Scientists focus on Southern Alps weather

By Brendon McMahon

Monitoring for the international weather research project based at Hokitika Airport will ramp up this week once specialised equipment is set up.
Hokitika is hosting a segment of a wider New Zealand project dubbed ‘Deepwave’ led by the United States National Centre for Atmospheric Research (NCAR) to study the phenomenon of westerly wind flows into the upper atmosphere.
During the study, NCAR will conduct 22 long zig-zag flights at high altitude across the Southern Alps using a Gulfstream-V aircraft and laser technology.
A special ground satellite has been set up in Hokitika, powerful enough to scan several hundred thousand feet into the atmosphere.
There will also be daily releases of specialised weather balloons from the airport throughout the study.
The project also involves the German space agency DLER, the University of Canterbury, National Institute of Water and Atmospheric Research (Niwa), and the Metservice.
Project scientist and group leader Bill Brown said the Hokitika part of the study would continue until early August.
Niwa had set up a base at Haast for the duration of the study.
Dr Brown said the westerly phenomenon itself was not the main focus, rather the energy it projects up into the “high atmosphere” as a result of the wind flow when it rose over the Southern Alps.
“The project is focusing on how that happens.”
The Southern Alps are one of two areas in the Southern Hemisphere where this wind effect — otherwise known as the Foehn effect — occurs most consistently. The other is in Patagonia, in South America.
This is partly due to the fast wave of air, otherwise known as the ‘jet stream’, which flows about 10km above the earth’s surface. It gains much greater upward momentum in the Southern Hemisphere, while the Northern Hemisphere jet stream is much less consistent due to the larger land mass covering the earth there.
“In the Southern Hemisphere, it means a lot more energy gets pushed up into the atmosphere. That’s not well modelled in forecast models at the moment,” Dr Brown said.
The main study interest for the United States is how the effect of that relates to long-term climate modelling, whereas the New Zealand interest is more around the subtle local weather effects.
“What we’re doing here is setting up a lot of equipment to monitor the winds coming on to the Coast and up into the mountains. The bulk of the work will be done in Christchurch.”
Dr Brown is a New Zealander who has been based in Colorado and working for NCAR for the past 16 years.