1972, but they all revolved more around the questions of its desirability or methodology, rather than whether it could be done. In general, 1972 wa...

Inadvertent Weather and Precipitation Modification by Urbanization

Abstract: Urban-industrial complexes produce measurable inadvertent modification of all weather conditions and specifically significant increases in the precipitation conditions of interest to hydrologists and urban planners. In, and immediately downwind of, major urban areas the annual precipitation may be increased from 5–30%, the annual thunderstorm frequency is increased 15–30%, the heavy (2-in.) daily rainstorm frequencies are increased by 20–40%. Increases in local runoff may be from 15–20%. Local crop yields may be increased 2–10% by this rain modification.

Precipitation Enhancement Program for Illinois

Abstract: Study of possible solutions to such problems has shown that precipitation enhancement is one potential solution. The 5-yr planning and research program is composed of 10 studies to obtain information adequate to decide and design a future experiment. The current Illinois Precipitation Enhancement Program is composed of four study-activity areas addressed to answering the question of desirability, five study-project areas concerned with the scientific feasibility of obtaining useful rain increases, and one that summarizes the results with regard to the design of future enhancement experiments. The desirability studies include the potential economic benefits, ecological effects, public information, and legal aspects so that Illinois citizens can understand and make wise judgments relating to weather modification. The five scientific feasibility studies involve cloud and storm sampling, numerical modeling, consideration of downwind effects, seeding technologies, and relevant chemistry measurements.