Summary Of Studies That Document The Effectiveness Of Cloud Seeding For Snowfall Augmentation

A brief summary of past research studies related to wintertime cloud seeding for snowfall augmentation has been compiled to illustrate what has been learned in those experiments that proved to be successful. The summary focuses primarily on physical studies, and on some randomized experiments that were accompanied by physical studies which verified aspects of the cloud seeding conceptual model. The important research areas covered include studies on: (1) the availability of supercooled liquid water, including its spatial and temporal distribution, (2) verifying the transport and dispersion of seeding material to clouds over target areas, (3) the microphysical changes caused by seeding with silver iodide and liquid propane, and (4) the precipitation increases that have been verified in physical studies and randomized experiments. The summary of results from past research details the specifics of the “strong suggestions of positive seeding effects” referred to in the 2003 report to the National Academies of Science entitled Critical Issues in Weather Modification Research. Although plentiful evidence regarding the effectiveness of cloud seeding is presented, it is also noted that further research on wintertime cloud seeding could provide answers to uncertainties that still exist, and also potentially benefit ongoing operational cloud seeding projects. Some recommendations for future research that take advantage of recent technological developments are presented.