M.A. Linda Münnig
13. Dec. 2017 (10:15) 
Measurement campaign in the Arctic with KIT researchers in the Pallas Cloud Experiment

“Why does it rain or snow from a cloud, and why does it not just fall out of the sky as a whole?” Questions like this are what motivate physicist Dr. Ottmar Möhler, who works at the Karlsruhe Institute of Technology (KIT) in the Institute of Meteorology and Climate Research in the department Atmospheric Aerosol Research. Here, Dr. Möhler heads the group “Aerosol Cloud Processes.” Clouds play a major role in shaping weather patterns, and research in this specialist field is of paramount importance in relation to climate research.


The research station of the Finnish Meteorological Institute in the Pallas National Park in the Arctic

Photo: Dr. Ottmar Möhler

In September, Dr. Möhler was able to take part in the measurement campaign as part of the 7th Pallas Cloud Experiment in the Arctic, together with Palas® Managing Director Dr.-Ing. Maximilian Weiß and Gerd Schaufelberger, Managing Director of Airclip GmbH. The main focus of this measurement campaign in the
north of Finland was on vertical profiling of clouds with unmanned aircraft and drones and ground measurements at the research station operated by the Finnish Meteorological Institute (FMI), the Finnish counterpart to the German Meteorological Service (Deutscher Wetterdienst, DWD), in the Pallas-Yllästunturi National Park. Teams of researchers from Finland, Cyprus, UK and Germany carried out measurements with balloons, fixed-wing unmanned aircraft and flying drones in the different cloud layers. The HORUS multicopter from Airclip with the Fidas® Fly 100 aerosol spectrometer from Palas® was used to collect data on the size distribution and number concentration of particles under, in and above the clouds. At the same time, measurement data was also collected with another Fidas® Fly at the research station. The Pallas Cloud Experiment, which Palas® took part in under its own initiative, forms part of the European ACTRIS-2 research project, in which data is collected from research stations all around Europe on transient reactive trace gases, aerosols and clouds and made available for research.

2017-09_Finland_IMG_4153_Möhler_Weiss.jpg Dr.-Ing. Maximilian Weiß and Dr. Ottmar Möhler out and about at the research station in Finland

Photo: Dr. Ottmar Möhler

“During the fall and winter months, so-called Arctic Layer Clouds form there. These are layers Fidas® Fly collects data for cloud research Measurement campaign in the Arctic with KIT researchers in the Pallas Cloud Experiment of cloud formed of liquid droplets that lie very low,” explains Dr. Möhler as he talks about the special conditions at the research station in Finland. “Once the sun no longer shines quite as
strongly, the convection currents from below are reduced, because of which the so-called planetary boundary layer is formed at a lower altitude.” In Central Europe, this boundary layer forms at an altitude of around two kilometers, but it is less than one kilometer in the north of Finland, so this part of the world offers particularly good conditions for the measurements. “In some cases, the cloud base is also lower,” adds Dr. Möhler, “so that the station, which is not really all that high up, often finds itself in the clouds.”

Focusing on ice-forming particles

The cloud researchers are particularly interested in ice-nucleating particles that contribute to the formation of ice in these clouds. They form a very small subset of the aerosols that are measured overall with Fidas® and are particularly relevant for the development of precipitation. “The beauty of performing measurements with the Fidas® Fly 100 aerosol spectrometer on the HORUS octocopter lies in the fact that it enables us to fly up and down at the same spot in the cloud, time and time again,” says Dr. Möhler. He explained that this was a particularly important addition for the researchers that helped them to broaden their normal options.

For the measurements, particles were also collected on filters at the measurement station in the Arctic. From the data, a new method developed by Dr. Möhler and his group at KIT was used in the laboratory to filter out from the total collected aerosol particles the few ice-forming particles as a function of temperature. Afterwards, this data was then compared with the total aerosol amounts measured with Fidas® Fly in order to find out what proportion of ice-forming aerosols contributes to the formation of snow and precipitation. “The question is, how does the aerosol change further into the cloud, and are there different size distributions or amounts of aerosols under the cloud, in the cloud or above the cloud?” Dr. Möhler suspects that the larger particles in particular contribute to ice formation. In Karlsruhe, two students are currently working at the KIT Institute on an analysis of the collected filter samples. Dr. Möhler himself is evaluating the Fidas® data and will then amalgamate the data. On account of the fact that the “data and information are very new”, the results are due to be published.

2017-09_Finland_IMG_4137_Gerd.jpg Drone pilot Gerd Schaufelberger with the Fidas® Fly 100 on the HORUS multicopter from Airclip
Photo: Dr. Ottmar Möhler

The cloud researcher was particularly impressed with the combination of the Fidas® aerosol spectrometer with the HORUS multicopter from Airclip. “It looked really professional, and I think it is exactly the right kind of development that the people who are developing flight systems are getting together with the people who develop the measurement devices so that both developments can be coordinated.” According to Dr. Möhler, all the participants benefited from the international exchange during the measurements in Finland. “There were absolutely no secrets, everyone was really open in the way they worked together, and we were all interested in developing these things for science because we understand that we can break new ground here.”

Atmospheric aerosol research at KIT

The department for Atmospheric Aerosol Research of the Institute of Meteorology and Climate Research (IMK-AAF) at the Karlsruhe Institute of Technology (KIT) is headed by Professor Dr. Thomas Leisner. The Institute is conducting research particularly into the role of aerosols in climate systems, the water cycle and the environment. It operates the internationally renowned AIDA Aerosol and Cloud Simulation Chamber, which is used to investigate the impact of aerosols on climate, weather and the environment. In addition, the Institute also operates laboratories for aerosol and cloud research, takes part in field campaigns and performs numerical modeling of atmospheric aerosol processes.

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