A European research project led by ETH Zurich has used fixed-wing drones to take measurements on aerosols from inside clouds containing ice.
Part of BACCHUS, an EU-funded collaboration exploring the impact of clouds on climate change, it marks the first time drones have been used for this type of vertical profiling. The amount of ice contained within clouds influences the levels of precipitation they can discharge, as well as the amount of radiation between the Sun and the Earth. Natural aerosols such as dust as pollen can play a role in this ice formation in clouds, as can man-made aerosols. Part of the project was to determine the proportion of each.
“We investigated the importance of biogenic (natural or pre-industrial) versus anthropogenic (human-made) emissions for aerosol-cloud interactions in regions that are key regulators of the Earth’s climate, such as the Amazon rainforest or the Arctic,” said project coordinator Professor Ulrike Lohmann, a climate scientist at ETH Zurich.
“Very little data is available for many of these regions, particularly over oceans. To start with we wanted to know what fraction of the cloud is composed of water droplets versus ice crystals and then how this was affected by aerosols.”
BACCHUS has been running since 2013 and in that time has relied on and data from the ground, research vessels and large research aircraft, as well as satellite remote-sensing measurements. By employing drones, however, the scientists have been able to harvest a richer set of data that more closely reflects the reality of ice cloud formation. Equipped with lightweight, commercially available sensors for temperature, humidity and aerosol particulates, the drones provided an even better picture than conventional aircraft.
“You get only a few measurement points using aircraft,” said Professor Lohmann. “Drones are light and highly flexible. They can also facilitate more frequent cloud measurements in different locations around the world, particularly remote regions where data is missing.”
The drones were first deployed in the dust-laden air above a remote part of Cyprus. Data from the missions was fed into a unique database on ice clouds, bringing together long-term observations and field data on cloud microphysical properties and ice-nucleating particles. This new drone data will form part of the wider BACCHUS database, which includes analysis of Greenland ice cores and atmospheric measurements from a circumnavigation of Antarctica.
“We were able to get many measurements of ice-nucleating particles in a previously under-sampled area of the Southern Ocean,” said Lohmann. “We also wanted to see how important future Arctic ship traffic could be for clouds and how much ship pollution matters in such a pristine environment.”