29 May 2015

Archives yield 'exciting' climate data find

7:41 am on 29 May 2015

A climate scientist in Central Otago has discovered weather pattern data taken 30 years ago, when ozone hole damage was just beginning to be understood.

Dan Smale on top of the NIWA's Lauder atmospheric research laboratory building kneeling behind a solar tracker that feeds light into a Fourier transform spectrometer used to measure atmospheric trace gases.

Dan Smale - on top of NIWA's atmospheric research laboratory building at Lauder, Central Otago Photo: NIWA / Dan Smale

A NIWA atmospheric technician, Dan Smale, stumbled across the 'mid-infra-red spectra' scientific readings taken on 29 May 1985.

He discovered them while archiving and updating historical archives at the institute's high country observatory at Lauder, where world-class atmospheric data is collected and analysed to add to knowledge about global climate change.

"Molecules in the atmosphere absorb sunlight. Each molecule, such as water vapour, ozone, carbon dioxide, methane, has a different absorption 'fingerprint' that is measurable," he said.

Infra-red spectra measurements are collected by an instrument called a Fourier transform interferometer and profile the sunlight-absorbing molecules in the atmosphere.

"By measuring these absorptions, we can say how much of a molecule is in the atmosphere: this is a well-established technique called spectroscopy."

Spectroscopic gas measurements can be made in the UV, visible and infrared wavelength regions.

Mr Smale said many gases of interest in the atmosphere absorb infra-red light, which is why scientists measure in the infra-red.

Tracking back to the 1980s

In the 1980s infra-red measurements revealed the gases responsible for destroying ozone and there was international concern over the discovery of a hole in the ozone layer.

Measurements made at Lauder and Scott Base by NIWA's predecessor, the Department of Scientific and Industrial Research, contributed to international research on the implications of the ozone hole.

Until this most recent find, NIWA had raw spectra data back to 1990 but the find of this additional data extends the spectra record back another five years.

"By repeatedly taking infra-red data over time and analysing it to measure gas amounts, we can see how gas amounts change over time," Mr Smale said.

"It's an exciting extension of climate science knowledge."

Ozone hole to greenhouse gases

Over the past three decades, there have been three major changes in atmospheric research.

Mr Smale said this included a change in focus, a greater multi-disciplinary approach to research and the use of technology.

The focus has shifted from ozone-hole research towards greenhouse gas and pollutant gas measurements.

The same instrumentation and analysis methodologies are used, and ozone and ozone-destroying substances are still measured, but more molecules are analysed.

There is now more collaborative work with atmospheric chemical modelers, which compare measurements to model simulations for a better understanding of how the atmosphere works. The measurements are also compared with increased numbers of satellite measurements.

But by far the biggest change is in the technology used.

Then and now: Old data stored on floppy disks 30 years ago adds to research material gathered by more modern techniques (1/2).

Then and now: Old data stored on floppy disks 30 years ago adds to research material gathered by more modern techniques. Photo: NIWA / Dan Smale

Then and now: Old data stored on floppy disks 30 years ago adds to research material gathered by more modern techniques (2/2).

Photo: NIWA / Dan Smale

While the fundamentals are the same, there has been a huge change in the amount of measurements, and the way they are collected.

Mr Smale said new instrumentation was more automated and had fewer faults.

In 1985, individual measurements were stored on a 180-kilobyte 5.25-inch floppy disk.

Now, all measurement data is stored on one terabyte hard drives.

"The instruments in 1985 collected only raw data, but now computers attached to the current instruments handle the data 1000 times faster."

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