Growing cyclone risk sparks radar mission

By SIMON COLLINS science reporter

Auckland University scientists are going to Queensland to study tropical cyclones in case global warming starts sending them our way.

Led by physics professor Geoff Austin, they are building a mobile radar device to measure wind speeds and rain inside a cyclone.

They plan to speed up the north Queensland coast in a four-wheel-drive to place the radar and rain gauges on exposed hilltops before a cyclone hits.

"We'll be running in, bolting everything down and running out, and after it's all over we'll go back and see whether we were lucky or not," Dr Austin said.

"Normally the distribution of rain gauges is pretty sparse and the power goes out and trees are down. So we'll be putting a rain gauge several hundred metres up, and no one has ever done that for a tropical cyclone."

The research, paid for by the New Zealand and Australian governments, could have immediate value for northern New Zealand if rising world temperatures shift the summer cyclone belt southwards.

Cyclone Zoe hit the Solomon Islands a month ago with reported wind speeds up to 350km/h, although MetService weather ambassador Bob McDavitt says the damage pointed to speeds more like 170km/h.

Auckland's Sky Tower is built to withstand 250km/h winds, the strongest yet recorded in New Zealand.

Dr Austin said people building houses in exposed places should consider precautions such as using two nails instead of one to secure roof tiles or metal roofs.

"I am building a house in a fairly exposed location at Waipu and I am getting everything double-nailed."

He said cyclones usually developed only at sea surface temperatures above 26C - now north of a line midway between New Zealand and Fiji in the summer peak. Summer sea temperatures around northern New Zealand are now about 20C.

World average temperatures have risen about 0.4C since 1860, and are forecast to rise 1.4C to 5.8C by 2100 through the "greenhouse effect" partly caused by carbon dioxide from car fumes and industry.

"The whole region here could really warm up 2C in 100 years," Dr Austin said. "But there is more than a 2C inter-annual variability, so the worry is that would make it two plus two. If we are 20C now, that takes us to 24C, which is getting uncomfortably close to 26C.

"More importantly, the 26C isotherm could come quite a few hundreds of kilometres further south, and that would still have a pretty wound-up tropical cyclone coming down our way."

His initial research in a subtropical storm that hit Gisborne several years ago found that there was much more rain immediately behind even small hillocks - suggesting that the effects on New Zealand's relatively high hills could be worse than on low Pacific atolls.

"Most meteorology models wouldn't model the terrain to less than 50km. We are seeing stuff that's happening at the 1km scale."

Dr Austin and Auckland University technicians have designed a mobile radar costing about $60,000 plus labour, compared with Swiss gear used by US laboratories costing more than US$1 million.

"We have a lot less research money here but we have very good technical staff," he said.

"The new one is generating considerable interest and we may well be exporting them. I suspect we could sell half a dozen if we worked at it.

"We have talked about partnerships with local companies but it requires a range of skills from welding to radar electronics and computers. We happen to have that bizarre set of people on the staff.

"I would be interested to have communication with any company that thought they could build them."

* Email: g.austin@auckland.ac.nz

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