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Any Earth system research (e.g. change of atmospheric dynamics, Earth’s radiation budget, water and carbon cycles, atmospheric chemistry or weather prediction) requires accurate measurements of the state of the atmosphere on global scale. In connection with passive remote sensing, active sensors on satellites, as Lidar and Radar instruments, provide powerful tools for generation of the required data products. The three European satellite missions MERLIN, ADM-Aeolus and EarthCARE make use of novel Lidar and Radar instruments, which are worldwide unique. MERLIN aims on investigation of the methane cycle, ADM-Aeolus serves to improve numerical weather forecast, and the objective of EarthCARE is the investigation of the cloud-aerosol-radiation interaction for the Earth’s radiation budget.
Aeolus, DISC and campaigns
The knowledge of wind speed is crucial for both weather forecasting and the understanding of atmospheric dynamics. In August 2018 the European Space Agency (ESA) has launched the Earth Explorer Satellite Aeolus into space. It carries the revolutionary instrument ALADIN - the first European lidar and the world's first Doppler wind lidar in space.
Solar radiation drives atmospheric circulation and hence weather and climate. Accurate knowledge about solar and terrestrial radiation and their interaction with clouds, aerosol particles, and trace gases is therefore required for the determination of the Earth’s radiation budget that controls climate. The EarthCARE satellite mission, to be launched by ESA in 2018, is expected to provide new insights into aerosol-cloud-radiation interactions thanks to simultaneous active and passive observations of the Earth’s atmosphere.
Knowledge about the emissions of methane is of great importance for climate prediction. Large uncertainties exist in the assessment of tropical and boreal wetlands, which comprise the largest natural sources. By using lidar measurements of atmospheric methane, the mission MERLIN is expected to significantly improve our knowledge of natural and anthropogenic methane emissions on a global basis.
Atmosphere, Weather and Clima
Earth observation and the interpretation of data with help of numerical models are two cornerstones of climate change research.
The global climate is changing. According to IPCC a large fraction of this change is anthropogenic due to the emissions of greenhouse gases, their precursors or other directly and indirectly radiatively active substances (e.g., water vapour from aircraft, which triggers contrails).
Clouds, aerosols and climate
The role of clouds and aerosols in the climate system is still one of the largest uncertainties in the prediction of the future development of climate and in the understanding of the water cycle. Broadening the knowledge about cloud and aerosol processes will not only deepen our understanding of the climate system, but it is an essential prerequisite to assessing the climate effects of transport emissions.
Detailed investigations of the variability of the stratospheric ozone layer and its long-term changes have shown that a full description of the observed fluctuations is only possible if dynamical as well as physical and chemical processes and their complex interactions are considered. Moreover, it must be regarded that changes in the troposphere in general also lead to modifications of the stratospheric composition and specifically of the ozone layer.
Water vapour and ozone in the atmosphere
Identification, explanation and quantification of variations of climate relevant atmospheric trace gases, in particular ozone and water vapour, but also of UV radiation and climate, are central tasks of atmospheric research.
Earth System Model Evaluation
Earth System Model (ESM) evaluation is performed to assess the performance of a model either against predecessor versions, a wider set of other models or against observations. The evaluation of ESMs with observations is crucial for model improvements and an improved process understanding of the climate system. It is also a vital prerequisite for more trustworthy climate projections of the 21st century needed as basis for guidelines in climate policy.
Investigation of atmospheric gravity waves
Gravity waves are primarily excited in the lower atmosphere, e.g. by flow over mountains. They propagate horizontally and vertically and transport energy and momentum over large distances. Gravity waves also interact with the background flow, and seasonal variations in the atmospheric wind field modulate gravity wave propagation. The deposition of energy and momentum in the atmosphere by breaking gravity waves modifies the thermal structure of the atmosphere as well as the circulation.
Radiation in the ultraviolet part of the solar spectrum from 280 to 400 nanometer (nm), especially at the shorter UV-B wavelengths from 280 to 315nm, is potentially harmful to humans, animals, and plants. Sunburn is considered as one of the main causes for irreparable damages of the human skin and for the incidence of skin cancer.
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