Snow storm provides crucial information for scientists

While South Islanders are being warned to stay at home and prepare for the biggest storm predicted since 1992, NIWA scientists will be putting on their wet weather gear and heading out to measure snowfall.

Throughout the storm NIWA is mobilising teams in the South Island to gather much needed information about snowfall at low elevation.

Hydrologist Dr Christian Zammit calls it snow mobilisation, where snow experts go out gathering snow related information, such as depth and vertical density at specific locations.

"We have very little New Zealand specific information about snowfall at low elevation so gathering information from this storm is important. In the future this information could help prevent building collapses, stock loss and indicate areas that power lines are vulnerable to ice, snow and wind."

Dr Zammit is also assisting GNS Science by looking at the amount of groundwater that is produced from snow melt. This water has the potential to create landslides or to saturate the soil making it vulnerable to flooding if heavy rain strikes.

Since 2009, NIWA scientists have been taking recordings of ground snow below 300 metres to gather data that is relevant to New Zealand snow conditions at low elevation. Historically information used locally has been based on snow standards from Australia and America, but what is needed is local information.

"We still need a lot more information and that is why we are sending all our teams out, who are well prepared for working in severe weather conditions.

"We need to better quantify how snow ice and wind interact with infrastructure, such as buildings and power line networks."

Dr Zammit says the information he is gathering about snow depth and density is important for the Building and Housing Group, at the Ministry of Business Innovation and Employment, to inform building standards and codes. The Group needs accurate information about how ground snow is translated into load on the roof.

"We have adapted a weather model to predict snow amounts. In the future this tool could be used to help alert utility operators of possible infrastructure damage from snow and the need to have repair crews on standby."

For the next few days NIWA is predicting the heaviest snow falls will be inland and in north Canterbury, therefore the Christchurch-based team is preparing to make measurements in these areas as conditions permit.

The public can also help NIWA gather snowfall information by measuring the snowfall in areas of low elevations around their homes.

For instructions on how to measure snowfall, and how to send the information in to NIWA, go to the webpage How Deep is the Snow at your Place?.

We encourage people to, in all circumstances, put safety first and follow instructions issued by the Ministry of Civil Defence and Emergency Management, before venturing outdoors.

Haden McDermott
NIWA staff in Tekapo taking low elevation snow measurements. [Haden McDermott]
Haden McDermott
NIWA cars snowed in at Tekapo. [Haden McDermott]
Nelson Boustead
NIWA's Christian Zammit measures snow depth in Christchurch. The difference between wet and dry snow for a given depth, he says, can be as much as 500kg per cubic metre. [Nelson Boustead]
Haden McDermott
The gauge used to take snow measurements. [Haden McDermott]