Abstract
The North Dakota Cloud Modification Project (NDCMP) is a state-managed, cost-sharing weather modification program with a primary goal of reducing crop hail damage and a secondary goal of increasing precipitation. North Dakota has conducted NDCMP in western North Dakota since 1976. This analysis evaluates the 1977–2018 cloud seeding impact on rain gauge measured precipitation using an exploratory historical target/control statistical analysis. Three counties where seeding is conducted each year are target areas: McKenzie, Bowman, and Ward. Neighboring counties where little or no seeding occurred are control areas. Averages of available daily rain gauge measurements provide monthly and seasonal (June–August) area precipitation amounts for the target and control areas. Double ratio statistics are determined using the pre-NDCMP period of 1950–1975 and the NDCMP period of 1977–2018. The statistics use the McKenzie and Bowman target areas paired with four different control areas, along with the Ward target area paired with one control area. Six of eight McKenzie and Bowman target/control pairs have double ratios (1.01–1.12) possibly indicating higher target area precipitation during NDCMP. Additionally, two of eight ratios have a 95% statistical chance of being greater than 1.0. The Ward target/control comparison indicates no enhancement. The average of all nine target/control ratios is 1.03, consistent with a modest overall precipitation enhancement by NDCMP hail suppression operations.
Highlights
North Dakota farmers have been interested in using weather modification to increase precipitation since the 1930s; the idea of weather modification dates back to the 1800s (Smith et al 2004)
Weighted pre-North Dakota Cloud Modification Project (NDCMP) rainfall amounts for target areas versus controls for June, July, August, and seasonal total showed a natural variation in rainfall prior to the NDCMP
While there were cloud seeding experiments ongoing prior to the start of the NDCMP, it is not believed that those efforts had a significant effect on area rainfall during that time
Summary
North Dakota farmers have been interested in using weather modification to increase precipitation since the 1930s; the idea of weather modification dates back to the 1800s (Smith et al 2004). Weather modification projects started in the 1950s within North Dakota, where ground-based generators were used to deliver seeding agents into clouds. By the 1960s, aircraft-based delivery of seeding agents was the preferred delivery method. A managed cost-sharing program, the North Dakota Cloud Modification Project (NDCMP), was started in 1976 (Schneider and Langerud 2011) with the primary goal of hail suppression to reduce crop loss. It quickly added a secondary goal of rainfall enhancement. NDCMP currently conducts hail suppression and rain enhancement operations over western North Dakota in two areas during the months of June, July, August, and occasionally early September
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