Evidence of persistence or cross-contamination in cloud seeding experiments

TitleEvidence of persistence or cross-contamination in cloud seeding experiments
Publication TypeConference Proceedings
Year of Conference1968
AuthorsWarburton, J. A., and Young L. G.
Conference Name36th Annual Western Snow Conference
Series TitleProceedings of the 36th Annual Western Snow Conference
Date PublishedApril 1968
PublisherWestern Snow Conference
Conference LocationLake Tahoe, Nevada
KeywordsCloud seeding effectiveness, Cloud seeding evaluation, Weather modification

One hundred and fifty samples collected during 1966-67 have been analyzed for silver content using thermal neutron activation methods. The samples were collected in five separate regions of the western United States. In two of the locations where extensive randomized silver iodide seeding was occurring, with seeding periods of one day, there is evidence of persistence of silver in the atmosphere in unseeded situations. Silver, in relatively high concentrations, was present in specific storms which yielded precipitation in an unseeded region. It is speculated that this silver originated in cloud seeding regions upwind of this unseeded area. Results also provide evidence that silver iodide released from the ground in one mountainous seeding area is not arriving in the target area precipitation. This is in strong contrast to results in two other similar seeding projects where high concentrations of silver are observed.