Atmosphere and Climate
Human activities – in particular the increasing levels of energy production and consumption – and also natural activities release large quantities of trace substances, thus influencing the composition of the atmosphere and the climate.
Since the beginning of industrialization in the 19th century, the chemical composition of the air has changed significantly and today exhibits significantly higher levels of trace substances. This has two important consequences for the Earth system and human society. On the one hand, the trace substances influence the Earth’s radiation budget and climate, while on the other hand, megacities and industrialized nations in particular suffer from higher levels of pollution leading to adverse effects on human health, damage to ecosystems, and poor harvests.
At the Institute of Energy and Climate Research (IEK), scientists investigate the physical and chemical processes in the atmosphere as well as their interactions in the entire climate system. In doing so, one of the aims is to understand the precise impact of human influences on air quality and the climate. With the aid of their experimental findings and computer simulations, Jülich researchers continue to develop existing climate models, act as experts, and draw up recommended actions for policymakers.
Trace substances in the troposphere
The Institute of Energy and Climate Research – Troposphere (IEK-8) is focused on the layer of atmosphere directly above the Earth’s surface – this includes the air that we breathe. The physical and chemical processes in the troposphere which have a significant influence on the chemical composition of the air comprise the subinstitute’s focus of research. This includes the release of trace substances from natural sources at the Earth’s surface such as plants, transport and industry, and the chemical conversion of trace substances in the atmosphere, as well as the formation and distribution of trace substances in the air.
One major focus of research is on the long-term observation of trace substances and their role in the climate system. This also includes water vapour, carbon dioxide, methane, and ozone. Many interactions that are important for reliable weather predictions and climate models remain unclear. The processes that control the atmosphere’s self-purifying capacity vary, for example, according to climate zone, time of day and night, and season, as well as whether the airspace is above a megacity like Beijing or above large forested areas.
The formation and lifespan of health- and climate-relevant aerosols such as particulate matter and ozone are also subject to these changes.
Understanding these interactions is key to classifying and predicting human-induced influences on the climate and air quality as well as being able to provide reliable recommendations for political measures.
At the Institute of Energy and Climate Research – Stratosphere (IEK-7), scientists investigate the chemistry, dynamics, and microphysics of the layers adjoining the troposphere. These layers comprise the tropopause region, a layer of the Earth’s atmosphere between the troposphere and the stratosphere – at roughly 7 to 14 kilometres in altitude – and the adjacent stratosphere at between 15 and 50 kilometres in altitude. Here, the scientists similarly aim to discover the exact processes taking place at this altitude and between the different layers as well as the role that these processes play in the Earth’s climate system.
The speed of the circulation of air masses between the tropics and polar latitudes, for example, provides scientists with indications regarding just how quickly climate change is progressing. In order to obtain an accurate picture in this respect, the mixing effects at different altitudes need to be investigated and considered in computer simulations.
Comparisons of the measurement data with the calculated data from simulations indicate to the researchers where they have been accurate with their models and where there are still some discrepancies, that is to say where interactions need to be looked at more closely.
Instruments take off
In order to obtain data that are as comprehensive and informative as possible, the Jülich climate researchers coordinate or participate in measurement campaigns that take into account the various issues of atmospheric research. In the European project PEGASOS, for example, international teams of scientists measured the composition of the air and their flows in the troposphere above Europe using a zeppelin. In the IAGOS project, the composition of the air is recorded via measuring instruments on board of commercial aircraft.
In higher regions, however, weather balloons and special aircraft such as Geophysica are used in order to clarify processes on predominantly local and regional scales.
The Jülich atmospheric researchers also draw on the use of satellite data, which play a particularly important role in the study of global connections.
More on the PEGASOS project with the Zeppelin NT
Atmosphere simulation chamber SAPHIR
In order to conduct in-depth research into the interactions in the atmosphere, it is important that the processes occurring in the air can be recreated in a controlled environment and in a manner that is both comprehensible and reproducible. The atmosphere simulation chamber SAPHIR at Forschungszentrum Jülich serves this very purpose. In this tube-shaped laboratory, scientists are able to accurately "compose" an artificial atmosphere under precise conditions by introducing high-purity gases. They are then able to observe how secondary pollutant gases and particles form.
The plant chamber SAPHIR-PLUS is able to supply a natural mixture of biogenic hydrocarbons for experiments if required. In combining both chambers, researchers can investigate what happens to the volatile hydrocarbons that plants emit into the air and what impact these emissions have on the atmosphere’s self-purifying capability and on air quality.
Simulation laboratory for climate research
A considerable proportion of climate research at Jülich takes place at the computer: measured data are evaluated, numerical models developed for equations, and model processes simulated and plotted in graphs.
For applications requiring high computing power and sophisticated algorithms, Jülich climate researchers can call on the support of experts from the Jülich Supercomputing Centre (JSC), specifically the Simulation Laboratory (SimLab) Climate Science team. The software engineers and data analysts are specialized in adjusting and optimizing calculations on supercomputers according to the researchers’ specific needs. These include highly specialized algorithms and requirements with respect to data transfer and storage.
As the requirements vary according to research field, JSC operates several simulation laboratories. The Jülich SimLab experts often come from the scientific field they supervise and conduct their own research themselves so as to provide their scientific clients with optimum support on current issues.
Video (in German): Climate research simulations. Scientists use Jülich supercomputers to conduct climate-related simulations: in order to reconstruct the distribution of gravity waves in the atmosphere, demonstrate the impact of wildfires on the climate, and to better understand the spread of volcanic aerosols after volcanic eruptions.
Support for the community
The SimLab Climate Science team not only supervises atmospheric researchers as well as soil and plant researchers on campus, but also provides climate research support to the scientific community beyond Jülich. The computing specialists contribute to international projects, for example the European Space Agency. They also collaborate closely with the SimLab Climate and Environment team at the Karlsruhe Institute of Technology (KIT).
An international team of researchers, in which experts from Jülich’s SimLab Climate Science team were involved, were unexpectedly able to measure gravity waves in the upper atmosphere using the NASA satellite Suomi National Polar-Orbiting Partnership – an accidental discovery for climate research. Gravity waves are oscillations of air that propagate sideways and upwards into further layers of the Earth’s atmosphere. Such waves are created in a stable atmospheric layer if the latter is disrupted by external stimuli, such as tropical storms, heavy thunderstorms, or simply by air flowing over a mountain ridge. The team of international researchers has now observed for the first time how the eruption of a volcano also triggers such waves. It is already known that they have an impact on climatic phenomena such as fluctuations of monsoon rain, El Niño events, and the formation of polar stratospheric clouds. If their impact can now be better assessed, experts will be able to more precisely define the models used by climate researchers.
We provide information on the latest research results in the field of atmospheric research through press releases, notifications, and in the Annual Report.
A Climate of Change? Forschungszentrum Jülich’s effzett magazine on climate research (3/2015): A Climate Of Change? (PDF, 4 MB)