Flight Campaign in Darwin Brought to a Successful Close

For the last time yesterday, the Russian high-altitude research aircraft Geophysica and the German Aerospace Centre’s (DLR) Falcon set off for tropical thunderclouds in Darwin (Australia). Over the last four weeks, the research aircraft undertook a total of nine joint measurement flights in the tropical atmosphere at the interface between the troposphere and stratosphere. Within the framework of the SCOUT-03 Project, they collected data which will be incorporated into the discussion on climate change, for instance at world climate conferences. The aircraft measurement campaign is part of the integrated EU project SCOUT-03 and was coordinated by Research Centre Jülich together with colleagues from the ETH Zürich (Swiss Federal Institute of Technology), Cambridge University and the DLR.

SCOUT-03 is analysing how the stratospheric ozone layer will change over the coming decades under conditions of global change. Scientists will thus be able to provide findings that will enable global assessments of ozone depletion and climate change to be made and incorporated into the Kyoto Protocol, for example. The Kyoto Protocol is currently being discussed at the World Climate Conference in the Canadian city of Montreal.

The measurement campaign in Australia focused on thunderclouds, which form almost daily at this time of year at altitudes of up to 20 kilometres at the “top end” of Australia. The tropics are of particular importance because this is where the exchange of air masses occurs between the lower (troposphere) and upper atmosphere (stratosphere). They are therefore the source region for many trace gases, such as chlorofluorocarbons, nitrogen oxides and water, which have a global influence on the ozone chemistry of the stratosphere. The gigantic thunderclouds on Darwin’s doorstep transport these air masses directly into the stratosphere within a short period of time.

In order to monitor the transport of tropospheric air masses up into the stratosphere, the pilots flew the research aircraft over or near to such thunderclouds five times. On 30 November, Geophysica and Falcon were even sent up into the atmosphere twice, with the additional support of two other research aircraft from the British project ACTIVE. “It is in itself a remarkable feat to have four research aircraft, packed full with measuring instruments, operate at various altitudes and different development stages of these thunderclouds within a specific timeframe”, explained Dr. Cornelius Schiller, coordinator of the SCOUT-03 aircraft campaign and physicist at Research Centre Jülich.
“This requires well-coordinated teamwork between the meteorologists, who deliver the weather forecasts to us, the teams of researchers, who operate the instruments, and finally the pilots, who appraise the measurement situation on site and accurately navigate the aircraft towards the object of scientific desire”, said Schiller of the difficulties involved. On top of this, changing weather conditions, for example, often require improvisation and spontaneous decisions. During further flights, the scientists investigated the large-scale dispersion of trace gasses and cirrus clouds.

“A first look at the data shows that the storms do indeed effectively transport water, nitrogen oxides and other trace gasses into the tropical tropopause region”, reported Schiller on the initial results. “They generate cirrus clouds at high altitudes, which were observed during most of the flights.” In the lower and middle atmosphere, Jülich scientists measured extremely low concentrations of water. “A more accurate analysis of the large data volume and a more detailed evaluation of the results will still take several months”, explained Prof. Martin Riese, Director at the Institute of Chemistry and Dynamics of the Geosphere at Research Centre Jülich. The first results will be discussed at an international SCOUT-03 conference at Research Centre Jülich from 20 – 24 March.

On Saturday, both aircraft will begin their return journey to Europe. They will cross the monsoon regions of Indonesia and Thailand, fly in the subtropics over India and Arabia and finally return to the mid-latitudes of Europe. Modern remote sensing methods play a central role in these global measurement flights. “The infrared telescope CRISTA-NF, recently modified at Jülich and the University of Wuppertal, will also measure the distribution according to altitude of a multitude of atmospheric trace gasses with a high spatial resolution during the return flight”, said Dr. Fred Stroh of Research Centre Jülich.