Cloud seeding experimental program in Rhodesia: 1974-75

D. McNaughton

Abstract


Using randomized instructions, isolated cumulus clouds were  either left alone or seeded near cloud top from an aircraft fitted  to fire pyrotechnic cartridges. The rain falling from both seeded  and untreated clouds was measured at cloud base using a rain  water collector. Seeded clouds with tops warmer than about      -10°C gave much the same rain as similiar non-seeded clouds.  With colder clouds, however, the average rainfall was greater   on seeded than on non-seeded occasions. When rain falling  earlier than 40 minutes after the start of the experiment was  excluded from the calculations, then the apparent bias in favour  of the seeded clouds in the two-season period 1973-74-75 was  significant at the 10% level. Again excluding early rain, the six  heaviest falls all came from seeded clouds; the probability that  this was pure chance is less than 0.04. However, there were  also several seeded clouds which failed to rain.

Keywords


Weather Modification Research

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