Das Projekt "CLOUD" wird vom Umweltbundesamt gefördert und von Paul Scherrer Institut, Labor für Atmosphärenchemie durchgeführt. Im CLOUD-Projekt (Cosmics Leaving OUtdoor Droplets) soll der Einfluss von galaktischer kosmischer Strahlung auf die Wolken und damit auf das Klima untersucht werden. Zu diesem Zweck wurde am CERN eine spezielle Kammer erstellt, die es erlaubt, unter ultrareinen Bedingungen die hierfür relevanten Prozesse zu untersuchen. Es ist bekannt, dass mit stärkerer galaktischer kosmischer Strahlung eine höhere Ionendichte in der Atmosphäre entsteht. Es soll untersucht werden, inwiefern durch diese erhöhte Ionendichte die Nukleation neuer Aerosolpartikel begünstigt wird. Wenn diese Aerosolpartikel auf die Grösse von etwa 50 bis 100 nm anwachsen, können sie zu so genannten Wolkenkondensationskernen werden und damit die Wolkenbildung beeinflussen. Eine höhere Ionendichte könnte damit in einer Wolke zu mehr und dafür kleineren Wolkentröpfchen führen; eine solche Wolke hätte eine stärker abkühlende Wirkung. Umgekehrt würde die heute eher niedrige Intensität der galaktischen kosmischen Strahlung über diese Mechanismen zu einer Temperaturerhöhung führen. Einzelne Wissenschaftler schreiben die heutige Temperaturerhöhung diesem Effekt der galaktischen kosmischen Strahlung und weniger der Erhöhung der Treibhausgase zu. Das CLOUD-Projekt hat deshalb zum Ziel, diese Hypothese zu überprüfen. Am CERN kann eine erhöhte kosmische Strahlung durch einen Pionenstrahl vom Protonensynchrotron simuliert werden, so dass Ionendichten bis auf eine Höhe von 15 km eingestellt werden können. Weiter können die aus der galaktischen kosmischen Strahlung stammenden Ionen mit einem elektrischen Feld eliminiert werden, bevor sie einen Einfluss auf die Nukleation ausüben können, so dass auch die Nukleation unter vollständig neutralen Bedingungen untersucht werden kann. Das CLOUD-Konsortium verfügt über eine breite Expertise in der Charakterisierung von Gasen, Clustern, Aerosolpartikeln und Wolken und ist deshalb ideal geeignet, diese komplexe Fragestellung anzugehen.
Das Projekt "CERN-CLOUD project" wird vom Umweltbundesamt gefördert und von Paul Scherrer Institut, Labor für Atmosphärenchemie durchgeführt. CLOUD is an acronym for Cosmics Leaving OUtdoor Droplets. The scientific objective of CLOUD is to investigate the influence of galactic cosmic rays (GCRs) on ions, aerosols, cloud condensation nuclei (CCN) and clouds, with the CLOUD facility at CERN, and thereby to assess the significance of a possible 'solar indirect' contribution to climate change. Aerosols and clouds are recognised as representing the largest uncertainty in the current understanding of climate change. The Intergovernmental Panel on Climate Change (IPCC) estimates that changes of solar irradiance ('direct solar forcing') have made only a small (7Prozent) contribution to the observed warming. However, large uncertainties remain on other solar-related contributions, such as the effects of changes of galactic cosmic rays on aerosols and clouds. CLOUD aims to settle the important unanswered questions of the IPCC on possible cosmic ray effects on clouds and climate, and to help sharpen our understanding of the anthropogenic contribution to global warming. The scientific programme of CLOUD will involve the establishment of a central CLOUD facility in a beamline (T11) at the CERN Proton Synchrotron accelerator, comprising a large aerosol chamber, within which the atmosphere is recreated from ultra-pure air with added water vapour, trace gases under study and, for certain experiments, aerosols. The chamber will be equipped with a wide range of sensitive instruments to analyse their contents via optical ports or sampling probes. The accelerator provides an adjustable and precisely measurable beam of 'cosmic rays' that closely matches natural cosmic rays in ionisation density, uniformity and intensity, spanning the atmospheric range from ground level to the maximum around 15 km altitude. In contrast with experiments in the atmosphere, CLOUD will be able to compare processes when the cosmic ray beam is varied, and all experimental parameters can be precisely controlled and measured. More information is found at the CLOUD website http://cloud.web.cern.ch/cloud/.
