New cloud research project launched at the German Antarctic station Neumayer-III

Leipzig/Bremerhaven. Over the next 12 months, the vertical distribution of aerosol particles and clouds in the atmosphere above the German Neumayer III station of the Alfred Wegener Institute (AWI) will be observed from the ground for the first time. These profile measurements are the first of their kind in Queen Maud Land on the Atlantic sector of Antarctica and thus in an area larger than Greenland. The measuring platform OCEANET-Atmosphere of the Leibniz Institute for Tropospheric Research (TROPOS), which was already on the way for a whole year in the Arctic during the international MOSAiC expedition on the AWI research icebreaker Polarstern will now be operated in the Antarctic until 2024.

The unique set of laser and radar instruments was installed at Neumayer III in early 2023. The project COALA (Continuous Observations of Aerosol-Cloud Interactions in Antarctica) is funded by the German Research Foundation (DFG) and is carried out in close cooperation with the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI).

The Antarctic continent as the largest fresh-water reservoir on our planet and the surrounding Southern Ocean are key regions in the changing global climate system. However, weather and climate models have not yet succeeded in satisfactorily representing processes such as cloud cover, precipitation, and the radiation budget in this region. These uncertainties lead to factors such as ocean-surface temperature, energy exchange between ocean and atmosphere, or snow amounts being incorrectly estimated. Scientists lack data on cloud formation in the clean atmosphere of this relatively uninhabited region. In this context, “clean” refers to the fact that aerosol particles, i.e. the smallest airborne particles such as sea salt, desert dust, pollution, or smoke, only occur in very small quantities. A special challenge for the researchers is the unusually high proportion of supercooled water droplets in the clouds over Antarctica. Liquid cloud water only appears at temperatures between  -38 °C and 0 °C if ice nuclei - a particular subspecies of atmospheric aerosol particles required for droplet freezing - are missing. Therefore, aerosol particles and the associated ice-formation processes are a major focus in current cloud research.

In contrast to the Northern Hemisphere with more land masses and a correspondingly higher population, there are comparatively few sources of aerosol particles around Antarctica. Long-distance transport, which has little been investigated so far, could therefore play an important role. The fact that the smoke from the Siberian wildfires in summer 2019 continued to persist over the central Arctic the following winter was an unexpected result of the MOSAiC expedition. "Thanks to our measurements, it became clear that these particles can affect the atmosphere in the Polar Regions for a very long time. In the southern hemisphere, we were able to detect the smoke from the large Australian wildfires in 2019/20 even on the other side of the Pacific in Chile. But how much of this smoke or of other aerosol particles reach Antarctica? At the moment, no one can say that. We hope that we can close this knowledge gap with the measurements at Neumayer III," explains Dr Patric Seifert from TROPOS.

Aircraft measurements are rare at the poles and can ever only be a snapshot. Also, these small-scale aerosol-cloud interaction processes cannot be recorded properly from satellites. Ground-based, vertically resolved long-term observations of aerosol, clouds and precipitation in Antarctica are also scarce. "According to our research, there have only been 13 months of coordinated and continuous measurements with cloud radar and aerosol lidar in the vast Antarctic, and only on the other side of Antarctica - in the section of Antarctica that is 3500 km away and adjacent to the Pacific Ocean. In contrast to Neumayer III, the US station McMurdo stands on rock instead of on an ice shelf, which also makes a big difference," emphasises Dr Ronny Engelmann from TROPOS, who is in charge of the measuring platform OCEANET-Atmosphere and who was also part of the international MOSAiC expedition in the Arctic. The platform is an autonomous, polar-tested, modified 20-foot container full of modern atmospheric measurement equipment. At the moment, it is the only polar single-container platform that can observe aerosols, clouds and precipitation with multi-wave lidar, radar, and microwave radiometer, and turbulent air movements in clouds with Doppler lidar and radar.

Within the DFG research project COALA, the container has been transported to Antarctica on the German research icebreaker Polarstern and was installed on a solid container platform next to the Neumayer III research station which is located on the Ekström Ice Shelf around 4000 km south of Cape Town. OCEANET-Atmosphere is literally following in the footsteps, of the international EDEN-ISS project, which operated a container system with greenhouse experiments for catering in space at this exact location since 2018. Early 2023, the two TROPOS researchers Ronny Engelmann and Martin Radenz put their measurement equipment into operation. Meanwhile, the green laser beam of the multiwavelength lidar scans the atmosphere above Neumayer III for the first time. A lidar sometimes also referred to as "light radar" sends short laser pulses from the ground into the atmosphere and picks up the backscattered light by a special receiver. From the transit time, intensity and polarisation of the return signal, information about the height, quantity and type of dust particles in the atmosphere can be derived. Ronny Engelmann is already back home after the setup. His colleague Martin Radenz, on the other hand, will remain on the ice: "To ensure the quality of the measurements outside the very short summer season and to map the entire annual cycle, there are hardly any alternatives but to stay on site. The station is simply too isolated for a regular exchange of personnel in winter, as was the case with MOSAiC. A challenge for which we have been well-prepared thanks to the experience of the AWI," reports Dr Martin Radenz, who is part of the 10-member team that will spend the winter at Neumayer Station III in 2023.

