The potential use of summer rainfall enhancement in Illinois. Part II: Integration of factors affecting enhancement projects and future research
- Illinois State Water Survey, Champaign (United States)
Rain-yield findings were integrated with the average incidence of rain days and areal distribution of rain in a potential rain-modification area in Illinois to simulate regional aspects of a cloud-seeding project over a 13,000-km[sup 2] area. Potential seeding opportunities are limited because clouds cannot be effectively seeded at night, and 46% of all rain events occur at night. Further, 32% of all remaining rain events occur with severe weather warnings when Illinois law does not allow seeding. The number of candidate rain periods for modification is reduced from a regional average of 31 days to 11 days. Yield increases from the best treatment, based on all years' performance are further reduced regionally because on 53% of the moderate rain events, 50% of the simulated project area receives less than the minimum moderate rain level. These factors combine to reduce yield gains from 20% to 43% of the yield responses found in the 1987-91 field trials. The effects of the resulting crop-yield changes over the simulated project area ranged from an average annual increase of $3.4 million to an average decrease of $2.6 million per year. The estimated annual cost of a quality cloud-seeding project over the area is $1 million. Regional benefits could be larger if summer rainfall forecasts were sufficently accurate to allow selection in those summers when natural rainfall met crop water needs. The 1987-91 field trials sampled only 30% of the growing conditions that occur in Illinois. The rain-modification results are only estimates of the possible outcomes from an added rainfall. They reveal clear needs for research relating to weather modification in the humid climate of the corn belt. More field trials are needed to define crop yield-rain relations in other types of growing seasons. Methods for seeding clouds at night must be developed if agriculturally useful increases are to occur. Increased attention should be given to seasonal forecasting research. 12 refs.
- OSTI ID:
- 6534372
- Journal Information:
- Journal of Applied Meteorology; (United States), Vol. 32:3; ISSN 0894-8763
- Country of Publication:
- United States
- Language:
- English
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