In a spectacular environmental campaign, as part of a big European project "SCOUT-O3" (1), around 120 scientists and engineers from 19 nations are currently observing trace gases and clouds in the atmosphere above Darwin in northern Australia. Five scientists from the Institute for Atmospheric and Climate Science at ETH Zurich (IACETH) are also taking part in the investigation. Under the guidance of Thomas Peter, Professor of Atmospheric Chemistry, they are accompanying two research planes through the thunderstorm known as Hector.

Transport into the stratosphere

The thunderstorm owes its name to the fact that in the weeks leading up to Australia's monsoon months (November/December) it appears, with great regularity, nearly every afternoon. Hector can shoot up to altitudes of up to 20 kilometres and therefore presents a gateway for the transport of air masses from the troposphere (0–17 km altitude) into the stratosphere (above 17 km).

Hector can transport gigantic quantities of air into the upper level of the troposphere. Scientists are now hoping to be able to quantify this vertical transport of air in a wide reaching series of experiments on a tropical storm system. They are also looking into which trace gases are pumped from here directly into the lower stratosphere, and therefore into the vital ozone layer.

Painstaking preparation

During the measuring campaign the Russian high-altitude research plane "Geophysica" and "Falcon", from the German Aviation and Space Centre, are flying through the thunderstorms. As these storms can develop an upward buoyancy of 40 metres a second and the danger of lightening striking a plane is high, this is a risky undertaking. It is therefore exceedingly important for the pilot that he can count on reliable flight preparations.

Preparations for a flight are based on meteorological forecasts, for which Dominik Brunner and Beiping Luo from IACETH are responsible. The scientists know how important their reports are. Stefan Fueglistaler, also from IACETH, accompanies the planes directly on the radar screen and transmits instructions to the pilots. This job calls for a high level of concentration because Geophysica streaks through Hector at altitudes of between 17 and 20 kilometres. Safety is the prime concern.

Ice cold and tropical heat

Working conditions in Darwin are anything other than easy. The tropical air outside has an average temperature of 38 degrees and relative humidity stands at 90 per cent. This makes every job harder to accomplish and it can play havoc with the sensitive measuring instruments. When the planes leave the minus 90 degree conditions of the the upper troposphere and come back to the hot humid air they drip like beer bottles taken out of the freezer and placed on the table in the garden on a hot summer's day. The temporal co-ordination of the flights co-ordinates, the rapid setting-up of instruments, the dressing of the Geophysica pilots in pressure suits and the daily consultations with the airport authorities are vital components if the mission is to succeed. A single mistake at any stage would mean cancellation of the flight–however good other preparations had been. Overall, the campaign needs the co-ordination of all of the 120 participants. Some of these work from the airport, others at the Charles Darwin University or at the National Bureau of Meteorology.

In a core team, and together with four colleagues from England, Germany and Italy, Thomas Peter co-ordinates and is responsible for the planning of the total 16 research flights, on location. It takes a huge amount of time and effort to prepare each flight, so it is no wonder that optimising each and every flight stands at a premium, and short term changes to the planning are possible. What is important for this is to be able to oversee the wide range of activities involved in the whole picture and to keep a cool head in a steamy situation. The experience of these scientists, combined with the almost daily occurrence of Hector and a little bit of luck with the meteorological flight conditions hold out hope that valuable scientific results can be provided with this project.