Precipitation Evaluation of the North Dakota Cloud Modification Project

North Dakota interest in using weather modification to increase precipitation and reduce hail damage resulted in a managed cost-sharing program, the North Dakota Cloud Modification Project (NDCMP), being started in 1976. Our goal is to determine the effectiveness of NDCMP at increasing precipitation by using rain gauge observations of National Weather Service (NWS) Cooperative Observer Program (COOP) and North Dakota Atmospheric Resource Board Cooperative Observer Network (NDARBCON). The rain gauge analysis uses target and control regions. Precipitation is evaluated on a monthly and seasonal (June, July, and August) basis over the 41 years of the program. Multiple statistical analysis methods are used to examine available rain gauge data. Rainfall changes due to cloud seeding are small compared to natural variability and increases are hard to detect statistically because it is difficult to determine how much rain would have fallen in the target areas during NDCMP years if seeding had not occurred. A major cause of uncertainty is the limited rain gauge data available before the start of NDCMP, from which natural target/control relationships can be determined. Results show that McKenzie county has an increase in rainfall when compared to control counties to its south and southwest, likely due to cloud seeding efforts.