Abstract
Daily observations of the surface concentration of ice nuclei have been made for three summers in Missouri as a part of Project Whitetop. The observations were taken with a nucleus counter of the expansion type. Ice nucleus counts varied considerably from day to day and from hour to hour; they were greater, on the average, during periods with southerly winds and high amounts of precipitable water overhead. Scheduling of observations also permitted an analysis of possible effects of cloud seeding in the area. The seeding utilized silver-iodide smokes from aircraft at distances of 25 to 45 miles from the nucleus counter. In the average, the seeded periods showed a slightly increased nucleus count at the ground, but the increase was small when compared with natural variations in the nucleus count. An indication was found that the slight increase in count during cloud seeding may persist into the day following that upon which the cloud seeding takes place.
