SOURCES OF DATA There were five primary sources of information which may be used for a qualitative evaluation of weather changes attributable to detonation of high yield devices at the Pacific Proving Ground: 1. The network of surface and upper air observation stations. This network consisted of regularly reporting weather stations at Eniwetok, Kwajalein, Majuro, Ponape, Kusaie, Truk, Wake, Marcus and spasmodically reporting stations at Rongerik and Tarawa. These stations were within an area bounded by the equator and latitude 25° N., and longitudes 150° E. and 175° E. Eniwetok was approximately in the center of this trapezoid which has an area of about two-thirds that of the continental United States. 2. weather surveillance over approximately this area. 3. Limited radar coverage. Radar used was the SPS-6, installed on the command ship for the control of aircraft. It was not primarily used for weather surveillance, and sketches of shower distribution as show on the SPS~6 scope were possible only whenthe scope was not being used to vector aircraft. 4. Visual sky and shower observation. Immediately prior to, and for a period of several hours following each shot, visual observations of sky and shower conditions were taken by personnel of the Task Force Weather Central. These observations were necessarily from a point Upstream from the area where a major portion of the radioactive fallout viii bot eee eee Z Aerial weather reconnaissance aircraft which maintained