How does the atmosphere’s washing machine work?

Media releases, Merck

A German aircraft flying out of Cairns is measuring the chemistry of the clouds above Australia and the Pacific.

FEBRUARY 23, 2024: This week, a German research aircraft is sampling air up to 15 km above Australia and the Pacific Ocean. The CAFE-Pacific Mission aims to better understand:

  • how the tropical atmosphere deals with air pollution;
  • how clouds form over oceans;
  • how to refine weather and climate models, leading to better forecasts and projections; and, fundamentally
  • to better understand the chemistry of climate.

Flying out of Cairns in the northeast of Australia, the Chemistry of the Atmosphere: Field Experiment (CAFE) team are tracking weather events and taking atmospheric measurements to better understand the atmospheric chemistry occurring above the clouds.

The HALO research aircraft, a modified G550.

This is their third mission, using a highly modified Gulfstream G550 ultra long-range jet capable of exploring the full extent of the troposphere from the ground up to about 15 km above sea level.

Described by some researchers as the atmosphere’s washing machine, weather events in the tropics play a crucial role in clearing gases and particulates emitted from both natural and human-induced sources.

“In past missions, we have collected data under pristine conditions above the Amazon and in regions in Africa where biomass is burned, and where dust and pollutants are released into the atmosphere. We will compare these results with the data we now measure over the Pacific Ocean,” explains Professor Jos Lelieveld, Director of the Atmospheric Chemistry Department at the Max Planck Institute for Chemistry, and Principle Investigator of the CAFE-Pacific research project.

The area offshore from Australia’s northeast is of particular interest to the team as the high temperature of the ocean there causes the strongest high-reaching convection in the world. These columns of upward-rising warm air act as highways for heat, moisture, particulates, and gasses to be transported from the surface of the planet high into the atmosphere.

“The combination of intense solar radiation, mixing due to convection, large regional differences in lightning activity, and contrasting tropical waters and the Australian continent means there’s everything you need for a lot of interesting atmospheric chemistry to occur,” says Dr Clara Nussbaumer, a postdoctoral researcher working on the mission from the Max Planck Institute for Chemistry.

“It’s an exciting place to explore as an atmospheric scientist.”
Each flight lasts up to 9 hours, with four of the research team work monitoring and controlling the 15 different scientific instruments on board, maintaining contact with colleagues on the ground, and guiding the pilots to any last-minute opportunistic requests to change the flight plan.

“When we have a prediction that a weather event will happen, we can design a flight path to go check if what we expected actually occurs,” says Professor Joachim Curtius, Professor at the Institute for Atmosphere and Environment, Goethe University Frankfurt. Prof. Curtius is the co-Principal Investigator of the mission.

“Of course, it’s great when we find things where we expect them—it means our models are reliable—but it’s probably more exciting to find things that we don’t quite expect as it gives us the chance to further improve the forecasts and predictions under our changing climate.”

Scientific instruments on the HALO research aircraft.

The unique research aircraft has been equipped with highly sensitive instruments normally only found in well-equipped chemistry labs. Like the aircraft itself, many of these instruments have been modified or even custom built to achieve the sensitivity, accuracy and reliability required to perform in the trying environment of an aircraft in the tropics.

“We are often measuring trace gases in the atmosphere at levels as low as one part per trillion. Imagine this as around one drop in twenty Olympic-sized swimming pools,” adds Dr Nussbaumer.

“And we have to do this extremely fast because we’re flying in an aircraft at around 250 metres per second. It is normal for the instrument I take care of to measure 10 data points in a single second.”
By the end of February, the science team will have completed a total of around 150 flight hours, collecting measurements in areas that have never before been sampled.

“All the CAFE measurements will help us improve the computer models of the chemical processes in the atmosphere. This will help us even more accurately predict future climate developments,” says Prof. Curtius.

The CAFE-Pacific mission is coordinated by the Max Planck Institute for Chemistry and Goethe University Frankfurt and will conclude at the end of February.

