CLOUD: an atmospheric research facility at CERN

This report is the second of two addenda to the CLOUD proposal at CERN (physics/0104048), which aims to test experimentally the existence a link between cosmic rays and cloud formation, and to understand the microphysical mechanism. The document places CLOUD in the framework of a CERN facility for atmospheric research, and provides further details on the particle beam requirements

Addendum to the CLOUD proposal

This report is the first of two addenda to the CLOUD proposal at CERN (physics/0104048), which aims to test experimentally the existence a link between cosmic rays and cloud formation, and to understand the microphysical mechanism. The document provides further details on the detector design, scientific motivation and experimental programme

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

Candidate Gene Screen in the Red Flour Beetle Tribolium Reveals Six3 as Ancient Regulator of Anterior Median Head and Central Complex Development

Several highly conserved genes play a role in anterior neural plate patterning of vertebrates and in head and brain patterning of insects. However, head involution in Drosophila has impeded a systematic identification of genes required for insect head formation. Therefore, we use the red flour beetle Tribolium castaneum in order to comprehensively test the function of orthologs of vertebrate neural plate patterning genes for a function in insect head development. RNAi analysis reveals that most of these genes are indeed required for insect head capsule patterning, and we also identified several genes that had not been implicated in this process before. Furthermore, we show that Tc-six3/optix acts upstream of Tc-wingless, Tc-orthodenticle1, and Tc-eyeless to control anterior median development. Finally, we demonstrate that Tc-six3/optix is the first gene known to be required for the embryonic formation of the central complex, a midline-spanning brain part connected to the neuroendocrine pars intercerebralis. These functions are very likely conserved among bilaterians since vertebrate six3 is required for neuroendocrine and median brain development with certain mutations leading to holoprosencephaly

Massive Positive and Negative Chemiions in the Exhaust of an Aircraft Jet Engine at Ground Level: Mass Distribution Measurements and implications for Aerosol Formation

Mass distributions of positive and negative chemiions (CI) were measured in the exhaust plume of an aircraft jet engine at the ground at exhaust gas ages around 0.1 s using an ion mass spectrometer with a mass range of 8500 amu (large ion mass spectrometer, LIOMAS). Most of the CI had mass numbers m < 2000, but very massive CI with m up to at least 8500 were also observed. About 1% of the negative CI and 0.2% of the positive CI had in > 8500. An increase of the fuel sulfur content from 2 to 66 mg/kg did not change the ion mass distributions. This indicates that most of the observed CI did not contain sulfur- bearing molecules, but probably contained low volatility organic compounds (LVOC). An LVOC-emission index of 22.5 mg LVOC/kg fuel is inferred from our data. (C) 2002 Elsevier Science Ltd. All rights reserved

Cosmic ray-induced aerosol-formation: First observational evidence from aircraft-based ion mass spectrometer measurements in the upper troposphere

[1] Large positive cluster ions with atomic mass numbers up to 2500 have for the first time been detected in the upper troposphere using an aircraft-based large ion mass spectrometer (LIOMAS). Three ion families seem to be present (types 1, 2 and 3). Type 1 ions probably are H+BbWw (W is H2O and B is mostly acetone (CH3)(2)CO, and b less than or equal to 2). Type 2 ions are probably H(+)B(b)A(a)W(w) (A = H2SO4) formed by A- attachment to type 1 ions. Type 3 ions are probably very small charged aerosols formed preferably by type 1 ion attachment to stable electrically neutral A(x)W(y) clusters. The latter are preferably formed by ion-ion recombination. Hence our observations provide strong evidence for the ion-mediated formation and growth of aerosol particles in the upper troposphere

Cosmic ray-induced aerosol-formation: First observational evidence from aircraft-based ion mass spectrometer measurements in the upper troposphere

[1] Large positive cluster ions with atomic mass numbers up to 2500 have for the first time been detected in the upper troposphere using an aircraft-based large ion mass spectrometer (LIOMAS). Three ion families seem to be present (types 1, 2 and 3). Type 1 ions probably are H+BbWw (W is H2O and B is mostly acetone (CH3)(2)CO, and b less than or equal to 2). Type 2 ions are probably H(+)B(b)A(a)W(w) (A = H2SO4) formed by A- attachment to type 1 ions. Type 3 ions are probably very small charged aerosols formed preferably by type 1 ion attachment to stable electrically neutral A(x)W(y) clusters. The latter are preferably formed by ion-ion recombination. Hence our observations provide strong evidence for the ion-mediated formation and growth of aerosol particles in the upper troposphere

First Gaseous Ion Composition Measurements in the Exhaust Plume of a Jet Aircraft in Flight: Implications for Gaseous Sulfuric Acid, Aerosols, and Chemiions

Mass spectrometric composition measurements of gaseous negative ions have been made in the exhaust plume of a commercial jet aircraft (Airbus A310) in flight at altitudes around 10.4 km and at two plume ages around 3.0 and 3.6 s. Negative ions observed inside the exhaust plume are mostly NO3-(HNO3)m and HSO4-(HNO3)m with m ≤ 2. Outside the plume in the "background" atmosphere the same negative ion species with the same R = (HSO4-(HNO3)m)/(NO3-(HNO3)m) were observed. This indicates that the ions observed in the plume were entrained ambient atmospheric ions. By contrast no indications for negative chemiions (with masses ≤ 1100 amu) produced by the airbus engines were found in the plume. Furthermore our measurements indicate a modest decrease of the total concentration of entrained negative ions in the plume compared to the ambient atmosphere outside the plume. This decrease may be due to ion-removal by ion-attachment to aerosol-particles and/or ion-recombination with positive chemiions. We propose that the observed entrained ions can serve as probes for important plume components including gaseous sulfuric acid, aerosol particles and chemiions. Making use of this analytical potential we infer upper limits for the gaseous sulfuric acid concentration, total aerosol surface area density, and positive chemiion concentration. We conclude that initially formed gaseous sulfuric acid must have experienced rapid gas-to-particle conversion already in the very early plume at plume ages ‹ 1.6 s

Upper Tropospheric SO2 Conversion into Sulfuric Acid Aerosols and Cloud Condensation Nuclei.

Abstract not availableJRC.(EI)-Environment Institut