A Reevaluation of the Climax Cloud Seeding Experiments Using NOAA Published Data

Abstract

Some significant differences exist between the precipitation amounts for Climax 2NW (a station situated near the center of the target area in the Climax I and Climax II cloud seeding experiments) that have been used in previous analyses of the Climax experiments and NOAA published values for this station. Some of the interpolated 500 mb temperature assignments used in previous analyses also differ in category (i.e., ≥ ? 20°C or < ? 20°C) from those derived from NOAA sounding data. Using the NOAA data for precipitation at Climax 2NW, and the same control stations and series of statistical tests (which, in order of increased sophistication, are the seed/no-seed single, double and covariate ratios) used by the Climax Experimenters, the following results are obtained for interpolated 500 mb temperatures ≥ ? 20°C at Climax 2NW. For the exploratory Climax I experiments: seed/no-seed single, double and covariate ratios of 1.65, 1.14 and 1.25, respectively (compared to seed/no-seed single and double ratios of 2.17 and 1.32 for Climax 2NW and a seed/no-seed covariate ratio of 1.34 for the ?target group mean? precipitation reported by the Climax Experimenters). For the confirmatory Climax II experiment: seed/no-seed single, double and covariate ratios of 0.90, 1.04 and 0.90, respectively (compared to seed/no-seed single and double ratios of 1.24 and 1.17 for Climax 2NW and a seed/no-seed covariate ratio of 1.27 for the ?target group mean? precipitation reported by the Climax Experimenters). ? We conclude that the Climax II experiment failed to confirm that precipitation can be increased by artificial seeding in the Colorado Rockies.