Since December 2019, two parameters that provide information about cloud formation are already measured at the trace-substance observatory of Neumayer Station III with support from Leipzig: the concentrations of cloud condensation nuclei and ice nucleation particles. These continuous measurements allow conclusions about the seasonal changes in cloud cover. "We see a pronounced annual cycle with values of cloud condensation nuclei that are higher by a factor of ten in summer," says Dr Silvia Henning from TROPOS, who is in charge of these measurements in cooperation with AWI. “Together with the new remote-sensing measurements, we will create a comprehensive data set that characterises aerosol-cloud interactions from the ground up to the stratosphere. With help of the OCEANET-Atmosphere instruments, we are raising the possibilities of cloud research to a new level" emphasises Martin Radenz, referring to the capabilities of Doppler lidar and Doppler radar to observe air movements in the atmosphere. "So far, only a few studies have paid attention to the fact that atmospheric turbulence can also have an important influence on the formation of clouds and on the formation of water droplets at temperatures below 0 °C. Vertical winds are another indispensable element to be able to properly describe the transformation of aerosol particles and water vapour into clouds, and to predict ice formation and precipitation."

As part of the DFG Transregio "Arctic Climate Warming", TROPOS has been investigating clouds in the Arctic together with Leipzig University since 2016. In addition, the processes in the southern hemisphere have also come into focus in recent years: in 2016/17, cloud researchers from Leipzig were part of the international Antarctic circumnavigation ACE. In 2018-2021, extensive measurements took place in southern Chile and a larger measurement campaign is currently planned for 2025 in New Zealand. The new project at the German Antarctic station is another milestone for this research: "The fact that a measurement system winters in both the Arctic and the Antarctic is an international novelty and a great opportunity for us to find out more about the differences between the relatively polluted Northern Hemisphere and the relatively clean Southern Hemisphere. This work was made possible, above all, by the many years of cooperation with the Alfred Wegner Institute and by the funding from the federal and state governments and the German Research Foundation, to whom we owe our thanks," explains Prof Andreas Macke, Director of TROPOS. The measurements that now started at Neumayer Station III will later be compared with existing data sets from southern Chile, Cyprus, Germany and the Arctic and provide new insights into why clouds in the far south differ so much from those in the northern hemisphere. Tilo Arnhold

Further information and links:

Latest lidar data from Antarctica:
Polly Arielle @ AWI antarctic station Neumayer III
https://polly.tropos.de/calendar/location/49?&individual_page=2023

blog:
COALA 2022 – 2023
https://www.tropos.de/en/current-issues/campaigns/blogs-and-reports/coala-2022-2023

TROPOS press releases on Antarctica & Arctic:

German researchers in New Zealand on the traces of climate change (18 Nov 2022)
https://www.tropos.de/en/current-issues/press-releases/details/deutsche-forschende-in-neuseeland-auf-den-spuren-der-klimaveraenderung
Updrafts crucial - clouds in the southern hemisphere more precisely understood (26 Jan 2022)
https://www.tropos.de/en/current-issues/press-releases/details/aufwinde-entscheidend-wolken-in-der-suedhemisphaere-genauer-verstanden
Climate change and wildfires could increase ozone hole (21 Jan 2022)
https://www.tropos.de/en/current-issues/press-releases/details/klimawandel-und-waldbraende-koennten-ozonloch-vergroessern
Unique view into the "new Arctic": International MOSAiC expedition successfully completed (12 Oct 2020)
https://www.tropos.de/en/current-issues/press-releases/details/einmaliger-blick-in-die-neue-arktis-internationale-mosaic-expedition-erfolgreich-beendet
Around the South Pole in 90 days (16 Dec 2016)
https://www.tropos.de/aktuelles/pressemitteilungen/details/in-90-tagen-um-den-suedpol  

Neumayer Station III in the Antarctic

Neumayer Station III
https://www.awi.de/en/expedition/stations/neumayer-station-iii.html
Neumayer Station III - The Meteorological Observatory
https://www.awi.de/en/science/long-term-observations/atmosphere/antarctic-neumayer/meteorology.html
Neumayer Station III - The Trace Material Observatory ("Spuso")
https://www.awi.de/en/science/long-term-observations/atmosphere/antarctic-neumayer/air-chemistry.html
Antarctic Blog: AtkaXpress
https://blogs.helmholtz.de/atkaxpress/en/

Funding:

DFG project COALA (Continuous Observations of Aerosol-Cloud Interaction in Antarctica).
https://gepris.dfg.de/gepris/projekt/463307613?language=en
DFG project VACCINE+ (Variation of Antarctic cloud condensation nucleus (CCN) and ice nucleus (INP) concentrations and properties at Neumayer III compared to their values in the Arctic at the Villum research station (VACCINE+))
https://gepris.dfg.de/gepris/projekt/442925270?language=en