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Suspended Particles

Mathematician Prof. Christine Böckmann examines particle movements
LIDAR of the research station in Ny Ålesund on the island of Spitsbergen.

LIDAR of the research station in Ny Ålesund on the island of Spitsbergen.

Air pollution inexorably belongs to our everyday life. The causes for this are complex, including volcanic eruptions and fires as well as industrial emissions. To examine the impact we need not only natural scientists like physicists but also mathematicians. Prof. Christine Böckmann is among those who deal with mathematical methods for inverse problems and their application in atmospheric research.

After Böckmann had finished her studies of mathematics she wanted to do applied research. “I did not want to stop at the mathematics I had studied.” And so she turned her attention to numerical mathematics. Already in her dissertation she developed algorithms that could be applied in natural sciences. Now she is concentrating on the interdisciplinary research in the topical field of parameter identification for aerosol particles in the atmosphere, which play an essential role in global warming and cooling. Böckmann’s ability to pursue mathematical theory and application at the same high level of quality has been greatly valued among experts.

By the 1990s, the scientist had already taken part in a project funded by the Federal Ministry of Research. This project dealt with mathematical methods for solving specific problems in the industrial and business sectors. This was when she started collaborating with the regional LIDAR group of Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI) in Potsdam. The group uses its technology to observe climatic development in the Artic, in Ny-Ålesund on Spitsbergen. A LIDAR (“light detection and ranging”) system is an optical radar that sends pulsed laser beams of different wavelengths into the atmosphere, where air molecules and tiny floating particles – the aerosol particles – scatter the electromagnetic radiation. The intensity of the reflected light is measured dependent on time. From a mathematical point of view, “it is a non-linear inverse scattering problem. Inverse means that the size distribution of the aerosol can be determined indirectly by the laser light reflected on the particles and captured by a detector”, Böckmann explains. Her team had to deal with the “inverse scattering problem” when they first started their collaboration.

The use of LIDAR technology for atmospheric remote sensing turned out to be successful. Using a model, the mathematicians calculated other microphysical particles properties from the optical data and measured LIDAR signals. Since this problem is also relevant for studying global warming, the German LIDAR-Netz developed into a Europe-wide network. In 2000, EARLINET (European Aerosol Research Lidar Network) was established, followed by EARLINET-ASOS (European Aerosol Research Lidar Network – Advanced Sustainable Observation System). The scientists’ main goal has been to compile a comprehensive database for the aerosol distribution on a continental scale.

Böckmann’s PhD student Lukas Osterloh had the opportunity to conduct an extensive simulation study on parallel computers at the Supercomputing Center in Barcelona, which would have taken years with the technology available in Potsdam. The mathematical model was able to be optimized and the relevant software has since been developed. During the first stage, the scientists determined microphysical parameters for spherical particles from the optical LIDAR-profiles. Later they managed to extend the one-dimensional model to a two-dimensional one.

“The aerosols we observe decisively influence weather and climate”, Böckmann says. When analyzing climate models they examine not only aerosol particles but also clouds. To improve these models, scientists of the “aerosol-group” joined forces with those of the “climate-group”. They want to inspire young people to grapple with these new ideas. This is how funding was raised for a project within the Marie Curie Actions at the EU. The aim of the four-year project is the training of young doctoral candidates and postdocs for atmospheric remote sensing (ITARS – Initial Training for Atmospheric Remote Sensing). It started in April 2012 and includes ten groups from various countries, one of which works at the University of Potsdam.

The effects of the 2010 eruption of volcano Eyjafjallajökull reached far beyond Iceland. The volcanic ash thrown up in the atmosphere disrupted air travel to an unprecedented extent in much of northern and central Europe. The optical radar LIDAR can help identify the particles in volcanic ash. This has a practical advantage because the ash is not a problem for air travel per se. Only certain types of particles are “harmful” to aircraft engines. In any case there are always more non-spherical particles, i.e. those which do not have a spherical shape but any other shape. The mathematical models used so far have not been applicable. The aim is to develop new ones for non-spherical particles, for example from Sahara dust or volcanic clouds. For this you need a database of the scattering properties of such particles.

The scientists first want to analyze the reaction of the mathematical models on non-spherical particles but the mathematicians are still only at the beginning here. Böckmann calls it a generation project. The question is also of great interest for her because sending particles into the atmosphere to influence the climate, for example to decrease the temperature or to produce rain, is being considered. Questions of ethical and legal consequences do however cloud this issue. Against this – eminently practical – background it is important for Böckmann to continue her work on the project. “I think we are not yet at the point where we can foresee the consequences of such interventions into nature.”

The Project

Initial Training for Atmospheric Remote Sensing
Participants: Groups from Romania, Greece, Spain, Italy, Great Britain, the Netherlands, and Germany as well as five small- and medium-sized companies from Greece, Italy, France, and Germany
Duration: 2012–2016
http://itars.uni-koeln.de

The Scientist

Prof. Dr. Christine Böckmann studied mathematics in Dresden. She did her doctorate at the Dresden University of Technology in 1984 and habilitated at the University of Potsdam in 2002. She is an associate professor at the Institute of Mathematics at the University of Potsdam. Her research interests include the numerics of inverse problems and applications in atmospheric physics.
Contact
Universität Potsdam
Institut für Mathematik
Am Neuen Palais 10
14469 Potsdam
E-Mail: christine.boeckmann@uni-potsdam.nomorespam.de

Text: Dr. Barbara Eckhardt
Translation: Susanne Voigt
Online-Editing: Silvana Seppä