Tracers for the study of scavenging by rain

The study of rain scavenging by means of tracers from crudely defined 'natural' sources has led to the idea that the resolution of physical problems of scavenging might be greatly improved by the use of artificially placed tracer. The selection of a suitable material to use in the study of strong convective systems, with measurement by neutron activation is discussed. The design, coordination and execution of a pilot experiment in a strong convective storm at Holdenville, Oklahoma, 30 May 1967 is recounted, and preliminary results of the neutron activation analysis are presented. Although statistics for the evaluation of natural background of the tracer material, indium, are not yet as numerous as desired, and the sample analyses are not all completed, the criterion for success of the pilot experiment, i.e., that the tracer be clearly identified in collected rain samples, is certainly met by the preliminary figures. (author)