A Report on Winter Snowpack-Augmentation

Cloud seeding to increase winter snowpacks over mountainous regions of the western United States have been in existence for almost 40 years. However, our understanding of the physical processes taking place in the clouds in response to this seeding and the expected precipitation increases are still subjects of great scientific interest and investigation. Recent field observations that have emphasized direct physical observations of winter clouds, their structure and liquid water content, as well as their response to the injection of glaciogenic seeding agents have added to our knowledge. These physical observations are helping to provide some insight into the mechanisms of precipitation increases, inferred from statistical analyses, that have been reported in certain winter orographic cloud seeding programs. This paper attempts to compare physical and statistical results, to show consistency, and to help provide limits to what one might expect when winter snowpack augmentation is applied within suitable cloud systems.