INFLUENCE OF ATMOSPHERIC STABILITY LAYERS ON THE EFFECT OF GROUND-BASED CLOUD SEEDING, I. EMPIRICAL RESULTS

Abstract

creased. Neither A nor B is yet identified. The identification of these conditions A and B is, then, an important outstanding problem. A promising approach to this problem consists in a scrutiny of weather modification experiments already completed, with the primary purpose of verifying empirically the various a priori hypotheses underlying the current efforts at weather modification. The basic premise of rain stimulation with AgI seeding is the discovery by Vonnegut of the ice crystal nucleating property of the AgI smoke at temperatures below the threshold of -4?C. If the seeding is done from the ground, hopes of success depend upon the presence of strong updrafts capable of carrying the AgI particles into the supercooled parts of the clouds before the Agl is deactivated by photolysis. Ordinarily, temperature inversions and isothermal layers (stability layers, for short) are obstacles to convective updrafts and are expected to prevent cloud seeding from the ground from being effective. The purpose of the present paper is to provide evidence that, at least in mountainous regions, the mechanism of the effects of cloud seeding involves some unexpected