A high-altitude balloon being launched near Beaufort West by Thumeka Mkololo, Pieter Labuschagne (both from the South African Weather Service) and Kiriyaki Blazaki (German Research Centre Juelich)
On a farm close to Beaufort West in the Karoo, Dr Markus Geldenhuys and a team of South African and German scientists have spent the past two weeks launching six huge, white weather balloons.
In a first-of-its-kind project for Africa, these high-altitude balloons were released to measure pollutants and greenhouse gases in the atmosphere to help improve long-term weather forecasts and projections of climate change, among other things. The project is a collaboration between the South African Weather Service and the German Research Centre Juelich.
The balloons can carry small measuring instruments to an altitude of nearly 35km, well above the range of aircraft, to investigate the atmosphere from the ground up to those otherwise inaccessible altitudes, according to the weather service.
Normally, it said, scientists have to rely on remote sensing instruments, such as satellites, but even this sophisticated equipment requires independent verification, which is one of the project’s objectives. “The gases in question are of importance as they can absorb sun energy at these high altitudes, which influences surface weather.”
Scarce data
Data about important pollutants and greenhouse gases in the atmosphere is extremely scarce in the Southern Hemisphere, especially at higher altitudes.
“One of the reasons is because there’s not a lot of instruments that can go this high, so these balloons are the only instruments that can measure accurate high-resolution observations at these altitudes,” Geldenhuys, a forecaster at the weather service, told the Mail & Guardian.
“The second reason is that there’s not so many countries in the Southern Hemisphere that do this. This is the first time that some of these measurements are taking place in the Southern Hemisphere.”
The Karoo is the ideal location for the project. “We need to recover our instruments after the balloon bursts, and of course if we do it close to the coast, it will end up in the ocean and if we do it close to mountains, it will land in inaccessible areas. The Karoo provided a nice and flat place to do these experiments and to allow an easier recovery.”
‘Needle-and-haystack scenario’
The balloons, he said, stayed up for about two hours and took about 30 minutes to fall back to earth. The highest reached an altitude of 33.5km.
The measuring instruments used are tiny compared to satellites, but are big compared to normal weather balloons, which weigh less than 200g. “This payload, of what instruments we sent up, was sometimes up to 4kg. So, this is quite a bit larger than the normal weather balloons but quite a bit smaller than satellites and aircraft.”
The challenges are multifold, said the weather service. “Just imagine filling a latex balloon with enough helium to lift a 4kg instrument with a GPS tracker. This balloon ascends to an altitude of 35km, while recording temperature, pressure, water content, methane, carbon dioxide, ozone etc, during the flight.”
After bursting they predict where the parachute will drift to, find out on which farm it has landed and try to locate it on the farm, which is “very much a needle-in-a-haystack scenario”.
Obstacles included sudden wind gusts breaking a balloon before it can even take off and recovering the sensors after a particularly hard landing — which is time-critical — during a thunderstorm.
The launches have already provided valuable, precise information on the vertical distribution of the concentrations of water vapour, ozone, carbon dioxide, carbon monoxide, methane and many other trace gases (gases in the atmosphere which have a small concentration with respect to oxygen and nitrogen), it said.
Furthering understanding
“Some of the benefits of this collaboration include to further our understanding of atmospheric processes, to improve satellite products by providing an independent point of comparison and, in the longer term, to help improve long-term weather forecasts as well as projections of future climate change.”
The plan is to continue the project in the future, Geldenhuys said. “We will now take a break of one year and next year the plan is to come back and to re-measure everything so that we have the dataset over two different years to compare with.”
Most of the project’s work was funded by the Germans, he added. “Generally, the balloon launches are not that expensive because we’re recovering the instruments afterwards and then we can reuse them. That’s the nice thing about balloon experiments. The only things that we lose are the helium gas and then the balloon itself, which bursts, but the rest we can all reuse.”
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