Evaluation of rain making experiments in Utah

After three years of operations a weather modification project is studied and an evaluation is made over an area covering 200 square miles in Southern Utah. Use is made of Electronic Data Processing equipment to evaluate precipitation data from 120,000 Weather Bureau observations of daily rainfall amounts from the state. The process involved a statistical comparison of data from within and without the target area, also the inter-relationship between stations. Many problems complicate the study: the changing of location of silver iodide generators, the addition of more generators, the silver iodide drifting out of the target area and effecting station records in remote areas. It became difficult to establish a constant set of guidelines for evaluation. The studies are continuing for reporting, provided funds are available.In discussion Mr. Boyd E. Quate pointed out the difficulties of evaluating cloud-seeding operations by virtue of so many projects in operation over the arid states that the long distance effect of silver iodide particles may affect precipitation on an inter-state basis.