A Simulation of Alberta Cumulus

Abstract

A two-dimensional cloud model was used to simulate an Alberta, Canada, seeding experiment that was conducted on 24 July 1979, by the Alberta Research Council. The simulation reproduced some of the characteristics of the silver iodide seeded cloud in the actual case studies. This simulated cloud was also allowed to develop naturally and, in a third simulation, as a CO2 seeded cloud. A stratus layer was reproduced in the simulations, as well as the cloud used in the seeding simulations. The model was similar to those in previous papers, but there have been enhancements. Cloud ice was simulated as a bulk field with the total mass of ice; this was the sole predictor in the previous papers, while here an additional predictor, total number of ice crystals, was added. In the seeding simulations, the silver iodide produced a longer lasting seeding effect than the carbon dioxide. The carbon dioxide fell out of the cloud in minutes, while the silver iodide was carried around by the air flow for an indefinite period until completely activated. In the actual seeding cases, the silver iodide appeared to produce a long lasting effect also, while the carbon dioxide was a short term effect. The precipitation was produced by the seeding in the simulation with no precipitation forming in the untreated cloud.