A CRITICAL-REVIEW OF THE AUSTRALIAN EXPERIENCE IN-CLOUD SEEDING

From 1947 to 1994 a number of cloud-seeding experiments were done in A ustralia based on the static cloud-seeding hypothesis. A critical anal ysis of these successive cloud-seeding experiments, coupled with micro physical observations of the clouds, showed that the static cloud-seed ing hypothesis is not effective in enhancing winter rainfall in the pl ains area of Australia. However, there is evidence to suggest that clo ud seeding is effective for limited meteorological conditions in strat iform clouds undergoing orographic uplift. In particular, two successi ve experiments in Tasmania show strong statistical evidence for rainfa ll enhancement when cloud-top temperatures are between -10 degrees and -12 degrees C in a southwesterly stream. The evidence for similar eff ects on the Australian mainland is more controversial. In the summer r ainfall regions of northern Australia, the extreme rainfall variabilit y makes it impossible to design a statistical experiment that can to b e evaluated in a reasonable time using currently available techniques. Rainfall enhancement in these regions remains inconclusive.