A study of the link between cosmic rays and clouds with a cloud chamber at the CERN PS

Recent satellite data have revealed a surprising correlation between galactic cosmic ray (GCR) intensity and the fraction of the Earth covered by clouds. If this correlation were to be established by a causal mechanism, it could provide a crucial step in understanding the long-sought mechanism connecting solar and climate variability. The Earth's climate seems to be remarkably sensitive to solar activity, but variations of the Sun's electromagnetic radiation appear to be too small to account for the observed climate variability. However, since the GCR intensity is strongly modulated by the solar wind, a GCR-cloud link may provide a sufficient amplifying mechanism. Moreover if this connection were to be confirmed, it could have profound consequences for our understanding of the solar contributions to the current global warming. The CLOUD (Cosmics Leaving OUtdoor Droplets) project proposes to test experimentally the existence a link between cosmic rays and cloud formation, and to understand the microphysical mechanism. CLOUD plans to perform detailed laboratory measurements in a particle beam at CERN, where all the parameters can be precisely controlled and measured. The beam will pass through an expansion cloud chamber and a reactor chamber where the atmosphere is to be duplicated by moist air charged with selected aerosols and trace condensable vapours. An array of external detectors and mass spectrometers is used to analyse the physical and chemical characteristics of the aerosols and trace gases during beam exposure. Where beam effects are found, the experiment will seek to evaluate their significance in the atmosphere by incorporating them into aerosol and cloud models.Recent satellite data have revealed a surprising correlation between galactic cosmic ray (GCR) intensity and the fraction of the Earth covered by clouds. If this correlation were to be established by a causal mechanism, it could provide a crucial step in understanding the long-sought mechanism connecting solar and climate variability. The Earth's climate seems to be remarkably sensitive to solar activity, but variations of the Sun's electromagnetic radiation appear to be too small to account for the observed climate variability. However, since the GCR intensity is strongly modulated by the solar wind, a GCR-cloud link may provide a sufficient amplifying mechanism. Moreover if this connection were to be confirmed, it could have profound consequences for our understanding of the solar contributions to the current global warming. The CLOUD (Cosmics Leaving OUtdoor Droplets) project proposes to test experimentally the existence a link between cosmic rays and cloud formation, and to understand the microphysical mechanism. CLOUD plans to perform detailed laboratory measurements in a particle beam at CERN, where all the parameters can be precisely controlled and measured. The beam will pass through an expansion cloud chamber and a reactor chamber where the atmosphere is to be duplicated by moist air charged with selected aerosols and trace condensable vapours. An array of external detectors and mass spectrometers is used to analyse the physical and chemical characteristics of the aerosols and trace gases during beam exposure. Where beam effects are found, the experiment will seek to evaluate their significance in the atmosphere by incorporating them into aerosol and cloud models

Massenspektrometrische Spurengasmessungen in Abgasfahnen von Duesentriebwerken zur Untersuchung des Einflusses des Luftverkehrs auf die Atmosphaere Abschlussbericht

To estimate the influence of airtraffic on the atmosphere and climate, detailed knowledge is required about the composition, distribution, and the chemical and physical evolution of jet engine exhaust at cruise altitude, i.e., in the region of the upper troposphere, tropopause, and lower stratosphere. For this purpose we performed mass spectrometric measurements of trace gases (SO_2, H_2SO_4, HNO_3, HNO_2, HCN, (CH_3)_2CO, CH_3CN), ions, and aerosol particles directly behind aircraft at cruise altitude or at ground, as well as inside the North Atlantic flight corridor. The presence of sulfuric acid, in major part as an aerosol component, in the exhaust plume of an aircraft at cruise altitude could be demonstrated for the first time. The conversion efficiency of fuel sulfur to H_2SO_4 amounts to at least 0.4%. Increased concentrations of HNO_3, HNO_2, and SO_2 were also found in young exhaust plumes. The data indicate the conversion of about 1.3% of the NO_2 and NO formed by combustion to the respective acid by reaction with OH radicals. The total number of positive ions probably exceeds 10"9 cm"-"3 at the engine exit and steeply decreases with increasing plume age due to ion-ion recombination. Massive ions with masses up to above 8500 amu were detected already in the very young plume, i.e., at a distance of a few m behind the engine. The mass distributions of positive and negative ions differ markedly. The abundance of negative ions above 450 amu about 100 m behind an aircraft at cruise altitude is about 1000 times higher than in the background atmosphere. Large-scale measurements in the North Atlantic flight corridor did not reval significantly enhanced concentrations of trace gases. Polluted air masses, probably originating from the planetary boundary layer, were detected above the Atlantic. (orig.)SIGLEAvailable from TIB Hannover: DtF QN1(72,40) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman