Large Scale Dynamic Effects of Cloud Seeding

摘要

The report covers a three and one half year study of the Large Scale Effects of Cloud Seeding. Included in this program was a statistical analysis of four long term operational cloud seeding projects and two randomized research type projects and finally a pilot field program to test the hypotheses developed in the statistical phase of the contract. The statistical analysis of past operational and research seeding projects showed considerable evidence that areas 70 to 150 miles downwind from the nuclei source were receiving increased precipitation during cloud seeding operations. In many cases the increases in the downwind area was equal or greater than those in the intended target areas. A field program conducted during the 1968-69 winter season essentially confirmed this finding. The field program consisted of a detailed analysis of raingage records from a dense gage network in and downwind from a randomized research program in Santa Barbara County, California. The observation and seeding unit employed on the combined project was a convective band embedded in a general storm system. The seeding was accomplished with a single ground source using a high output pyrotechnic device. (Author)