Cloud seeding experimental program in Rhodesia: 1974-75
Keywords:Weather Modification Research
AbstractUsing 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.
Technical Notes and Correspondence
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