Twelve Years of Cloud Seeding in the Necaxa Watershed, Mexico

Abstract

The Mexican Light and Power Company has conducted cloud-seeding experiments with silver iodide from 1949 to 1962 (excepting 1952) over the Necaxa watershed and also, during the last 7 years, over the upper Lerma river valley. The present report is concerned primarily with the experiments carried out in Necaxa, with only passing reference to those conducted in the Lerma watershed. Most of this report is concerned with the evaluation of the results of the experiments by linear regression and rank list methods. Both methods show fair agreement in indicating a positive effect of seeding. In particular a mass analysis and contingency tables are presented which throw light on the effect of silver iodide upon several classes of rainfall.