Project Foggy Cloud 1

Foggy Cloud I was a series of experiments in observation, modification, and treatment of fog and stratus clouds conducted at or near the Arcata-Eureka airport, Humboldt County, Calif., from late March through mid- November 1968. A wide range of propsective seeding agents, including smokes, liquids, and powders, that were thought to offer promise for stabilization or clearance of fog were systematically screened by ground-based and airborne dissemination. The major emphasis was placed upon the elimination of fog rather than upon simply improving visibility. Those agents showing enough identifiable effects to indicate promise were investigated in detail and improved upon. Observations were made of fog characteristics, visual effects, changes in cloud physics parameters, and of the fallout from the fog. Hygroscopic smokes were found useful for intensifying, stabilizing, and forming fog and stratus. Hygroscopic powders, including sodium chloride, urea, and calcium chloride, were tried. Of these, calcium chloride showed the most promise, but testing was not completed. Hygroscopic liquids showed the most immediate results, and successful tests were made with ammonium nitrate in solution. In October, a solution consisting of ammonium nitrate, urea, and water was developed that was used in several very successful field trials.