Evaluation of weather modification

A review of various procedures of evaluating the effects of weather modification operations used in past years is presented. Indications are the operators have made elaborate claims by simple comparisons of precipitation data from the target area after seeding and the average precipitation from past years of record. In some cases average isohyetal maps have been used. Such tests are thought to be extremely insensitive to show the desired effects. Statistical methods using multiple regression analysis and based on resulting inflow to reservoirs or streamflow is more practicable and protects against bias. With all evaluations certain assumptions must be made, either statistical, or physical processes. Seven necessary assumptions are listed for consideration. Reference is made to reports by the advisory Committee on Weather Modification and the National Science Foundation Reports on weather modification, of which 195 references on the subject are listed.