Outreach |

Hannah Kessenich busts ozone hole myths

Wed, 16 Sep 2026 00:00:00 +1200

The University of Otago marked World Ozone Day by asking Hannah Kessenich to take apart some common myths about the ozone hole. She dispatched three of them in a single sentence.

Three facts that would surprise most New Zealanders

The hole is not above us. It sits over Antarctica and the surrounding ocean. Its edge grazes New Zealand occasionally, maybe one or two days a year, and that is all.

It is not open year-round. It opens for roughly three months each spring, inside the polar vortex, and closes again.

It is not why we burn. New Zealanders face high UV because the Earth’s orbit brings the Southern Hemisphere slightly closer to the sun in our summer, and because our air is unusually clean. Both would be true with no ozone hole at all.

A fourth, less comfortable point: the hole is mostly a natural phenomenon. Stratospheric winds and extreme cold over the pole account for the majority of it. Humans supplied the final ingredient by emitting chlorofluorocarbons, causing the hole to open.

Why this is Tuwhiri’s problem too

The interview ends on something that will be familiar to anyone following this programme. Asked about her research plans, Hannah mentions a paper in review proposing a way to classify ozone hole severity — closely related to the in May — and then mentions, almost in passing, that she is helping build a new instrument meant to take over from a NASA satellite.

That project is Tuwhiri.

Two of her observations explain why the instrument matters. The ozone hole has been lasting longer in recent years than in any previous decade, and nobody yet knows whether that is a signature of climate change. And current projections have it continuing to open until around 2090 — projections which, she notes, do not fully reproduce what is already being observed.

Both are questions you can only answer by continuing to observe the atmosphere. Aura’s Microwave Limb Sounder, the instrument that has watched the Antarctic stratosphere through the polar winter for two decades, will run out of fuel with no replacement planned. Tuwhiri exists to build one small and cheap enough that a country of New Zealand’s size can afford to fly it.

The other reason the hole matters

While the hole is open it creates a pocket of cold air over the South Pole that shifts circulation bands across the whole Southern Hemisphere — changing where winds strike New Zealand, how much rain they carry, and whether a summer brings drought or fire.

Hannah points to the October winds that brought trees down on the Otago campus in 2025. This was in part the work of cold air being pushed north following an ozone hole destabilizing event.

How she got here

Hannah came to Otago from the United States following a physics degree and a job in the technology sector. I thought the ozone hole was old news and a solved problem. It turns out to have many unanswered questions., she says of the field. She went on to join under Annika Seppälä, who now leads Tuwhiri’s atmospheric science. Those unanswered questions became her PhD. She completed it last year and is now a postdoctoral fellow in the Department of Physics.

Minister Penny Simmonds visits the photonics laboratory

Tue, 11 Aug 2026 00:00:00 +1200

Hon Penny Simmonds, Minister of Science, Innovation and Technology and Minister for Tertiary Education, visited the Tuwhiri photonics laboratory at the University of Otago on 11 August 2026.

The visit follows one by her predecessor, Dr Shane Reti, in December 2025, which means both ministers holding the science portfolio during the programme’s first year have now seen the instrument development first hand.

The timing was useful. The programme’s kick-off meeting three weeks earlier had brought the atmospheric science, photonics and engineering teams together to settle what the instrument must achieve, so there was a clearer story to tell than there would have been in the first months of the programme.

Otago Daily Times: clock ticking on bid to replace important weather satellite

Tue, 21 Jul 2026 00:00:00 +1200

The Otago Daily Times reported on Tuwhiri during the programme’s kick-off meeting, under the headline Clock ticking on bid to replace important weather satellite.

The headline gets the problem right. NASA’s Aura satellite has been measuring ozone and related gases for more than two decades, and its Microwave Limb Sounder is the only instrument capable of watching the Antarctic stratosphere through the polar winter, when the ozone hole forms. Aura will run out of fuel, and no replacement mission is planned — conventional instruments of that kind cost more than anyone is currently willing to spend.

The meeting the article covers, held at the University of Otago from 19 to 21 July 2026, brought the whole programme team together for the first time and was the occasion on which the name Tuwhiri was presented publicly.

Coverage in the regional paper matters more than its circulation suggests. Much of what Tuwhiri is building will be made and flown in New Zealand, and the case for public investment is easier to make when people can read about it somewhere other than a university press release.

Minister Shane Reti visits the photonics laboratory

Wed, 10 Dec 2025 00:00:00 +1300

Dr Shane Reti, then Minister of Science, Innovation and Technology, visited the photonics laboratory at the University of Otago in December 2025.

The visit was a chance to show, rather than describe, what the programme is building: the whispering-gallery-mode resonators at the heart of the instrument, and the up-conversion experiment that turns faint microwave and terahertz signals from the atmosphere into optical light a compact detector can measure.

The argument Tuwhiri makes is partly an economic one — that an instrument small and cheap enough to fly on a CubeSat changes what a country of New Zealand’s size can afford to monitor from space. That case is easier to make standing next to the apparatus.

Tuwhiri Programme Kick-off Meeting

Mon, 01 Jan 0001 00:00:00 +0000

The occasion

Everyone in the programme in one place for the first time: three research areas, the advisory board, industry partners, and colleagues from Adelaide, Caltech, Earth Sciences New Zealand, Waikato, AUT and the Paihau–Robinson Research Institute.

The welcome function opened with a mihi whakatau, followed by a welcome from Programme Lead Professor Harald Schwefel. Jessa Barder then presented the programme’s new name — Tuwhiri, from the Māori word meaning a clue, or means of discovering something hidden, which is an appropriate metaphor for what an atmospheric sounder does, as well as to reveal or make known, which is an accurate description of the programme’s goals.

Sunday 19 July — Welcome function

Terrace Lounge, University Union Building.

Mihi whakatau, the welcome from the Programme Lead, the presentation of the programme name, and guided tours of the research laboratories.

Monday 20 July — Setting out the problem

Walsh Building.

The morning established why the work matters and where each area currently stands. Annika Seppälä opened on the case for space-based climate and atmosphere monitoring. Mallika Suresh followed on dielectric resonators for nonlinear optical upconversion of microwave signals, and Randy Pollock set out the engineering team’s staffing, status and open questions.

The second session widened the frame: Peter Gibson on climate change projections for New Zealand from CMIP6, Andrey Matsko on microphotonics for spaceborne timing and remote sensing, and Withawat Withayachumnankul on terahertz technology from devices through to sensing and communications.

The afternoon split in two. One workshop took on sensor, platform and data systems integration, chaired by Betina Pavri and Mallika Suresh; the other planned the atmospheric science model simulations, chaired by Annika Seppälä.

The day closed with Jessa Barder on plans for community engagement, a contribution from Richard Querel, and open discussion.

Tuesday 21 July — From requirements to instrument

Centre for Innovation and Mellor Laboratories.

The morning ran from the science down to the hardware. Hamish Lewis presented late-century projections of climate extremes across New Zealand; Florian Sedlmeir on millimetre-wave atmospheric radiometry via nonlinear optical upconversion; Hannah Kessenich on a new diagnostic metric for quantifying Antarctic ozone hole dynamics; John Cater on thermal and mission design; and Betina Pavri on Kea Mk1 interface requirements and environmental test planning.

Two further workshops ran in parallel. The first brought the atmospheric and engineering teams together on instrument requirements for science, chaired by Randy Pollock — the conversation that decides what the instrument has to achieve. The second, chaired by Greg Bodeker, addressed uptake and impact.

A poster session ran over lunch, and Harald Schwefel closed the meeting.