We already know Wellington is one of the world’s windiest cities – now a new scientific study will measure how much the capital’s infamous winds speed up as they howl through the landscape’s natural tunnels.
National Institute of Water and Atmospheric Research principal scientist Mike Revell said a “speed-up effect” was being created in wind tunnels around the city, where gusts could be two or three times as strong as those felt in other areas.
“If you blow a wind over a flat piece of land, it’s the same everywhere. If you put hills or mountain, it gets slowed down in some parts but sped up in others.”
While Monday’s high winds saw police urge motorists to take care driving over the Rimutaka Hill – where gusts reached 146kmh at the summit – the strong winds offered the research team its first set of data.
Researchers have set up specialist wind-speed monitors on five-metre-high masts in Belmont Regional Park, and another on an existing 70m mast.
They will also be using acoustic wind- measuring devices, which record sound waves to produce a profile of wind conditions.
Wind funnelled through the Cook Strait contributed to Wellington’s weather, Dr Revell said, but the wind around any of the city’s peaks – such as Mt Victoria, Makara or Tinakori Hill – could be magnified by two or three times as the surrounding landscape caused it to accelerate.
“It’s one of the windiest cities in the world. Mostly, people don’t put cities in such windy spots.”
Dr Revell said the data would better inform future decisions about how high new structures were built in different parts of the city. “At the moment, those building codes have been put together from experience and theory.”
As there was very sparse data on “speed-up effects” worldwide, the team’s research would be used in building designs both here and overseas.
Opus International Consultants had created a miniature wind tunnel for the study, Dr Revell said. “We’ll put a scale model inside, it’s about 40 or 50 metres long, and we’ll blow wind through it.”
Data collected from the masts’ monitoring equipment would then be compared to speeds through the wind tunnel.
Niwa scientists are being joined by Auckland University researchers on the study, and also GNS Science. Their work will feed into the regional “Riskscape” project, in which a profile is being built of each area’s natural hazards.
The results could also help decide where to place wind turbines, as small spatial differences in locations can produce significantly different outputs.