October 26, 2021

EOC gives Infrared Spectrometer Training to AWI Staff Overwintering at Neumayer

Since 2013 the Earth Observation Center has jointly operated an Antarctic measurement station together with the Alfred Wegener Institute (AWI) to record the temperature of the atmosphere at 90 kilometres altitude. In order to extend this valuable series of local measurements also under the most hostile environmental conditions, an overwintering AWI staff member is once again being trained in the use of a DLR instrument.

The altitude region being monitored is important for understanding anthropogenic climate change. While the greenhouse effect gives rise to higher temperatures at ground level, climate models show that they sink in the upper mesosphere. The reason is CO2. Like a rescue foil it prevents heat loss to space, increasing the temperature on one side and decreasing it on the other. Because of the low density of the atmosphere in the mesosphere it can be expected that temperatures at 90 km altitude will drop in the long term because of the increase in CO2 concentration, falling as much as ten times faster than they increase at ground level. Because of this amplifier effect climate signals could possibly be recognized especially well in the mesosphere. The polar regions are particularly interesting because they already show the largest temperature changes at ground level.

Temperature measurements at the boundary layer between the atmosphere and space are made with a spectrometer. This instrument is capable of detecting at night the very weak glow that develops at 90 kilometres altitude. This is where hydroxyl molecules (OH), a compound made of atomic oxygen and atomic hydrogen, emit infrared radiation, which is invisible to the human eye. Researchers can read the wavelength structure in the range of ca. 1.5 micrometres like a fingerprint and thereby draw conclusions about the temperature.

In order to distinguish long-term climate change from short-term chaotic activity in the atmosphere, long-term monitoring is essential. The success of these measurements is therefore based not least on good collaboration with the Alfred Wegener Institute (AWI). This makes it possible for all the science instruments to be tended by highly-qualified scientists also during Antarctic winter when the station is isolated from the outside world for months at a time. The overwintering staff is exchanged annually and receive special training for each of the instruments in their particular area of responsibility before they set off for the Antarctic. This week it was that time again: Hannes Keck visited EOC in Oberpfaffenhofen to receive in-depth training in the GRIPS Instrument (GRound Based Infrared P-Branch Spectrometer) (figure 3). These instruments are developed, and if necessary serviced, at EOC in Oberpfaffenhofen, so for training purposes there is an opportunity to take apart and then reintegrated a structurally comparable instrument.

Every year there is the hope that taking this spectrometer apart remains a one-time affair, because an operational instrument should of course, function on its own to the extent possible. But this year the instrument training turned out to be especially worthwhile. In mid-August the most violent storm ever experienced at Neumayer Station swept over the facility with peak velocities up to 148 km/h (and gusts up to 204 km/h). This resulted in some damage, including a power failure that lasted several days in the lab area, so that all the instruments were then more or less directly subjected to the Antarctic climate. At -15°C GRIPS was however “only lightly powdered with snow” and so last year it was possible for the trained AWI staff member to put GRIPS into operation again as soon as the lab had been repaired.

Thanks to the commitment of AWI colleagues, each year data of uniform quality is available to science, including also this year with its occasional harsh constraints, even when the servicing is much more difficult since the limited lab space has to be used as efficiently as possible (figure 4).