Evidences for a quasi 60-year North Atlantic Oscillation since 1700 and its meaning for global climate change

The North Atlantic Oscillation (NAO) obtained using instrumental and documentary proxy predictors from Eurasia is found to be characterized by a quasi 60-year dominant oscillation since 1650. This pattern emerges clearly once the NAO record is time integrated to stress its comparison with the temperature record. The integrated NAO (INAO) is found to well correlate with the length of the day (since 1650) and the global surface sea temperature record HadSST2 and HadSST3 (since 1850). These findings suggest that INAO can be used as a good proxy for global climate change, and that a 60-year cycle exists in the global climate since at least 1700. Finally, the INAO ~60-year oscillation well correlates with the ~60- year oscillations found in the historical European aurora record since 1700, which suggests that this 60-year dominant climatic cycle has a solar-astronomical origin

Measurement of the charging state of 4-70 nm aerosols

The charging state of aerosols in an 8 m3 reaction chamber was measured using an electrostatic classifier with a condensation particle counter at different levels of ionization in the chamber. By replacing the Kr-85 neutralizer in the classifier with a radioactively neutral dummy we were able to measure only the aerosols that were charged inside our reaction chamber. These measurements were then compared with measurements using the neutralizer to get the charging state of the aerosols, which refers to the charged fraction of the aerosols compared to an equilibrium charge distribution. Charging states were measured for both positively and negatively charged aerosols while the ionization in the chamber was varied using external gamma sources. We find that the negatively charged aerosols were overcharged (relative to the equilibrium) by up to about a factor of 10 below 10 nm and at 16±2% from 10 to 70 nm. At higher levels of radiation on the chamber the smaller aerosols were less overcharged while the large aerosols were more overcharged (23±2%). For the positively charged aerosols only the smallest aerosols were overcharged while those over 10 nm were undercharged (relative to the equilibrium) by 21±3%. Increasing the radiation on the chamber increased the undercharge above 10 nm to 25±2% while the overcharge below 10 nm disappeared. The split between positive and negative charges above 10 nm can be explained by differences in mobility of small negative and positive ions. The overcharge below 10 nm can be explained by ions participating in the formation of aerosols of both signs, while the reduction in this overcharge at higher levels of ionization may be explained by faster recombination

The response of clouds and aerosols to cosmic ray decreases

A method is developed to rank Forbush decreases (FDs) in the galactic cosmic ray radiation according to their expected impact on the ionization of the lower atmosphere. Then a Monte Carlo bootstrap-based statistical test is formulated to estimate the significance of the apparent response in physical and microphysical cloud parameters to FDs. The test is subsequently applied to one ground-based and three satellite-based data sets. Responses (&gt;95%) to FDs are found in the following parameters of the analyzed data sets. AERONET: &#xC5;ngstr&#xF6;m exponent (cloud condensation nuclei changes), SSM/I: liquid water content, International Satellite Cloud Climate Project (ISCCP): total, high, and middle, IR-detected clouds over the oceans, Moderate Resolution Imaging Spectroradiometer (MODIS): cloud effective emissivity, cloud optical thickness, liquid water, cloud fraction, liquid water path, and liquid cloud effective radius. Moreover, the responses in MODIS are found to correlate positively with the strength of the FDs, and the signs and magnitudes of the responses agree with model-based expectations. The effect is mainly seen in liquid clouds. An impact through changes in UV-driven photo chemistry is shown to be negligible and an impact via UV absorption in the stratosphere is found to have no effect on clouds. The total solar irradiance has a relative decrease in connection with FDs of the order of 10&#x2212;3, which is too small to have a thermodynamic impact on timescales of a few&#xA0;days. The results demonstrate that there is a real influence of FDs on clouds probably through ions.</p

Increased ionization supports growth of aerosols into cloud condensation nuclei.

Ions produced by cosmic rays have been thought to influence aerosols and clouds. In this study, the effect of ionization on the growth of aerosols into cloud condensation nuclei is investigated theoretically and experimentally. We show that the mass-flux of small ions can constitute an important addition to the growth caused by condensation of neutral molecules.&#xA0;Under atmospheric conditions the growth from ions can constitute several percent of the neutral growth. We performed experimental studies which quantify the effect of ions on the growth of aerosols between nucleation and sizes &gt;20&#x2009;nm and find good agreement with theory. Ion-induced condensation should be of importance not just in Earth's present day atmosphere for the growth of aerosols into cloud condensation nuclei under pristine marine conditions, but also under elevated atmospheric ionization caused by increased supernova activity

The ION-CAGE code: A numerical model for the growth of charged and neutral aerosols

The presence of small ions influences the growth dynamics of a size distribution of aerosols. Specifically, the often neglected mass of small ions influences the aerosol growth rate, which may be important for terrestrial cloud formation. To this end, we develop the Ion and Charged Aerosol Growth Enhancement (ION-CAGE) code, a numerical model to calculate the growth of a species of aerosols in the presence of charge, which explicitly includes terms for ion condensation. It is shown that a positive contribution to aerosol growth rate is obtained by increasing the ion-pair concentration through this ion condensation effect, consistent with recent experimental findings. The ion condensation effect is then compared to aerosol growth from charged aerosol coagulation, which is seen to be independent of ion-pair concentration. Growth rate enhancements by ion condensation are largest for aerosol sizes less than ∼25 nm and increases proportional to the ion concentration. The effect of ion condensation is expected to be most important over pristine marine areas. The model source code is made available through a public repository

Ultra-violet absorption cross sections of isotopically substituted nitrous oxide species: 14N14NO, 15N14NO, 14N15NO and 15N15NO

The isotopically substituted nitrous oxide species 14N14NO, 15N14NO, 14N15NO and 15N15NO were investigated by ultra-violet (UV) absorption spectroscopy. High precision cross sections were obtained for the wavelength range 181 to 218 nm at temperatures of 233 and 283 K. These data are used to calculate photolytic isotopic fractionation constants as a function of wavelength. The fractionation constants were used in a three-dimensional chemical transport model in order to simulate the actual fractionation of N2O in the stratosphere, and the results were found to be in good agreement with field studies

Ultra-violet absorption cross sections of isotopically substituted nitrous oxide species: (NNO)-N-14-N-14, (NNO)-N-15-N-14, (NNO)-N-14-N-15 and (NNO)-N-15-N-15

The isotopically substituted nitrous oxide species (NNO)-N-14-N-14, (NNO)-N-15-N-14, (NNO)-N-14-N-15 and (NNO)-N-15-N-15 were investigated by ultra-violet (UV) absorption spectroscopy. High precision cross sections were obtained for the wavelength range 181 to 218 nm at temperatures of 233 and 283 K. These data are used to calculate photolytic isotopic fractionation constants as a function of wavelength. The fractionation constants were used in a three-dimensional chemical transport model in order to simulate the actual fractionation of N2O in the stratosphere, and the results were found to be in good agreement with field studies