Brian Williams
March 03, 2008

BRISBANE has had such a wet summer it has stymied efforts by scientists to determine if cloud seeding will work in subtropical conditions.

Another quirky problem is that by washing particulates out of the air, the rain has virtually made atmospheric conditions too clean for the tests.

Cloud seeders prefer to work in dirty air, air with particulates to which silver iodide crystals or salts fired into the cloud will stick.

When they stick, ice accumulates, snowflakes form and then melt to become rain.

Since December, the team has flown about 100 hours over the Brisbane Valley chasing super-cooled clouds, with about half that time spent seeding and the rest measuring background atmosphere.

National Centre for Atmospheric Research scientist Roelof Bruintjes said yesterday that for unequivocal results to be provided to the State Government on the $7.6 million, four-year project, he needed to take measurements in drier times.

“We’ve been dealt a very wet year,” Dr Bruintjes said. “It’s given us a good snapshot but we need to find out how seeding will go in a drier or more normal year.”

“It’s one of those things. If it rained this much all the time, they wouldn’t have any water problems and they wouldn’t want cloud seeders.”

Flights will continue until the end of this month.