The atmosphere plays a central role for the environmental conditions on earth. Yet, our understanding of the system “atmosphere” still is incomplete and predictions concerning the development of the climate are subject to large uncertainties. Therefore, it is the defined objective of the Atmosphere and Climate Program to better understand the complex interactions among the partial systems of the atmosphere and with other parts of the earth system. An interdisciplinary and integrated approach is pursued, with laboratory studies, field measurement campaigns, and long-term observations of the atmosphere being combined with model simulations. These activities are embedded in current national and international research programs. The main share in the Program is assumed by the Institute of Meteorology and Climate Research with its four divisions. Other partners involved are the Institute for Applied Computer Science and the Institute of Data Processing and Electronics. These institutes are supported by the unique infrastructure of the Research Center. Work concentrates on the following issues:

Regional change of water availability is one of the most vital consequences of climate change. Therefore, the need for scientifically sound assessments of regional climate and water cycle change scenarios is rapidly growing. Based on extensive measurements, research focuses on representing the atmospheric components of the water cycle, in particular clouds and convection in their dynamic environment, in a realistic way in regional high resolution climate models and in weather forecast models, and on validating the results by advanced statistical analysis.

The research aims at enhanced predictive understanding of biospheric, hydrospheric and atmospheric (BHA) interactions, including their response to global climate and land-use change. The focus is on the regional scale in climatically sensitive, and socio-economically significant regions, such as mountain areas, semi-arid regions, conurbations (megacities). To achieve this overarching goal, fundamental processes from the molecular scale, extended ecosystems, to the regional scale is studied. Work is based on manipulative experiments, instrument development, as well as observational and modelling techniques. Synthesis of process ensembles across scales is achieved by massively coupled BHA-climate models, as the basis for climate change impact studies, to study the regional expression of global climate change scenarios on water resources, air quality, tourism, agro- and silviculture.

The change in tropospheric air composition is connected with growing industrialization and urbanization, developing megacities, increasing traffic, and general land-use change. It has resulted in changing emissions of primary trace gases and aerosols into the troposphere, with direct impact on atmospheric chemical processes that control the removal of greenhouse gases and pollutants from the atmosphere (atmospheric self-cleaning), but also the chemical formation of new pollutants in the atmosphere like ozone or secondary organic aerosols (SOA). Continuous and long-term measurements monitor the state of the atmosphere and its changes over time. The chemical and microphysical processes of anthropogenic and biogenic trace substances and their effect on the self cleaning capability, the formation of aerosol, and the radiation balance in the troposphere are investigated. The overall goal is to improve the predictability of the atmospheric chemical state in a changing climate.

The upper troposphere / stratosphere (UTS) region plays a key role in the climate system. Changes in the structure and chemical composition of the lower part of this region (UTLS) result in particularly large changes in the so-called radiative forcing of the atmosphere, which trigger climate change. In spite of its immense significance, the UTLS region is one of the least understood regions of the atmosphere. This is a result of its great dynamical, microphysical and chemical complexity. Research is performed to provide detailed knowledge about the role of the UTS in the Earth system, in particular in the context of climate change and climate variability. The focus is on meso-scale processes and their occurrence at the global scale. The envisaged scientific analyses are based on the synergetic use of airborne instruments, satellite observations, and regional as well as global atmospheric models.