Science: Weather or Not

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After long and careful experimenting with dry ice and other artificial stimulants, the rainmakers are giving up. Hereafter, the Air Force announced this week, the rain will fall where & when it listeth.

Teaming up with the Weather Bureau, the Air Force has given scientific rainmaking a full-dress tryout. It set aside an 8-by-20-mile area near Wilmington, Ohio, and dotted it with ground observation stations. Powerful radar sets kept watch on the air above. When promising clouds appeared, an RB-17 Flying Fortress, loaded with dry-ice pellets, took off from Clinton County Air Force Base; an RF-61 Black Widow photographed the operation.

Results were poor. When solid winter cloud layers were sprinkled with dry-ice pellets (or water droplets or chemicals such as silver iodide), practically nothing happened. In no case did rain start falling unless it was already falling less than 30 miles away.

In experiments on the towering cumulus clouds of summer, results were hardly better. Seventy-nine of them got the dry-ice treatment, but only 18 produced any rain; in all cases except five, rain was already falling within 30 miles. Even in these five cases, there was natural rain 40 to 60 miles away.

Far from causing rain, the dry ice often produced the opposite effect: it made clouds dissipate. In rolling officialese, the Air Force and Weather Bureau expressed their joint disillusionment: "The responsible scientists of the project interpret the long series of experiments to mean that recently proposed artificial weather modification processes are of relatively little economic importance."