The Impacts of AgI Emission, Activation and Scavenging Rates from Ground-Based Generators on Cloud and Precipitation in Payette

Idaho Power Company has established an operational cloud seeding program using both ground-based AgI generators and seeding aircraft since 2002 to enhance the wintertime snowfall and subsequently the springtime stream flow for hydropower generation. During the past decade, the program has been expanded to cover the Payette, Boise, Woods, and Upper Snake River basins by deploying more ground-based generators and setting up more flight tracks. Finding suitable sites for ground-based generators in the wildness is not an easy task. With the goal of harvesting more snow under the constraint of available generator sites, Idaho Power wants to investigate novel ways to increase the seeding efficiency at each site. Increasing the AgI emission rate from each generator and putting extra generators are viable choices. To answer the questions of which method is more efficient and whether an optimum AgI emission rate exists to most efficiently enhance snowfall, NCAR scientists conducted high-resolution WRF sensitivity simulations of three ground seeding cases over the Payette region by varying the AgI emission rate, AgI activation rate and AgI scavenging rate from individual generator and adding more generators in the vicinity. It is found that increase of AgI emission rate is more efficient than adding new generators based on the model results. The details of this study will be presented at the conference.