KEY POINTS:

With the dry conditions over our South Island hydro lakes continuing (although we do have some rain forecast on Thursday night/Friday morning) it made me think about some research I had done a while ago about cloud seeding.

Cloud seeding is basically a form of weather modification, using chemicals that are dropped into clouds (by plane) or blasted into them (by rockets). The idea is to increase the amount of rain in clouds. For over 50 years now governments around the world have tried, and mostly failed, to cloud seed.

With the Olympics on the way China has been trying to find ways to cloud seed - not just because they need rain - but also to remove it from clouds to prevent rain ruining the opening of the Olympics. In fact, they've guaranteed fine weather for that historic day!

Spending 50 million US dollars a year as part of their "weather modification project". The project covers drought affected areas but also covers Beijing. The Chinese Government fires rockets into the sky and they believe they're achieving more rainfall leading to neighbouring countries to accuse them of "stealing rain". Of course rockets aren't the safest form of doing this and a number have gone off target and slammed into houses... and people.

There's another reason why the Chinese may be eager to guaranteed fine weather for the Olympics. August is their wet month with plenty of summer induced rain and the opening ceremony will be in an uncovered stadium. The plan is that the 50 million dollar a year research will mean that if rain clouds start to build before the ceremony then they'll fire rockets up and prematurely make the rain fall out of them - leaving the clouds rain-free by the start of the ceremony. So easy! Unfortunately at this stage it doesn't really work.

You might think that's a complete waste of money. I would have to agree if it's purely to ensure a dry Olympics, but if the Chinese actually manage to create a way to make rain fall from clouds can you imagine what that would mean for the drought affected areas of the world?

So what about other countries? In the United States cloud seeding trials are being carried out for a variety of reasons. In drought affected areas the government is seeding clouds to create rain. In airports prone to fog they are experimenting with ways to reduce the amount of fog and in states affected by large hail storms trials are being performed to reduce the size of hail.

At this stage nothing ground breaking has been uncovered. Some ski field operators in the US and Canada are also getting involved with trials to boost snow fall. Trials were also done in hurricanes but fears that they might 'get it wrong' and create worse hurricanes meant the trials were cancelled. I laughed when I researched that last piece: I could see Bush being involved in something like that.

In Australia some politicians have called for cloud seeding trials to start again. Trials were abandoned in the 1990s when the Labor Government came into power. Some testing has carried on in the Snowy Mountains but these politicians want to see that extended further. Inducing rain could be a life saver for many farms affected by Australia's arid conditions.

So what about New Zealand? Over twenty countries around the world are actively involved in weather modification trials. New Zealand is not one of them. According to NIWA, "So far we do not know enough about clouds and how to seed them, to be sure of the effects. We might make less rain when we want more, or more hail when we want less. So cloud seeding is not done in New Zealand". Trials were carried out in the 1950s using planes to drop dry ice in the clouds to bring rain to dry farms. The trial was unsuccessful.

A spokesman at MetService said back in the 1860s trials were conducted where cannons were used to shoot clouds in the hopes it would alter rainfall. Don't think that brilliant idea worked too well. In the 1970s the New Zealand Government dropped silver iodide from planes over Marlborough in the hopes they could create rain to ease droughts. But if the air is dry and there are no clouds then there is no point in seeding. It makes about as much sense as planting plant seeds on top of concrete instead of in the soil.

So whether cloud seeding can ever truly work is yet to be seen, but quite often it's the crazy ideas work. I say keep the research going so long as it doesn't remove much needed funds from more pressing weather projects.

Philip Duncan

For more information, visit The Radio Network's new Weather Watch Centre, the Newstalk ZB weather website or the NZ Herald weather section.