Forum for Science, Industry and Business

New insights into cloud formation

Erika Sundén, researcher at the University of Gothenburg, Sweden, has studied how extremely small cloud particles can dispose of excess energy. This knowledge is necessary to understand processes in the atmosphere that affect global climate change.

The models that have been built to describe climate change contain a major source of uncertainty, namely the effects of clouds. The UN Intergovernmental Panel on Climate Change points out in its climate report for 2007 that new knowledge is needed in this field.

It is namely the case that clouds can act in two ways: they may be a mirror that reflects radiation from the sun back into space, and they may be a blanket that seals in the heat emitted by the Earth. Mapping the formation and dispersion of clouds may, therefore, be a key step in climate research.

“One important stage is understanding the fundamental properties of the particles involved”, says Erika Sundén, doctoral student at the Department of Physics, University of Gothenburg.

Ammonia may play an important role

Erika has studied small particles known as “clusters”, which contain between 3 and 300 molecules. One line of research has investigated how water clusters dissipate excess energy, and this will help to understand how water droplets grow and how they evaporate. These are the processes by which ice and liquid water are transformed into water vapour (gas).

Another line has investigated how the clusters are influenced by ammonia, which is an important component of the atmosphere.

“I investigated water clusters that contained a small fraction of ammonia, and compared these with pure water clusters. I was able to show that the ammonia contributed to the stability of the clusters, and prevented them evaporating so rapidly. It may be that ammonia plays an important role in the early stages of cloud formation”, she says.

Temperatures of -100 degrees

It is not easy to measure the heat capacity of clusters, and an important part of her research has been to develop a method that can be used in future studies. Put simply, you could say that she has created water clusters in air, drawn them into a vacuum, and then examined them as they disintegrate. This method led her to an unexpected discovery.

“The temperature inside these clusters was around -100 °C, so one would expect that their heat capacity would correspond to that of ice. Despite this, the heat capacity of medium-sized clusters was greater, intermediate between that of ice and liquid water. The importance of this for how clouds form will be the subject of further research”, she says.

New insights into space clouds

Erika Sundén presents in her thesis also studies into the cooling rate and radiation of carbon particles, which may be a component of space clouds. It has long been uncertain whether molecules can exist in the empty space between the stars and planets, since the density of atoms is so low. The first negatively charged carbon molecules were discovered in 2006, however, after which work has continued surveying the molecules that are present in space clouds.

“First radiation from space is measured, and then it’s a case of creating models that can explain the observations. We create in the lab charged molecules that may be present in these clouds, and investigate whether these molecules emit radiation and, if so, to what extent”, she says.

Erika Sundén’s thesis “Thermal Properties of Clusters and Molecules – Experiments on Evaporation, Thermionic Emission, and Radiative Cooling” was successfully defended on 24 February. It can be downloaded from: http://gupea.ub.gu.se/handle/2077/28349

Helena Aaberg | idw
Further information:
http://www.gu.se
http://gupea.ub.gu.se/handle/2077/28349

Im Focus: BAM@Hannover Messe: innovative 3D printing method for space flight

At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.

Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...

Im Focus: Molecules Brilliantly Illuminated

Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.

Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...