The research has captured the attention of Ms Rebecca Lee, Managing Director of Merck Life Science, Country Speaker Merck Group ANZ, and Chair of the Advisory Council of the German-Australian Chamber of Industry and Commerce. Merck ANZ facilitated the mission locally by providing the chemicals required for calibrating the instruments on the aircraft.

“This fundamental research being carried out by the Max Planck Institute for Chemistry with several scientific partners from Germany is essential to our understanding of atmospheric science,” she says.
“It is crucial for open international collaboration to continue for the good of our collective knowledge, environment, and humanity at large. Australia has much to share with the rest of the world, and there is also so much we can learn from our colleagues overseas.”

A media pack including audio quotes from researchers, images and video of the aircraft is available.

Audio files and transcripts of interviews: click here.
Photos and videos: click here.
Whole shared media pack: click here.
TV Media B-Roll: click here.

Very limited interview opportunities are available, and may be in German time-zones. Contact:

Tom Carruthers
+61 404 404 026

About the HALO aircraft

HALO is based on a Gulfstream G550 ultra long-range jet aircraft. The combination of range, cruising altitude, payload and comprehensive instrumentation make the aircraft a globally unique research platform.

The High Altitude and Long Range (HALO) research aircraft is a joint initiative by German environment and climate research bodies. HALO is funded by contributions from the Federal Ministry of Education and Research (Bundesministerium für Bildung und Forschung; BMBF), the German Research Foundation (Deutsche Forschungsgemeinschaft; DFG), the Helmholtz Association of German Research Centers (Helmholtz-Gemeinschaft Deutscher Forschungszentren), the Max Planck Society (Max-Planck-Gesellschaft; MPG), the Leibniz Association (Leibniz-Gemeinschaft), the Free State of Bavaria (Freistaat Bayern), the Karlsruhe Institute of Technology (KIT), Forschungszentrum Jülich and the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). DLR is both the owner and operator of the aircraft.

About the Max Planck Institute for Chemistry

The Max Planck Institute for Chemistry (MPIC) is one of the two oldest institutes of the Max Planck Society. It was founded in 1912 as the Kaiser Wilhelm Institute for Chemistry in Berlin, and it was relocated to Mainz in 1949. Particularly well-known scientists in the Institute´s history are the Nobel laureates Richard Willstätter, Otto Hahn, and Paul Crutzen.

Currently the institute employs some 350 staff in four departments (Atmospheric Chemistry, Climate Geochemistry, Multiphase Chemistry, and Particle Chemistry) and additional research groups. Current research at the Max Planck Institute for Chemistry in Mainz aims at an integral understanding of chemical processes in the Earth system, particularly in the atmosphere and biosphere. Investigations address a wide range of interactions between air, water, soil, life and climate in the course of Earth history up to today´s human-driven epoch, the Anthropocene.

About Goethe University Frankfurt

With its research strength and international orientation, Goethe University is one of Frankfurt’s largest employers and a member of the association of the 15 major research-intensive and leading medical universities in Germany (German U15). Together with the Technical University of Darmstadt and Johannes Gutenberg University Mainz, Goethe University Frankfurt operates the strategic Rhine-Main Universities alliance (RMU). Established in 1914 as a foundation university with funding from Frankfurt’s citizens, Goethe University enjoys a high degree of autonomy, and is embedded in a highly participatory and supportive environment.

Research at Goethe University is structured into six profile areas spanning the humanities, social sciences, economics, natural and life sciences, as well as medicine – and is conducted in an interdisciplinary, cross-faculty and self-governed manner. Whether it concerns teaching and research, or the transfer of technology and knowledge in close interaction with civil society, Goethe University delivers contributions to meet the challenges of the 21st century and acts as a driving force for the progressive development of society, politics, and business – together with its regional, national, and international partners. Based on its holistically conceived, research-oriented educational process, Goethe University is dedicated to qualifying its students to become responsible, cosmopolitan citizens.