RESUMEN
Measurements of cloud condensation nuclei were made from small samples of stratospheric air taken from a U-2 aircraft at altitudes ranging from 13 to 19 kilometers. The measured concentrations of nuclei both in and outside the plume from the May and June 1980 eruptions of Mount St. Helens were higher than expected, ranging from about 100 to about 1000 per cubic centimeter active at 1 percent supersaturation.
RESUMEN
Visibility in warm fog produced in a 600-cubic-meter chamber was increased by factors of 3 to 10 by seeding with carefully sized sodium chloride particles. As little as 1.7 milligrams of salt per cubic meter was effective. Extrapolation of these results indicates that clearing a suitable landing zone for aircraft would not involve prohibitive amounts of seeding material.