Das Projekt "Modelling of aerosol effects in mixed-phase clouds" wird vom Umweltbundesamt gefördert und von Paul Scherrer Institut, Labor für Atmosphärenchemie durchgeführt. As summarised in the 4th IPCC report, the indirect effect of aerosols on cloud properties constitutes the single largest remaining uncertainty in the climate system. In this project, we propose to make use of a uniquely comprehensive set of observations, in combination with detailed microphysical modelling, to develop accurate ice nucleation parameterisations for different types of aerosol in mixed-phase clouds. Further, we will use the combination of a detailed microphysical box model and a highly resolved three-dimensional model (the weather research and forecasting model, WRF) with spectral bin microphysics, to determine which dynamical processes need to be accounted for, in order to accurately represent the cloud microphysical properties. One of our main objectives in this work, which makes this project novel and original, is to contribute to the resolution of the recent controversy surrounding the efficiency of black carbon aerosol as an ice nucleus. The development of model parameterisations of ice nucleation in clouds is often hampered by the necessity to base the parameterisations on idealised laboratory experiments, and by the paucity of cloud microphysical measurements suitable for model validation. However, this project is in a unique position to benefit from several observational data sets gathered during recent measurement campaigns. The observations on which we will base the modelling work are performed at the high altitude Swiss research station on the Jungfraujoch and provide a highly detailed description of the physical and chemical properties of the ice nucleating aerosol particles in ambient clouds. In addition, they describe the microphysical properties of the observed clouds. The measured aerosol properties give us the benefit of being able to initialise the models with the actual aerosol found in the clouds, rather than an idealised background aerosol derived from emission inventories or large scale models. The observed cloud microphysical properties will allow us to constrain and validate the model simulations in exceptional detail. The models will be tested in their original form, with their existing microphysical parameterisations, and these will then be further developed until the models can represent the observed cloud properties. Special attention will be given to the roles of black carbon (BC) aerosol, because of its anthropogenic source, and the uncertainty surrounding its activity as an ice nucleus (IN) and to mineral dust, because of its high IN activity. We will further use the combination of models and observations to try to identify other important IN components in the observed aerosol, such as biogenic particles or organic species. (...)
Das Projekt "FORCE Proposal to Investigation of Secondary Organic Aerosol Formation in the PSI Smog Chamber and at CERN" wird vom Umweltbundesamt gefördert und von Paul Scherrer Institut, Labor für Atmosphärenchemie durchgeführt. The scientific objective of CLOUD is to investigate the influence of galactic cosmic rays (GCRs) on ions, aerosols, cloud condensation nuclei (CCN) and clouds, with the CLOUD facility at CERN, and thereby to assess the significance of a possible 'solar indirect' contribution to climate change. Aerosols and clouds are recognised as representing the largest uncertainty in the current understanding of climate change. The Intergovernmental Panel on Climate Change (IPCC) estimates that changes of solar irradiance ('direct solar forcing') have made only a small (7Prozent) contribution to the observed warming. However, large uncertainties remain on other solar-related contributions, such as the effects of changes of galactic cosmic rays on aerosols and clouds. CLOUD aims to settle the important unanswered questions of the IPCC on possible cosmic ray effects on clouds and climate, and to help sharpen our understanding of the anthropogenic contribution to global warming. We have established a central CLOUD facility in the beamline T11 at the CERN Proton Synchrotron accelerator, comprising a large aerosol chamber, within which the atmosphere is recreated from ultra-pure air with added water vapour, trace gases under study and, for certain experiments, aerosols. The chamber is equipped with a wide range of sensitive instruments to analyse their contents via optical ports or sampling probes. The accelerator provides an adjustable and precisely measurable beam of 'cosmic rays' that closely matches natural cosmic rays in ionisation density, uniformity and intensity, spanning the atmospheric range from ground level to the maximum around 15 km altitude. In contrast with experiments in the atmosphere, CLOUD is able to compare processes when the cosmic ray beam is varied, and all experimental parameters can be precisely controlled and measured. More information is found at the CLOUD websites