Further studies of the whitetop cloud-seeding experiment.

By means of two stratifications of experimental days of the Whitetop Project-into categories E and W and into categories air mass and frontal-the effects of cloud seeding on precipitation downwind, upwind, and to the sides, up to 180 miles from the seeding line, were investigated. No significant effects were found for W and frontal days. On the other hand, for E and airmass days, significant and highly significant apparent effects of seeding were found in all directions and in areas at distances up to 180 miles. All these significant apparent effects are negative, the largest of them indicating that seeding reduced precipitation to one quarter of its unseeded value.